SiC Powder Binder Jetting 3D Printing Technology: A Review of High-Performance SiC-Based Component Fabrication and Applications

Abstract

Silicon carbide (SiC) materials have demonstrated promising application prospects in modern manufacturing due to their outstanding physical and chemical properties. With its process flexibility and formation feasibility, binder jetting 3D printing technology has become a crucial technical approach to meet the demand for mass production of complex, high-performance SiC components. Addressing the technical challenges of traditional manufacturing techniques in achieving high-quality, complex-shaped SiC components, this paper systematically reviews the application of binder jetting 3D printing technology in fabricating high-quality SiC-based ceramic components, with a particular focus on the regulation of key process parameters affecting SiC green body formation quality and the optimization of post-densification processes. Firstly, this paper elaborates on the powder pretreatment, green part formation process, and post-processing chain involved in this technology, establishes an evaluation index system for formation quality, and provides research directions for rapid prototyping of SiC powders. Secondly, it provides an in-depth analysis of the influence patterns of jetting parameters (e.g., jetting conditions, powder characteristics, binder properties) and various post-processing techniques on the quality of SiC-based components, along with optimization methods to enhance the dimensional accuracy and mechanical properties of 3D-printed SiC components. Furthermore, this paper systematically summarizes advanced characterization methods for evaluating formation quality and demonstrates the technology’s application potential across multiple industrial fields through representative engineering cases. Finally, it predicts the future development trends of this technology and discusses potential application expansion directions and key scientific issues in current research, aiming to provide theoretical references for promoting in-depth development of this technology.

1. Introduction

In recent years, with the rising status of intelligent manufacturing in national strategies, the large-scale development and application of additive manufacturing (AM) technology have become key drivers of industrial transformation upgrading and sustainable development. Binder jetting (BJ) technology was originally developed in the early 1990s by researchers at the Massachusetts Institute of Technology [1]. With the rise of industry 4.0, modern AM systems integrate computer-aided design and materials processing and encompass various formation technologies, making them a key research area that has been applied in fields such as medical pharmaceuticals [2], aerospace [3], and construction [4]. Numerous cases of and demands for AM applications demonstrate their vast development potential across various sectors. However, strengthening standardization and certification systems to ensure product quality and reliability [5], as well as optimizing printing parameters and strategies to improve efficiency and overcome size constraints while maintaining product quality [6], remain challenges that AM needs to address.

Additionally, ongoing exploration of new materials and processes will provide more options and broader applications, ultimately reducing production costs. In recent years, research on AM using ultrafine silicon carbide (SiC) powder has garnered widespread attention. With its outstanding properties, SiC offers more flexible, economical, and efficient solutions compared to traditional manufacturing, showing great potential in the industrialization of AM. Currently, SiC materials are widely used across multiple sectors due to their superior properties [7]. High saturated electron velocity and significantly enhanced thermal conductivity make SiC the foundation of most global production of green, blue, and ultraviolet light-emitting diodes [8], and it has applications in electric vehicles, photovoltaic power generation, rail transportation, data centers, and charging infrastructure. Moreover, SiC’s high thermal conductivity, hardness, excellent chemical corrosion resistance, and exceptional temperature tolerance make it suitable for use in high-temperature and harsh environments, such as in cladding for fusion reactors [9] and materials for aerospace engine combustion chamber liners, combustion chamber barrels, and nozzle guide vanes [10,11]. These achievements align with SiC’s outstanding theoretical and practical value, making the future of the SiC industry brighter than ever before.

However, conventional SiC manufacturing technologies are mostly based on powder processing techniques such as compression forming and isostatic pressing, which are usually limited to the production of geometrically simple components [12]. For SiC components with complex geometries, conventional technologies require expensive and time-consuming molds. In contrast, AM technology offers a new solution for producing complex SiC components, such as stereolithography (SLA) [13], digital light processing (DLP) [14], selective laser sintering (SLS) [15], material extrusion (MEX) [16], and binder jetting (BJ) [17]. Figure 1 illustrates the schematic diagrams of the forming processes for the SLA, SLS, DLP, and MEX technologies.

At the same time,

Table 1. Applications of different additive manufacturing technologies in SiC component fabrication.

Additive Manufacturing Method	Binding Mechanism	Forming Method	The Current State of SiC Component Manufacturing	Ref.
SLA	Photopolymerization (liquid resin is cured by light)	Layer-by-layer curing of resin	High resolution, suitable for small-scale, high-precision parts. Low density of green parts due to the low solid loading and the opacity of SiC powders to light.	[22,23]
DLP	Photopolymerization (liquid resin is cured by light using digital micromirror devices)	Layer-by-layer curing of resin using a digital projector	Higher resolution and suitable for large-sized parts. The limitations of the binder material result in poor mechanical strength and high-temperature resistance of SiC components.	[14,24]
SLS	Fusion (powder is fused using a laser beam)	Layer-by-layer sintering of powder	Capable of producing high-density and mechanically strong parts. Large thermal stresses may cause deformation of SiC components.	[25,26]
MEX	Fusion (material is extruded and fused layer by layer)	Material is extruded and fused layer by layer using a nozzle	Relatively cost-effective, especially suitable for large-scale production. The precision of small and complex geometric SiC components is relatively low.	[24,27]

presents the printing mechanisms of SLA, DLP, SLS, and MEX, as well as the current status of SiC component manufacturing.

Compared to the aforementioned additive manufacturing technologies, the unique process characteristics of binder jetting 3D printing (as illustrated in Figure 2) endow it with distinctive advantages in the fabrication of SiC components. BJ 3D printing uses raw powder materials in SiC component manufacturing that do not require special processing, greatly enhancing the applicability and efficiency of 3D printing. In printing complex geometries, the BJ process does not require support structures [28]. The powder material can be reused, thus improving powder utilization efficiency. Additionally, the BJ process is typically carried out at ambient temperature [29], which helps prevent defects caused by heat sources during the manufacturing of SiC components. Finally, the flexible configuration of multiple printheads in BJ 3D printing meets the requirements for printing high-precision SiC components. These unique advantages make BJ 3D printing technology a promising solution for SiC material fabrication, with extensive application potential.

Significant progress has been made in recent years in manufacturing complex SiC ceramic components using BJ 3D printing technology (as shown in Figure 3). However, with the increasing performance demands for SiC-based ceramic components in aerospace, nuclear energy, and other advanced applications, BJ 3D printing technology must continuously optimize its printing process to overcome inherent technical bottlenecks, thereby reinforcing its manufacturing advantages in these fields. In BJ 3D printing, the final performance of SiC components is jointly determined by the formation quality of the green body (mechanical strength and accuracy of the SiC green part) and the post-processing densification techniques. Therefore, the key to enhancing the performance of SiC components lies in systematically investigating the synergistic optimization of the green body printing process and post-processing techniques.

To address this research demand, this study systematically reviews parameter optimization affecting SiC green body formation (e.g., jetting conditions, powder characteristics, and binder properties), presents an overview of post-processing techniques (e.g., liquid silicon infiltration and chemical vapor infiltration), and outlines strategies for post-processing optimization in the context of SiC component fabrication via BJ 3D printing. This work aims to provide researchers and engineers with a systematic framework for better understanding the behavior of SiC powder during the BJ 3D printing process and identifying the key influencing factors and major challenges in improving the quality of the final printed components.

In the second section, we will present the manufacturing process flow of BJ 3D printing technology for SiC component fabrication, with a focused discussion on critical pre-printing parameters and equipment selection criteria (including binder type, powder particle size, printhead model, and printer model). Finally, by analyzing the key quality evaluation parameters for SiC BJ 3D printing, this section identifies the core aspects requiring prioritized attention to enhance printing quality.

The third section, based on a comprehensive literature review, first examines solution strategies and corresponding parameter optimization approaches for issues affecting the quality of SiC green parts, including nozzle clogging, suboptimal powder bed quality, and stair-stepping effects. The second subsection discusses the current state of densification processes in mainstream post-processing techniques, along with their improvement strategies. Finally, special attention is given to advanced quality inspection and characterization techniques currently employed in BJ 3D printing.

The fourth section will focus on successful industrial applications of SiC powder BJ 3D printing technology across various sectors, including the aerospace, automotive, chemical, and electronics industries. Through comparative analysis of the technical requirements and implementation paths in different application scenarios, we aim to highlight the feasibility and advantages of this technology in practical production. Additionally, we will explore the current technical and economic challenges, especially when compared with traditional manufacturing methods, and discuss how to achieve a balance between high performance and cost-efficiency to promote adoption of this technology in large-scale production.

The fifth and sixth sections explore the future development directions of BJ 3D printing technology in SiC ceramic manufacturing and summarize the main findings and insights of this paper. With the continuous advancement of 3D printing technologies, controlling the formation quality of SiC powder will become a key focus for future research in this field. We will also examine the potential of new materials, novel processes, and interdisciplinary research to drive the development of this technology and identify possible future research priorities and application trends. Through these discussions, this paper aims to provide theoretical foundations and practical guidance for the advancement of SiC powder 3D printing technology, promoting its broader application in industrial production.

2. Process Flow and Performance Indicators of Binder Jetting 3D Printing

To ensure the quality of SiC components fabricated by BJ 3D printing technology, it is essential to systematically master the complete BJ 3D printing process. This chapter elaborates on the working principles and process flow for manufacturing SiC components using BJ 3D printing technology, providing a comprehensive analysis of the influence mechanisms of powder particle size distribution, binder type, printing nozzles, and selection of different printer brands on the final quality of SiC components. Finally, this chapter reviews the key parameters affecting formation quality in BJ 3D printing, offering clear directions for process optimization to improve component performance.

2.1. Process Flow and Pre-Printing Parameter Selection for Binder Jetting of Silicon Carbide Components

The fabrication of SiC ceramic components via binder jetting additive manufacturing involves two critical processing stages: green part formation and densification post-processing. During the green part formation stage, SiC green bodies with predetermined geometries are fabricated in the printing chamber through precise control of the printing parameters. The mechanical strength of the green bodies at this stage primarily originates from temporary bonding networks formed by binder bridging effects, typically exhibiting high internal porosity that results in relatively low flexural strength. This porous structural characteristic renders the green bodies inadequate to meet the mechanical property requirements for structural ceramic applications. Consequently, appropriate densification post-processing is essential to transform the green bodies into final products possessing dense microstructures and satisfactory mechanical performance. Figure 4 demonstrates the step-by-step process for fabricating dense Si-SiC composite components through binder jetting 3D printing combined with liquid silicon infiltration (LSI) and phenolic resin impregnation and pyrolysis (PRIP) post-treatment. Initially, green parts with porous structures are fabricated using binder jetting 3D printing equipment (as shown in Figure 4a).

Subsequently, the green parts are placed in a vacuum device for phenolic resin impregnation, allowing the resin to uniformly infiltrate the pores of the SiC green parts, resulting in impregnated parts (as shown in Figure 4b).

Furthermore, the impregnated parts undergo curing treatment at 190 °C (as shown in Figure 4c), during which the phenolic resin undergoes polycondensation to form a three-dimensionally crosslinked stable structure, preventing part collapse during pyrolysis while maintaining the porous structure for subsequent LSI.

The cured parts are then subjected to pyrolysis at 1000 °C in an argon atmosphere (as shown in Figure 4d), where the phenolic resin within the pores of the cured parts thermally decomposes to form a continuous carbon scaffold, serving as a reactive precursor for subsequent LSI. The argon atmosphere effectively prevents carbon loss due to oxidation during pyrolysis and controls the pyrolysis rate.

Finally, the carbonized parts undergo LSI at 1500 °C under vacuum, where the liquid silicon reacts with the carbon precursor in the pores of the carbonized parts to form SiC structures, gradually filling the component’s pores (as shown in Figure 4e). After LSI, a small amount of residual silicon remains within the component, forming dense Si-SiC composite parts.

The particle size of the SiC powder and the binder system constitute two fundamental factors in the printing process, making their appropriate selection prior to printing critically important. Regarding powder particle size, current BJ 3D printers employed in practical production universally adopt a uniform layer thickness slicing strategy, maintaining consistent thickness across all powder layers. Existing studies have reported on the spreading and flow characteristics of layers with a thickness of three times the particle size [32] and two times the particle size [33], yet there is no consensus on the optimal relationship between layer thickness and particle size. However, it is important to note that the layer thickness should not be less than the maximum particle size of the powder [34] to meet the basic requirements for powder spreading and printing resolution. Moreover, while smaller powder particle sizes theoretically enable finer surface details of printed components through reduced layer thickness settings and corresponding binder jetting volume adjustments, decreasing particle size simultaneously induces powder agglomeration during spreading and other issues. When the powder particle size falls below 5 μm, spreading defects can significantly compromise printing quality [23]. Therefore, when pursuing enhanced surface detail resolution through particle size reduction, it is critical to maintain a minimum particle size threshold of 5 μm.

On the other hand, regarding the selection of binder systems, apart from some special cases where the binder is a type of solvent that facilitates particle fusion, mainly for polymers but also applied in magnesium powder studies [35], there are two primary binder methods: in-liquid binding and in-bed binding. Additionally, the in-bed binding mechanism is divided into dry pre-mixing and wet pre-mixing. In-liquid binding involves adding binder material to the printing solution and then spraying this binder solution onto the powder bed to adhere particles using the inherent viscosity of the solution [36]. Dry pre-mixing [37] involves using a grinder or ball mill to pre-mix ceramic and solid binder, followed by spraying a print liquid (usually water-based) onto the powder bed to react with the solid binder, creating a viscosity that binds the SiC particles together. Wet pre-mixing involves dissolving binder material in a solvent (e.g., water), then adding ceramic material to obtain a mixed slurry. The slurry is then spray-dried [38] or freeze-dried [39] and sieved, with a binding mechanism consistent with dry pre-mixing. Wet pre-mixing relies on the binder’s ability to evenly coat the powder, but, due to the poor hydrophilicity of SiC [40], the powder tends to agglomerate due to localized binder enrichment, potentially leading to reduced print quality; thus, the BJ manufacturing process for SiC powder opts for either in-liquid spraying or dry pre-mixing. Based on an extensive literature review, Du W et al. [41] systematically summarized the distribution of binder types employed in BJ 3D printing for ceramic component fabrication, with jetting in-place accounting for 51%, dry pre-mixing for 12%, wet pre-mixing for 25%, and not-specified types constituting the remaining 12%.

The requirements for print quality, sintering density, and mechanical properties of the final parts, along with their industrial feasibility, are the main considerations for selecting a binder. This necessitates a thorough understanding of the printing effects, advantages, and disadvantages of different binders, as well as their applicable scenarios.

Table 2. The difference between in-liquid binding and dry pre-mixed binders.

Types of Binders	Representative Binders	Advantages	Disadvantages	Applicable Printing Scenarios
In-liquid binder	Water-based binders (such as polyvinyl alcohol [42], polyacrylic acid [43], water-based polymer binders [44], and amine-based polymer binders [45]). Solvent-based binders (such as polyvinyl pyrrolidone [46]).	Improve printing accuracy and sintering density [47]; suitable for a wider range of powder materials [40].	Easily clog the nozzle [48].	High-precision, high-density sintering [47]; complex geometric structures; no additional powder pretreatment required [49].
Dry premixed binder	Polymer binders (such as phenolic resin [50] and phenolic polymer binders [51]). Inorganic material-based (such as inorganic colloids [52], etc.).	Lower equipment maintenance costs; improve printing stability [48].	Additional powder processing steps; the uniformity of the binder is difficult to ensure [41].	Filtration materials, high-porosity structures [53]; sand casting, ceramic molds [47]; low-cost, large-scale production.

summarizes the advantages, disadvantages, and applicable scenarios of choosing in-liquid binder spraying versus dry pre-mixing of solid binders.

It is worth mentioning that, in the BJ 3D printing green parts formation process, the printhead is the core of the system, and its performance directly affects the quality of the final product. The printheads in BJ 3D printing equipment are mostly piezoelectric printheads, which control the ejection of droplets by driving deformation of piezoelectric crystals with voltage, as shown in the schematic diagram in Figure 5.

Print resolution and frequency are important indicators of piezoelectric printhead performance, where resolution determines the precision of printed details and frequency affects printing speed and efficiency. Increasing the number of printheads can enhance print quality and speed, but also add complexity to maintenance, especially in high-precision applications, where the failure of any printhead can impact the printing results. Therefore, the selection of printheads must comprehensively consider efficiency and cost to fully leverage the advantages of BJ 3D printing technology.

Table 3. Equipment parameters of mainstream printhead brands.

Company	Model	Number of Nozzles (Units)	Nozzle Size (μm)	Resolution (dpi)	Maximum Frequency (kHz)	Advantage	Disadvantage	Ref.
Xaar (Cambridge, UK)	Xaar 2002	2000	20	720	36	High precision, high reliability, suitable for BJ 3D printing.	Higher cost.	[55]
HP (Palo Alto, CA, USA)	HP Multi Jet Fusion	42,240	20	1200	-	High nozzle density, fast speed, and high print quality.	Complex equipment with high maintenance costs.	[56]
Epson (Suwa, Japan)	PrecisionCore	33,500	20	1440	Variable	High precision and high reliability.	Higher price.	[57]
Toshiba (Tokyo, Japan)	Toshiba TEC CF3	636	22	300	30	High stability, suitable for various applications.	Lower resolution.	[58]
Kyocera (Kyoto, Japan)	SG1024	1024	20	400	20	High reliability, suitable for high-speed printing.	Fewer nozzles, medium resolution.	[59]

summarizes the equipment parameters of mainstream printhead brands.

The aforementioned content elucidates the critical importance of powder particle size, binder mechanism, and nozzle type selection during the green body formation process. For post-processing densification techniques, the LSI process has been successfully implemented in practical SiC component manufacturing. However, variations in green part formation processes among different BJ 3D printing equipment brands not only lead to significantly divergent SiC printing outcomes, but also result in distinct applications of the LSI technique.

Table 4. Differences in the SiC forming process among different brands of BJ 3D printing companies.

Company	Equipment	Characteristics of SiC Component Formation	Applicable Fields	Ref.
Voxelab (Jinhua, China)	Voxelab V1	High-resolution printheads print SiC green bodies with high-precision microporous structures and, combined with LSI, achieve high-precision printing of SiC components.	Small-batch production and SiC components with specific precision requirements (such as in the medical and electronics fields).	[60]
Desktop Metal (Burlington, VT, USA)	Desktop Metal Studio System	Designed to print green bodies with a microporous structure, enabling a fast and efficient sintering process. The combination of multiple printheads and a highly automated system offers significant advantages in fast production and high efficiency.	Industry applications requiring efficient large-scale production (such as in the manufacturing of lightweight automotive parts).	[61]
ExOne (North Huntingdon, PA, USA)	ExOne S-Max	By printing green bodies with up to 50% porosity, it facilitates infiltration with liquid silicon, resulting in SiC components with high density, high strength, and high heat resistance.	High-performance ceramic components (such as gas turbine parts, aircraft engine components, etc.) and industrial components with complex geometries.	[62]
3D Systems (Rock Hill, SC, USA)	ProJet MJP 2500	Utilizes high-speed, high-resolution printheads to rapidly print SiC green bodies with high-precision microporous structures and, combined with LSI, enables rapid prototyping of high-quality components.	Manufacturing of components with high-quality requirements (such as shaft supports, aerospace engines).	[63]

enumerates the BJ 3D printing equipment brands commonly employed for SiC component printing, detailing their respective process characteristics in SiC component formation and summarizing their applicable scope.

2.2. Key Parameters Affecting Formation Quality

In the BJ 3D printing process, monitoring key quality parameters is essential to ensure that SiC printed parts meet expected standards in functionality, appearance, and durability, especially in industrial and high-precision manufacturing fields. By monitoring these parameters in real-time, deviations between the final parts and the design model can be visually presented, avoiding errors in shape or size and ensuring that the product meets the specified functional requirements.

To meet the demands of the high-precision manufacturing market, qualified SiC BJ 3D printed parts must not only possess high printing quality, but also have sufficient mechanical strength to adapt to different application environments. However, insufficient precision during the printing process (including shape accuracy, dimensional accuracy, and surface roughness) often leads to additional post-processing steps, such as machine grinding [64], polishing, surface melting [65], and robotic finishing [66]. These extend the manufacturing cycle and limit the advantages of BJ 3D printing technology and its widespread application in ceramic component production. As mentioned earlier, printing resolution directly affects the upper limit of printing accuracy, and higher resolution helps improve the dimensional and shape accuracy of the components. Upgrading the hardware of the printing equipment (such as the printhead or the number of printheads) can effectively enhance the overall resolution of the printing system, thereby improving printing accuracy. Additionally, the porosity of the powder bed is also a key factor affecting accuracy. Uniform porosity in the powder bed can prevent uneven penetration of the binder, leading to leakage of SiC powder outside the component profile and resulting in dimensional errors. By selecting the appropriate powder particle size and shape and optimizing the powder spreading process (such as the structure, rotation speed, and direction of the rotating roller), a smooth and uniform powder bed can be formed, thereby improving the dimensional accuracy of the printed parts.

On the other hand, the strength of the components directly affects their durability and reliability during use. High-strength SiC components can withstand greater forces and stresses, preventing deformation, cracking, or failure, thus extending their service life. The strength of the final components is predominantly determined by densification processes during post-treatment (e.g., sintering, LSI, etc.) of the green parts, yet the state of the printed powder bed equally exerts a non-negligible influence on the ultimate component quality. A uniform and dense powder bed typically indicates more homogeneous pore distribution and material arrangement within the green parts. Green parts with non-uniform porosity may induce a series of critical issues affecting final component quality during post-densification, such as preferential shrinkage in high-porosity regions generating internal stresses and dimensional deformations during sintering or selective melt infiltration leading to incomplete reactions and consequent fluctuations in Si/SiC content in the final components during LSI. Therefore, precise regulation of the powder bed state constitutes an indispensable aspect for enhancing final component quality. Additionally, the high chemical inertness and thermal stability of SiC materials make the choice of binder crucial. Differences in bonding performance between the binder and SiC powder can affect the density during the sintering process, which in turn influences the strength of the formed components. However, adding the curing agent to the powder bed in advance may cause premature reactions or moisture absorption in the powder, affecting the quality of the powder bed and printing accuracy. Therefore, developing binders that react directly with SiC is key to solving such issues.

While macroscopic mechanical properties provide a comprehensive assessment of material strength and offer a general indication of internal defects, they are insufficient to reveal the critical microscopic mechanisms that govern long-term material reliability. Internal defect detection enables the identification of early-stage damage that cannot be captured through macroscopic mechanical testing-damage which, in high-precision applications, may originate from micron-scale flaws and lead to premature component failure—thus significantly reducing safety risks. Internal defects (such as voids, cracks, and regions of incomplete fusion) significantly affect the long-term performance of the material. Internal defects may lead to stress concentration, reducing the material’s fatigue life and impact resistance, and even causing brittle fracture or premature failure under dynamic or complex loads. Furthermore, internal defects may further propagate under environmental conditions such as repeated loading, thermal cycling, or corrosion, ultimately leading to premature material failure. Therefore, detection of internal defects is crucial for studying the failure mechanisms of components and predicting their service life, while also providing important feedback for process optimization and formation quality control.

When 3D printed objects with poor mechanical properties are applied in practical fields, many potential issues may arise. For example, parts with insufficient strength may easily break or undergo plastic deformation when subjected to external forces, especially in high-load or high-stress environments. This situation may lead to component failure, affecting overall structural stability and safety. Parts with poor hardness are prone to wear during friction or long-term use, especially when used as wear components (such as gears, bearings, etc.), greatly reducing their durability and service life. Parts with poor impact resistance are prone to brittle fracture under sudden impacts or high loads, creating safety hazards. To avoid potential problems caused by poor mechanical properties, optimizing the printing process to obtain high-quality green bodies is the foundation for enhancing the mechanical strength of printed parts. Additionally, improving quality inspection techniques for green bodies and enhancing the density and strength of materials through post-processing techniques (such as heat treatment, sintering, or adding composite materials) for lower-quality green bodies are important. Finally, it is key to specifically enhance the relevant mechanical strength according to the application area of the printed parts to minimize the occurrence of potential issues. For example, printed parts used in high-frequency vibrations or impact load applications can choose binders with better adhesiveness, or reinforcing materials with higher toughness can be added to improve impact resistance.

In summary, utilizing key quality parameters to monitor the formation quality of SiC 3D-printed parts is a focus of current research in BJ 3D printing technology. Through effective parameter monitoring and process improvements, the precision and strength of components can be enhanced, promoting widespread application of this technology in industrial and high-precision manufacturing.

3. Quality Control of Silicon Carbide Printed Part Formation

This chapter thoroughly investigates the critical factors influencing the final quality of SiC components throughout BJ 3D printing and their corresponding control strategies. Firstly, we examine the key challenges and solutions affecting the formation quality of SiC green parts based on a literature review, including nozzle clogging issues, acquisition of uniform and dense powder beds, and improvement of stair-stepping effects. Secondly, we comprehensively summarize the current application status and optimization strategies of various post-densification processes. Finally, special attention is given to the advanced quality inspection and characterization techniques currently employed in BJ 3D printing.

3.1. The Impact and Control of Key Printing Parameters on Green Part Formation Quality

The fabrication of green parts serves as a pivotal stage in binder jetting 3D printing, critically determining the surface accuracy of the final components. Nevertheless, the printing of SiC green bodies still encounters multiple challenges that adversely affect formation quality. This section provides a systematic examination of parameter interactions, while reviewing documented solutions in the literature, with a particular focus on surface accuracy issues, including nozzle clogging, acquisition of uniform and dense powder beds, and stair-step effects on green part surfaces.

3.1.1. Nozzle-Clogging Issues

During the printing process, clogging of the printhead nozzle can cause the binder to migrate outside the intended geometry, resulting in a phenomenon known as “feathering”, which decreases the accuracy of the printed parts and is regarded as one of the main sources of shape accuracy issues. Figure 6 illustrates the impact of nozzle clogging on printed parts.

Controlling the viscosity and surface tension of the binder to prevent the formation of satellite droplets [69] or to delay nozzle drying [49] is a common method for addressing nozzle clogging. Normally, droplets fall in a tadpole shape with a tail. Due to the effects of surface tension, the trailing liquid breaks off to form small droplets that trail behind the main droplet, creating a tail-like structure known as a satellite droplet. Figure 7a systematically illustrates the key stages and parameter relationships during droplet formation and satellite droplet generation in the inkjet process, where Γ represents the aspect ratio of the tail at the exit pinch-off, V_j denotes the mean jetting velocity of the ink, L_p corresponds to the total length of the ligament during exit pinch-off, and t₂ and t₁ indicate the exit pinch-off time and the initial ink ejection time from the nozzle orifice in each droplet formation cycle, respectively. The right panel of Figure 7a clearly labels the separated states of the primary droplet and satellite droplet, visually demonstrating how tail breakup leads to satellite droplet formation. Figure 7b1–b6 vividly demonstrates the jetting states during droplet formation through comparative illustrations, including no droplet formation, single droplet formation, single satellite droplet formation, and multiple satellite droplet formation.

Researchers such as Henderson [71] and Zhang Y [72] have provided a detailed explanation of the causes of nozzle clogging due to satellite droplets. In this regard, Zhao K [67] noted that a distance of 1–3 mm must be maintained between the printhead and the powder bed to ensure that satellite droplets have enough time to merge with the main droplets. Moreover, some smaller satellite droplets may be blown away from the jet axis by lateral airflow and evaporate. When the solvent evaporates and these smaller satellite droplets are suspended in the air as aerosols, they may contribute to “nozzle clogging”. To better describe the fluid properties of binders, guide the selection or preparation of binders, and regulate binder droplet behavior, parameters such as Reynolds number (Re), Weber number (We), and Ohnesorge number (Oh) are commonly used to measure the liquid properties of binders [73]. These three parameters are related to fluid density, fluid dynamic viscosity, fluid surface tension, droplet velocity, and characteristic length. Fromm et al. [74] first proposed the Ohnesorge-related parameter Z = 1/Oh to characterize the printability of binders, which is correlated with the binder’s dynamic viscosity, surface tension, fluid density, and characteristic length. Experimental investigations by Reis et al. [75] on the regulation of parameter Z ranges demonstrated that, when Z < 1, the viscous forces of the binder become dominant. This indicates that, under jetting pressure, high viscous dissipation prevents droplet ejection and significantly increases the likelihood of nozzle clogging. Conversely, when Z > 10, insufficient viscous forces result in continuous jetting phenomena, leading to satellite droplet formation behind the primary droplet, which may cause nozzle clogging or reduced resolution on the powder bed surface. Consequently, binders are considered unsuitable for printing when the Z parameter falls within either of these two ranges.

3.1.2. Uniform and Dense Powder Bed

Binder deposition within the powder bed represents the most fundamental process in binder jetting 3D printing, governing selective powder bonding and layer-wise fabrication. A powder bed with homogeneous porosity distribution is a prerequisite for precise binder deposition within predefined geometries. As shown in Figure 8, in powder beds with heterogeneous pore distribution, the deposited binder preferentially infiltrates regions with smaller pores, potentially bonding unintended powder particles at structural boundaries and consequently increasing the surface roughness of green components. On the other hand, the cavities formed within the powder bed may hinder the interlayer adhesion from overcoming shear forces, which can easily lead to layer misalignment (this phenomenon is referred to as “shearing/shifting”) [76]. This results in significant deviations of the printed layers from their intended positions, thereby reducing the dimensional accuracy of the green parts [77]. Furthermore, the non-uniform porosity caused by these cavities can lead to uneven density distribution in the green body, ultimately causing fractures or deformations in the formed printed parts during the subsequent sintering process.

Therefore, constructing a homogeneous and dense powder bed represents a fundamental prerequisite for manufacturing high-precision green bodies. To achieve optimal powder bed uniformity and densification in additive manufacturing processes, it is essential to systematically investigate the governing mechanisms that influence powder packing quality. Key factors requiring particular attention include the detrimental effects of binder–powder interactions on bed homogeneity, the agglomeration behavior and flowability challenges associated with fine powders, and the critical powder spreading dynamics during the deposition process.

• Binder–powder interaction behavior

The binder–powder contact tunneling model proposed by Emady H N [79] vividly demonstrates how binder impact on the powder bed induces distinct particle motion patterns. Figure 9a illustrates incomplete penetration of binder droplets into a loosely packed powder bed, forming dry aggregates and causing surface collapse defects that lead to non-uniform porosity in subsequently spread powder layers. Figure 9c displays the crater effect resulting from high-speed binder droplet impact on a homogeneous powder bed, where droplets spread along crater walls while entraining particles during retraction, ultimately forming more spherical binder particles that penetrate the powder bed. This crater-induced powder splashing is recognized as a primary source of surface roughness, as both the craters and splashed powder compromise current layer accuracy while adversely affecting subsequent layer spreading. Figure 9b demonstrates the desired impact mechanism: under conditions of dense and uniform powder packing, low-speed impacts result in droplet spreading into flattened discs that penetrate downward with minimal surface defects. The universal approach for achieving powder beds with uniform porosity involves adjusting binder parameters to mitigate crater-induced splashing [80], with key control parameters including binder volume, initial velocity, and viscosity [81].

In addition to adjusting binder parameters, the hydrophilicity of the powder material and the selection of binder type also significantly influence the impact of binder–powder interactions on the powder bed state. Hydrophilic powders tend to adsorb more binder, forming a uniform wetting layer that promotes bonding between powder particles. However, excessive hydrophilicity may cause over-adsorption of the binder during the printing process, leading to insufficient flowability or excessive expansion, which can result in uneven powder spreading and defects in the new powder layers. In contrast, hydrophobic powders have a weaker ability to adsorb binder, and the binder’s penetration capability in the powder layers is poor, resulting in weak bonding between layers. Additionally, binder droplets that remain too long in the powder layer may form “balling defects” [83]. Therefore, to reduce surface defects in the powder layer caused by binder–powder interaction, it is necessary to develop appropriate control strategies based on the hydrophilicity of the powder. For example, when using hydrophilic powders, water-based binders containing more hydrophilic groups can be selected [31], while for hydrophobic powders, organic binders with stronger hydrophobic properties can be chosen. Alternatively, surface pretreatment of the powder (such as acid washing or modified coatings [84]) can improve its hydrophilicity, thereby optimizing the interaction with the binder and improving print quality.

b.

Powder agglomeration and spreading defects

Research indicates that the particle size of the powder is closely related to the resolution of the formed products [85]. Although traditional equipment can form larger-particle powders (>200 μm), the application of fine and ultrafine powders (≤120 μm) is more common in practice to avoid secondary processing of high-strength SiC products and to meet the urgent demand for high-precision, high-quality complex structural SiC ceramic materials in critical fields such as national defense and industry. However, finer powders do not necessarily lead to better printing outcomes. Excessively fine powders may cause flowability issues that affect printing accuracy. Research has shown that fine powders have low flowability, making it difficult to achieve uniform spreading, which can create pores during the printing process and adversely impact structural density and dimensional accuracy [86]. Castellanos [87] defined the concept of the number of viscous particle bonds, categorizing powders into viscous and non-viscous types. This classification helps explain the phenomenon that, as particle size decreases, the number of viscous particle bonds increases, leading to a higher tendency for powder agglomeration, which results in poor powder flowability [88]. This cohesive powder tends to form agglomerates within the powder bed, which can induce defects and heterogeneous pore structures, consequently compromising the uniformity and compactness of the powder bed. Therefore, improving the flowability of fine SiC powders to minimize particle agglomeration during spreading represents a critical measure for achieving uniform and dense powder beds.

Research on non-cohesive non-spherical powders indicates that the ratio of bulk density to tapped density decreases with increasing sphericity [89]. Powders with a Hausner ratio of less than or equal to 1.25 are considered freely flowing, while the Hausner ratio of cohesive and non-flowing powders exceeds 1.40 [87], which indicates that, the closer the shape of the powder particles approaches sphericity, the better the flowability of the powder. Based on this theory, researchers including Igor Polozov [45] developed SiC fiber-reinforced SiC composites using BJ AM combined with a polymer infiltration and pyrolysis process. Spherical SiC powders were prepared using ball milling, spray drying, and thermal plasma treatment. Characterization of the powders shows that, compared to irregularly shaped SiC powders, the use of spherical SiC powders results in higher fracture toughness and hardness. Additionally, some researchers argue that using nanoparticles as flow agents to enhance the flowability of SiC powders offers greater advantages compared to the cost and technical challenges involved in the preparation of spherical SiC particles. Amanov et al. [84] examined improvement of the mechanical and tribological properties of SiC produced by AM using ultrasonic nanocrystal surface modification (UNSM) at 23 °C (room temperature, RT) and 900 °C (high temperature, HT). The results indicate that, after UNSM treatment, the surface roughness of the printed SiC samples showed a decreasing trend at both temperatures. This type of surface coating can enhance the flowability, uniformity, and handling properties of the powder, making it easier to process and use [90]. On the other hand, research has been proposed on mixing multimodal powders during the pretreatment process to improve powder bed density. For monomodal powders, wider particle size distribution leads to higher packing density of the powder bed. Liu et al. [91] experimentally compared the powder bed density of two types of 316 L stainless steel powders with similar average particle sizes but different widths of particle size distribution. The comparison results showed that powders with a wider particle size distribution achieved higher powder bed densities. In a wider distribution, smaller powder particles at the lower end of the particle size range can fill the voids of larger particles at the upper end, resulting in improved powder bed density and uniformity.

Thus, to address the issue of poor spreadability of fine SiC powders during the binder jetting printing process, preparing multimodal SiC powders by mixing powders of different sizes is an important method to improve the flowability of the powder bed, which enhances the strength and surface quality of the green bodies. The preparation of bimodal powders is illustrated in Figure 10.

However, to achieve the aforementioned improvements in performance, it is essential to consider factors related to the powders when preparing bimodal powders [92,93,94]. It is worth noting that the use of multimodal powders may also negatively affect powder bed density. Research by Du et al. [92] indicates that mixing 10 μm and 2 μm alumina powders reduces powder bed density. This may be attributed to segregation phenomena among the particles, leading to separation or agglomeration of the powder particles during the mixing process. Therefore, while using multimodal powders or powders with a broad distribution can enhance powder bed density, it is also important to consider the impact of particle segregation on powder bed quality. Introducing external stimuli during the powder spreading process (such as mechanical vibration [95], sound waves [96], and magnetic stirring [97]) can improve the flowability and packing density of SiC powders to varying degrees. However, additional processing steps and units, along with high operational costs, are inevitable. In contrast, preparation and processing of SiC during the pretreatment process represent a more economical and efficient method for improving print quality, attracting significant attention from numerous researchers regarding its research value and prospects.

c.

Fine powder spreading process

In addition to the aforementioned modification and pretreatment processes for SiC fine powder, the powder spreading process can also contribute to the fabrication of uniform and dense powder beds. In binder jetting 3D printing, the spreaders evenly distribute SiC powder from the powder reservoir to the printing chamber, enabling subsequent printing operations. The rational design and selection of the spreaders are crucial for obtaining uniform and compact powder layers. Powder spreaders can be classified into two main types: wipers and rollers.

Regarding wipers, different wiper profiles demonstrate distinct powder spreading performance. In the study by Haeri et al. [98], the wiper profile was governed by the following equation:

$${\left|{\displaystyle \frac{y_s}{a_s}}\right|}^{n_s}+{\left|{\displaystyle \frac{z}{b_s}}\right|}^{n_s}=1$$

(1)

By adjusting these parameters (a_s, b_s, and n_s), various wiper profiles were obtained, as illustrated in Figure 11. D_sph represents the sphere diameter (for rods), with a value of 10⁻⁴. The parameter a_s denotes the spreader profile thickness parameter, ranging from 10 to 25 or 100 D_sph. The parameter b_s indicates the spreader profile height parameter, with a range of 10 to 20 or 50 D_sph. The shape parameter n_s, which determines the profile geometry, varies among 0.5, 1.0, 1.5, 2.0, and 5.0. Here, x and z correspond to the coordinates of the wiper along the spreading and building directions, respectively. Their simulation results revealed that the powder bed density reached its maximum value at n_s = 5 across different a_s and b_s combinations [98].

On the other hand, extensive studies have demonstrated that rollers, when employed as powder spreaders, can achieve higher powder bed densities compared to wipers [99,100,101,102,103]. However, it should be noted that the rotation direction of rollers may affect powder bed surface integrity. Based on their rotational orientation, rollers can be classified into two types: forward-rotating rollers (as shown in Figure 12a) and counter-rotating rollers (as illustrated in Figure 12b).

Forward-rotating rollers exerts significant shear force [105] and compressive force [106], allowing for higher compaction density when passing over the powder bed. However, the fine SiC powder used in the printing process has a high viscosity, and the large compressive force can cause the cohesive particles to adhere more readily to the rotating roller, forming powder clumps, which results in the formation of pits on the surface of the powder bed and leaves new “craters” in other areas of the powder layer, severely affecting the surface accuracy of the printed parts. To mitigate or prevent such surface defects caused by the substantial compaction force of forward-rotating rollers on the powder bed, reducing the powder quantity ahead of the forward-rotating rollers proves effective [106]. This can be implemented by incorporating a pre-spreading step using either a wiper or counter-rotating roller prior to final spreading with forward-rotating rollers [102,107]. The pre-spreading and final spreading procedures can be executed either through separate traverses or within a single traverse operation. However, this approach inevitably compromises printing efficiency and increases process costs. In comparison, backward-rotating rollers are more beneficial for the movement of powder particles in the BJ 3D printing of SiC materials. Nan et al. [108] conducted a simulation study on the powder spreading effects of backward-rotating rollers, which indicated that, during the passage of the backward-rotating roller over the powder bed, some particles are lifted by the rotating roller and enter the powder bed, subsequently circulating in the stacking area. This allows particles more time to rearrange, which reduces the occurrence of powder agglomeration and achieves a higher and more uniform powder bed density. Moreover, rollers with larger diameters and smoother surfaces can achieve higher powder bed densities [109,110]. Therefore, the counter-rotating roller is most commonly used for powder spreading.

Finally, when employing a roller for powder spreading, the influence of the roller’s lateral speed must also be taken into consideration. Earlier research by Seluga et al. [111] concluded that, when the lateral speed does not exceed 12 mm/s, the packing density of the powder bed increases slightly with the increase in lateral speed. However, with iterative advancements in powder binder 3D printing technology, when the experimental range for the lateral speed of the powder spreader is expanded to 0–300 mm/s, the impact of the lateral speed of the rotating roller on the spreading quality needs to be redefined. Current research generally indicates that increasing the lateral speed of the rotating roller will decrease the density of the powder bed, and, as the translational speed of the rotating roller increases, the surface roughness monotonically increases, while the surface quality of the powder layer deteriorates with the increase in spreading speed [101,110,112,113,114,115]. Understanding the underlying principles is crucial for precise control of the printing process. The theories of “backflow” and “powder splashing” can be used to explain this variation. When the scanning speed is high, the particles deposited on the powder bed can continue to flow for a distance due to their significant momentum. This backflow phenomenon results in uneven or even discontinuous layers on the surface [116].

3.1.3. Elimination of the Stair-Step Effect

The step-like surface defects formed on green bodies due to the layer-by-layer deposition characteristics of binder jetting 3D printing are defined as the “stair-step effect” (as shown in Figure 13). The “stair-step effect” is considered an unavoidable systematic error in powder binder 3D printing. Theoretically, if the layer thickness in slicing approaches the infinitesimal, the edge profile of the model in the slicing software will coincide with the edge profile of the actual printed object, thereby completely eliminating the stair-step effect. However, it is important to note that the layer thickness should not be less than the maximum particle size of the powder [34] to meet the basic requirements for powder spreading and printing resolution.

Figure 14 vividly illustrates the impact of the stair-step effect on the surface accuracy of thin-layer slicing versus thick-layer slicing. In actual printing, appropriately reducing powder layer thickness is a common practice to suppress the “stair-step effect”. As summarized by Chen [118], the selection of layer thickness is one of the main factors affecting the surface roughness of powder binder 3D printing technology, and the stair-step effect exhibits a proportional relationship with powder layer thickness. However, on the other hand, reducing the slicing layer thickness results in an increase in the corresponding printing time, which significantly decreases printing efficiency. Although using multiple printheads can help reduce printing time, this solution may be prohibitively expensive [119].

The adaptive slicing process is proposed based on this issue, by establishing a relationship between stair-step error and model parameters to determine the thickness of layering based on the magnitude of the stair-step error for thin or thick layers at specific locations. Thin layers are applied in areas where stair-step errors are more likely to occur to ensure printing accuracy, while thicker layers are implemented in areas less likely to cause stair-step errors to increase printing speed. After Dolenc et al. [121] developed an algorithm to address the stair-step effect by controlling the height of peaks within the tolerance range of the surface, and Kulkarni et al. [122] developed an algorithm using surface parameters to determine variable thickness, the literature on adaptive slicing technology has attracted the interest of many scholars and has begun to be widely researched. For example, the adaptive algorithm developed by Ma et al. [123] is more suitable for parts with curved surfaces. Their algorithm directly applies to Non-Uniform Rational B-Spline (NURBS) surface models, allowing them to achieve precise and smooth part surfaces while employing a selectively hatched strategy to reduce build time. For instance, Ratnadeep Paul et al. [124] define the degree of the stair-step effect using the angle A_stair between the build direction of the outer surface of the CAD (Computer Aided Design) model of the printed layer and the slicing plane. As the A_stair angle increases, the error area significantly increases. By controlling the layer height and the A_stair angle, the printed part’s boundary can be precisely matched with that of the CAD model, which reduces the differences between the printed pattern and the CAD model, thereby minimizing the impact of the stair-step effect; thus, Ratnadeep Paul’s algorithm is more versatile. For example, Zhou et al. [125] utilized the OpenGL graphics library (OpenGL 1.3) to visualize solid models. This approach allows users to specify the permissible cusp height based on different tolerance requirements, thereby enabling adaptive slicing and improving the surface finish of printed parts. Their algorithm allows the slicing process to be independent of specific CAD modeling software. Research and development regarding adaptive slicing algorithms have expanded the slicing process for handling complex-shaped printed models, but currently, adaptive slicing strategies are still largely in the research interest phase and are seldom implemented on BJ 3D printers. The high research and development costs are considered the main reason for the lack of widespread adoption of adaptive slicing. However, from the essence of the BJ 3D printing process of green body formation, Bas et al. [126] proposed a new perspective, that spraying the same volume of binder on layers of different thicknesses will inevitably lead to accuracy issues in the printed parts. As shown in Figure 15, the bonding and reactions between binder droplets and the powder or substances within the powder are crucial for the binder green body. Insufficient binder spray volume can lead to inadequate adhesion between layers (as shown in Figure 15c), while excessive binder spray volume can result in unnecessary powder bonding, causing shape accuracy issues (as shown in Figure 15a).

Thus, it is crucial to apply a suitable amount binder during the printing process (as shown in Figure 15b). As demonstrated in the research report by Patirupanusara et al. [127] on the effects of binder content on the formability and performance of polymethyl methacrylate (PMMA), it is necessary for the binder content to be greater than 10% when 3D printing parts from PMMA. When the binder content exceeds 40%, it is prone to causing shape deformation. This indicates that excessive binder can lead to over-spreading, resulting in reduced surface smoothness and poor dimensional accuracy, and the bonding of previous layers may also be affected by the excess binder. Taturation of the binder is used to describe the percentage of fluid-filled pores when the binder permeates downward into the powder bed [128]. Currently, the saturation of the binder is used to measure the volume content of the binder. Undersaturation (<1) indicates that the powder pores are not fully filled, which highlights the concern of insufficient bonding leading to the “layer shifting” phenomenon, as well as the potential for high levels of voids and porosity that may occur after the burnout and sintering steps. In contrast, oversaturation (>1) indicates that the powder pores are filled with binder, and that there is a phenomenon of binder overflow, which is likely to cause additional powder particles to adhere to the surface of the 3D-printed parts, leading to increased surface roughness and dimensional errors [118,129]. The lack of adaptive binder control strategies for different adaptive layer thicknesses is a significant factor affecting the effectiveness of adaptive algorithms in controlling print quality, and it is also a major obstacle to their application in practical printing processes. Wijshoff H, in his latest review on droplet jetting research [130], pointed out that the key to controlling forming accuracy is how to eject droplets of any volume. He further clarified the main issue that current research should focus on, which is to study the relationship between binder spray volume and formation accuracy based on the fundamental principles of micro-droplet jetting. Starting from the fundamental principles of micro-droplet jetting, research should examine the relationship between binder spray volume and formation accuracy at specific layer thicknesses. Liu et al. [54] established a mechanical model of the MDI device’s mechanical actuator based on the droplet generation process model at the printhead developed by Pucci [131] and Dong [132], which considers the effect of the structural displacement field. They analyzed the relationship between the characteristics of the MDI device and the inherent structural parameters and established an equivalent model between the displacement field and the electric field, substituting the electric field for the displacement field. By establishing the relationship between the excitation pulse parameters and droplet volume, the piezoelectric printhead is driven to accurately eject predetermined binder droplets. To enhance the formation accuracy of precision casting sand molds, in Liu’s latest research [133], he employed a precise ink droplet control process to drive the printhead to eject droplets of accurate volume and conducted a preliminary analysis of the penetration and diffusion phenomena of binder spray volume within the sand powder layers (as shown in Figure 16). In this study, the spreading area of droplets on the powder bed was determined using a machine vision system coupled with a high-resolution camera, while the penetration depth was measured by cross-sectional analysis with a profilometer. Liu [133] believes that the motion between the powder and the binder is a complex coupling relationship, and that this relationship can vary significantly due to differences in powder materials and binder types.

This study provides important guidance for the control of layer thickness and binder spray volume to improve formation quality in form printing, and it offers empirical guidelines for the adaptive allocation of binder spray volume at different layer thicknesses within adaptive slicing strategies. Currently, BJ 3D printing technology in SiC material formation is in its infancy, and the relationship of the binder within the SiC powder bed is still unclear. In light of the aforementioned research perspectives, studying the deposition patterns of binder in SiC powder beds is urgently needed. To improve the formation quality of BJ 3D printing in the field of SiC manufacturing, related studies on deposition experiments must provide more scientific and precise guidance for process control. As mentioned at the beginning of this section, conducting more in-depth and detailed studies on the effects of various printing parameters on BJ 3D print quality, in conjunction with conventional BJ formation processes, and innovating based on the unique material properties of SiC powder are key to enhancing the formation quality of binder 3D printing of SiC materials.

3.2. Densification Post-Processing Techniques

After the completion of binder jetting 3D printing, the strength of the SiC green body primarily relies on the binder’s bonding effect, rather than direct interparticle connections among the powder particles. Additionally, since the binder only partially fills the voids between the particles, the green body typically exhibits high porosity. Consequently, additional post-processing steps are required to densify the SiC green body, enhancing its density and mechanical properties to meet practical application requirements.

To address the powder spreading challenges inherent in fine particulate systems, the predominant approach in BJ 3D printing manufacturing currently favors the utilization of relatively coarser SiC particles. This methodology, however, presents a fundamental conflict with the thermodynamic requirements for achieving effective post-printing densification at conventional sintering temperatures. While significant advancements have been made in optimizing particle packing behavior through controlled powder characteristics and precisely tuned printing parameters [134], the resultant green bodies persistently demonstrate spatial heterogeneity in their microstructural architecture. Furthermore, the intrinsic material properties of SiC, particularly its exceptionally high melting point, necessitate the implementation of extreme thermal processing conditions, typically exceeding 1800 °C, to accomplish adequate densification of SiC green bodies [135,136,137]. Such high-temperature sintering not only places extremely demanding requirements on equipment, but may also lead to deformation and cracking of the highly porous SiC green bodies. In contrast to conventional sintering, processes including liquid silicon infiltration (LSI), chemical vapor infiltration (CVI), and polymer impregnation and pyrolysis (PIP) can uniformly infiltrate porous preforms to achieve homogeneous densification. This characteristic aligns well with the capability of BJ 3D printing to fabricate green bodies with high porosity (approximately 50%) [138], and these techniques have been increasingly applied in the post-processing densification of complex-shaped SiC components manufactured by BJ technology. The specific details of these three post-processing techniques are presented in

Table 5. General overview of the LSI, CVI, and PIP processes.

Process Name	Process Principle	Advantages	Disadvantages	Theoretical Densification Rate	Ref.
LSI	The porous SiC-C preform is immersed in molten silicon, and the liquid silicon infiltrates into the pores through capillary action, reacting with carbon to form SiC that fills the pores, thereby achieving densification.	High densification efficiency, simple process, suitable for large-scale production.	Residual silicon is difficult to completely remove.	Approximately 95%	[139,140,141,142,143]
CVI	The gaseous precursor enters the reaction chamber and decomposes within the pores of the porous SiC preform, depositing SiC through multiple infiltration and deposition cycles to gradually fill the pores and achieve densification.	Capable of producing high-purity SiC; minimal risk of material deformation.	The process exhibits extended cycle duration, necessitates complex equipment with elevated capital and maintenance expenditures, and demonstrates suboptimal vapor-phase infiltration efficiency.	Approximately 90–92%	[144,145]
PIP	The preform is immersed in a silicon-based polymer precursor, and, under an inert atmosphere at appropriate temperatures, the polymer undergoes pyrolysis to generate SiC that fills the pores. Multiple impregnation and pyrolysis cycles are required until the desired density is achieved.	Low pyrolysis temperature; enables production of high-purity SiC components; relatively simple process.	The process has a long cycle time, and polymer shrinkage during pyrolysis poses a risk of material cracking.	Approximately 85–95%	[23,45,146]

.

Although the aforementioned post-processing techniques have achieved corresponding results in the densification of SiC green parts manufactured by BJ 3D printing technology, the limitations of existing post-processing methods and the challenges associated with complex geometries and large-scale production continue to drive extensive research efforts among scholars.

Current research trends in post-processing densification of SiC components focus on developing optimization approaches to address existing process limitations or synergistically combining multiple post-processing techniques to enhance efficiency and overcome current densification constraints. For the LSI process specifically, the primary challenge lies in minimizing silicon residue within SiC components, as residual silicon significantly degrades high-temperature performance, mechanical properties, and oxidation resistance. Consequently, porous binder jet 3D-printed SiC preforms must contain sufficient carbon content to achieve complete reaction with silicon. The phenolic binder employed in BJ 3D printing can provide a certain amount of carbon (approximately 2–3% [147]) to the printed product. However, this carbon content is insufficient to react with approximately 50% of infiltrated silicon. Therefore, carbonization of the porous SiC green body prior to LSI is essential. Common carbonization methods include using carbon powder instead of SiC powder for printing [148,149], incorporating carbon-containing mixtures into SiC printing powder [150,151], and applying phenolic polymer impregnation and pyrolysis [152,153,154]. However, the aforementioned carbonization methods lack precise carbon content regulation, where excessive carbon may clog pores and impede the smooth infiltration of molten silicon during LSI. As demonstrated in the report by Corson L et al. [12] on composites fabricated through multiple phenolic resin impregnation–pyrolysis cycles followed by final silicon reactive melt infiltration, optimal values of density, Young’s modulus, flexural strength, and thermal conductivity were achieved after two impregnation–pyrolysis cycles. Beyond two cycles, diminishing returns were observed due to pore blockage by excess carbon, resulting in reaction obstruction that generated residual porosity along with unreacted carbon and residual silicon.

Therefore, ensuring equilibrium between carbon content and the reaction with liquid silicon in the carburization process while minimizing the residual silicon content as much as possible is a critical challenge that needs to be addressed in the LSI process. Lv et al. [155] utilized high-specific-surface-area porous carbon to construct an optimized silicon infiltration channel, significantly enhancing the C-Si reaction and reducing the residual silicon content to 5.2 vol%. However, the study did not report the residual carbon content. A. Fleisher et al. [147] designed a phenolic resin binder impregnation (PRBI) process, where each PRBI and pyrolysis cycle contributed approximately 3% carbon, as shown in Figure 17a. With increasing numbers of PRBI cycles, the deposited carbon progressively fills the pores, resulting in significant density enhancement of the printed “green” samples (as evidenced in Figure 17b). This clearly demonstrates the remarkable carbon-supplying capability of repeated PRBI treatments for SiC green bodies. The residual liquid silicon content in SiC green bodies exhibited a significant decrease with an increasing number of PRBI carbonization treatments prior to chemical liquid silicon infiltration (CLSI), as clearly demonstrated in Figure 17c. This phenomenon can be mechanistically explained by the significantly increased carbon content within the pores of SiC green bodies following multiple PRBI treatments. During the subsequent CLSI process, this excess carbon chemically reacts with molten silicon to form additional SiC, which consequently reduces the residual silicon content in the resulting SiC samples. Their experimental results indicated that additional PRBI cycles (beyond three) could lead to pore blockage, thereby hindering CLSI and increasing the residual silicon content.

To prevent excessive PRBI cycles from resulting in residual liquid silicon, they limited the PRBI cycles to three, obtaining half of the required carbon content. The remaining carbon was introduced by mixing additional carbon sources into the initial powder before printing. Their experimental results demonstrated that this additional carbonization method could significantly reduce the residual silicon content to as low as 15% or even lower, offering a new approach to addressing the issue of residual silicon in the LSI process. It is worth noting that, in the study by Fleisher et al. [147], mechanical properties were not reported. Building upon this research, Feng et al. [17] further conducted a comprehensive study on the effects of PRBI cycle count and printing layer thickness on formation accuracy, silicon content, and mechanical properties. Their findings indicated that, with a layer thickness of 0.15 mm—where green body compression performance and dimensional accuracy were optimal—samples subjected to LSI treatment with two PRBI cycles exhibited the highest flexural strength (257 ± 14.26 MPa) and the lowest residual silicon content, estimated at 10.2 vol% based on SEM images and 12.23 vol% based on XRD analysis.

Secondly, for the PIP process, the prevalent issues of cracks and excessive open porosity in the processed SiC materials remain significant challenges. Studies on the effects of PIP cycles on the density and pore structure development of binder jetting-printed SiC have shown that the residual porosity in PIP samples originates from several factors. These include localized cracking during pyrolysis due to volume shrinkage of polymer precursors in highly infiltrated regions, as well as the formation of large internal cracks caused by gas accumulation and increased pressure during pyrolysis [156]. Wang et al. [24] mitigated regions with low particle packing density and large open pores by controlling the printing layer thickness (set at 50 μm), thereby reducing the occurrence of cracking due to polymer precursor volume shrinkage during pyrolysis. After seven PIP cycles, they obtained SiC ceramics with a strength of 228.7 ± 14.2 MPa. Their study highlighted that additional low-temperature curing and impregnation before pyrolysis could significantly improve yield and density after the first PIP cycle. With only three PIP cycles, they achieved a room-temperature flexural strength of 66.8 ± 2.5 MPa and a Young’s modulus of 69.5 ± 2.8 GPa, enhancing the efficiency of the PIP process.

The above optimizations focus on the process parameters of PIP. On the other hand, researchers have been developing superior polymer-derived SiC precursors to mitigate gas accumulation during pyrolysis, thereby reducing internal cracking in PIP samples. Compared to the commonly used SiC-based precursor—polycarbosilane (PCS)—innovations in novel SiC-based PIP process precursors are summarized in

Table 6. Precursors for the PIP process in SiC-based component fabrication.

Precursor Polymer for the SiC Matrix	Description of the Precursor	The Prepared Ceramic Material	Number of PIP Cycles	Densification Effect	Ref.
Hyperbranched polymer (mPMS)	Modified by adding 12 wt% crosslinking agent to polymethylsilane (PMS)	α-SiC/β-SiC	10	The material density is 2.5 ± 0.05 g/cm3, reaching 90 ± 2% of the theoretical density.	[157]
Liquid polycarbosilane with active Si–H and 3CHaCH2 groups (LPVCS)	Prepared by using 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (V4) as the curing agent and liquid polycarbosilane as the starting material	SiC fiber-reinforced SiC matrix composites (SiC/SiC)	10	The material density is 2.16 g/cm3, with a porosity of 6.7%.	[158]
Polycarbosilane (PCS) modified with divinylbenzene (DVB)	Modify the conventional polycarbosilane (PCS) precursor with 20% of divinylbenzene (DVB)	SiC ceramic	-	The material exhibits a density of 2.20 g/cm3, with a porosity of 14%.	[159]
Polyvinylsilane (PVS)	Liquid thermosetting organo-silicic compound	SiC fiber-reinforced SiC matrix composites (SiC/SiC)	1	The material shows a relative density of 70%, corresponding to approximately 30% porosity.	[160]
Blend of polycarbosilane (PCS) and polymethylsilane (PMS)	Based on the above, combined with oxide fillers (BMAS/ZrSiO4 fillers)	SiC fiber-reinforced SiC matrix composites (SiC/SiC)	-	Near-stoichiometric SiC matrix (C/Si ≈ 1:1) achieved, with improved high-temperature strength (380 MPa at 1673 K). Densification data not reported.	[161]
Allylhydridopolycarbosilane (AHPCS)	The molecular structure contains allyl groups (–CH2–CH=CH2) and hydride groups (–Si–H)	SiC fiber-reinforced SiC matrix composite	-	The porosity is approximately 10%, with enhanced thermal diffusivity but reduced strength.	[162]

.

Finally, for the CVI process, the long preparation cycle and high cost limit its application. However, ceramics prepared by CVI exhibit high purity, high modulus, and high strength, making them primarily suitable for high-end and extreme environments where material purity is critical. It is generally recognized that ceramics fabricated via CVI still retain an approximate porosity of 10% [145]. Therefore, current research focuses on integrating CVI with other processes to manufacture high-end products that demand high strength, high purity, and high densification. Lv et al. [163] combined spray drying, binder jetting, and chemical vapor infiltration (CVI) to fabricate high-purity SiCW/SiC components, achieving a flexural strength of up to 200 MPa and a fracture toughness of 3.4 MPa·m^1/2. Baux et al. [164] integrated PIP, CVI, and CVD (chemical vapor deposition) to fabricate SiC ceramic components for solar energy receivers, resulting in a 100% increase in apparent density and an approximately 80% reduction in open porosity.

Comprehensive analysis indicates that BJ 3D printing technology combined with optimized densification post-processing can significantly improve the overall performance of SiC components. However, systematic comparison of key performance parameters between these and SiC samples prepared by other methods is required to fully evaluate the advantages and limitations of this technology in terms of material properties and industrial feasibility.

Firstly, among the improved techniques for traditional SiC component manufacturing reported in recent years, SiC samples fabricated by modified gelcasting and solid-state sintering exhibited a flexural strength of 128.0 MPa [165], while those prepared via pressureless solid-state sintering achieved a flexural strength of 443 ± 27 MPa [166]. Samples produced using microwave sintering assisted with a heat molding process demonstrated a bending strength of 492.7 ± 36.8 MPa [167], and those fabricated by spark-plasma sintering reached a relative density of 97.5 ± 0.6% of the theoretical value [168].

As evidenced by the comparative literature data in Section 3.2 of the manuscript, the flexural strength and densification rate of BJ 3D-printed SiC samples are generally lower than those obtained by improved traditional SiC manufacturing techniques (though the flexural strength exceeds that of samples fabricated via modified gelcasting and solid-state sintering). The density and bending strength of SiC samples produced by BJ 3D printing still fall short of the levels achieved by conventional SiC manufacturing methods and their improved variants. However, the advantages and potential of binder jetting 3D printing in producing large SiC components with complex geometries remain unmatched by traditional techniques.

Secondly, among other recently reported AM processes for SiC components, samples fabricated via material extrusion 3D printing combined with pressureless solid-state sintering exhibited a flexural strength of 397 ± 29 MPa (maintaining 382 MPa at 1700 °C) and a density of 3.06 g/cm³ [169]. SiC components produced via vat DLP followed by LSI achieved a density of 2.75 g/cm³ and a maximum flexural strength of 262.6 MPa [170]. Meanwhile, samples obtained through selective laser 3D printing integrated with PIP and liquid-phase sintering reached a peak flexural strength of only 150 ± 6 MPa [171].

As shown by the comparative data in Section 3.2, although the flexural strength of samples fabricated via BJ 3D printing (1) is significantly higher than that of selective laser printed specimens combined with PIP, (2) is slightly lower than those produced by vat photopolymerization, and (3) still falls short of the absolute values achieved by material extrusion with pressureless sintering, it is noteworthy that, by optimizing the composition of PIP precursors, BJ 3D-printed SiC parts have demonstrated comparable high-temperature flexural strength to those produced by extrusion-based methods (see the second-to-last row in Table 6). Moreover, while the density of SiC components produced by BJ 3D printing is generally lower than that of those fabricated via material extrusion with sintering or vat photopolymerization, this inherent characteristic offers a distinct advantage in weight-sensitive applications—such as aerospace thermal-end components—where a high strength-to-weight ratio is prioritized over absolute material density.

In conclusion, although extensive research has demonstrated that the mechanical properties of SiC components fabricated via BJ 3D printing still fall short of those produced by conventional manufacturing methods—particularly for extreme service conditions such as turbine blades or high-load-bearing structural components—the overall performance of BJ 3D-printed SiC parts already meets the integrated requirements for lightweight design, thermal stability, and chemical inertness in certain application fields. As outlined in this study, BJ 3D-printed SiC parts subjected to optimized LSI have achieved residual silicon contents as low as 5.2 vol%, which is well below the acceptable threshold (~10 vol% [172]) for aerospace and electronic applications. Through continued optimization of carbon control strategies (such as PRBI) and the development of advanced polymer-derived precursors, BJ-printed SiC components have demonstrated flexural strengths of 257 ± 14.26 MPa at room temperature and 380 MPa at 1673 K, fully satisfying the mechanical performance requirements for nuclear fuel cladding and non-load-bearing structural parts in aerospace applications. With further advances in this field, both the mechanical and thermal properties of BJ-fabricated SiC components are expected to continue improving.

3.3. Detection and Assessment Techniques

In the BJ 3D printing process, it is crucial to conduct performance testing on both green parts and final components after densification post-processing—the former evaluates forming quality and optimizes the debinding process, while the latter validates the material’s final performance and detects densification-induced defects. Their combination establishes a closed-loop quality control system throughout the entire manufacturing chain, providing dual assurance for process optimization and product reliability.

• Surface accuracy testing of green parts

Geometric and dimensional accuracy testing of green parts is a critical step in evaluating whether the BJ 3D printing process meets manufacturing performance requirements. The testing data serves as primary reference parameters for guiding both accuracy compensation design in post-processing stages and printing process optimization. For green parts, coordinate measuring machines (CMMs) generate detailed surface profiles and three-dimensional morphology data through scanning and point measurements, enabling calculation of surface roughness parameters [173]. CMMs provide sub-micrometer measurement accuracy and resolution, allowing high-precision measurements over large areas, making them suitable for complex geometries and large-sized components [174].

However, SiC ceramic components are characterized by high hardness and brittleness, and, during CMM inspection, the probe makes direct physical contact with the component’s surface, which may cause minor damage to fragile or delicate surfaces. Additionally, the size of the probe limits the minimum feature size that can be measured, which results in CMMs being insufficient for accurately measuring small surface details and complex microstructures of SiC ceramic printed parts. The coordinate measuring machine industry has numerous brands, including Sweden’s Serein, Germany’s AEH, America’s Leader, Germany’s WENZEL, Japan’s Mitutoyo, and China’s Aviation Precision 303, all of which hold significant advantages in brand image, product quality, innovative technology, and marketing strategies. Among the many coordinate measuring machine manufacturers, FARO is a globally recognized supplier of 3D technology, widely applied in the precision inspection of BJ 3D printing, dedicated to providing mature and comprehensive 3D measurement, imaging, and implementation solutions, with strong research and production capabilities and multiple international patents. Its products are mainly used in formation quality control and inspection, product design and engineering, layout design, and projection, enjoying a high level of recognition and reputation in the computer-aided measurement equipment industry, and its accuracy measurement schematic is shown in Figure 18.

From a cost perspective, coordinate measuring machines (CMMs) are more prevalent in binder jetting 3D printing inspection technologies when meeting the required printing accuracy specifications. In contrast to the point-measurement approach of CMMs, optical methods analyze geometric features and dimensional measurements by performing multi-directional scanning of surface profiles [175]. This non-contact characteristic ensures the absence of physical damage to the surfaces of SiC ceramic printed components, consequently enabling their widespread application in the performance evaluation of post-densification final parts. These optical methodologies will be comprehensively reviewed in the subsequent nondestructive testing section.

b.

Mechanical and thermal property testing of green parts

Mechanical and thermophysical property testing constitutes a critical evaluation for green parts, requiring multiple test protocols to comply with national assessment standards. Geometric and dimensional accuracy alone cannot serve as the sole parameter for determining printed part quality. For SiC 3D printing equipment, some high-temperature and high-pressure operating environments require printed parts to possess high tensile strength, flexural strength, compressive strength, and thermal performance indicators, to ensure the product’s lifespan. Evaluating these properties requires tensile testing, flexural testing, compressive testing, and thermodynamic testing. During the BJ 3D printing process, tensile test blocks, flexural test blocks, and compressive test blocks are printed alongside the printed parts.

After printing, the tensile specimens, flexural specimens, and compressive specimens (see Figure 19a,b) are extracted after depowering for relevant mechanical property testing, among which compressive strength testing is shown in Figure 19c.

It should be noted that the design of the aforementioned mechanical property test blocks must comply with national standards for mechanical performance evaluation, including ASTM D638 (tensile testing), ASTM D790 (flexural testing), and ASTM D695 (compressive testing). Common thermal performance evaluation standards include thermogravimetric analysis, differential scanning calorimetry, and thermal conductivity testing, among others [176,177].

c.

Nondestructive testing of final printed components

In the aforementioned mechanical property testing processes, the strength metrics of 3D-printed parts are analyzed by destroying a cross-section of the relevant test specimens, employing cross-sectional microstructural analysis to assess performance. This is also the main reason why this testing method cannot directly evaluate printed parts. The specimens used for mechanical property testing have simple structures, and, when inspecting complexly structured printed equipment, testing errors may be amplified due to the differing shapes and structures. Testing errors may therefore be magnified. However, with the development of testing technologies, nondestructive evaluation techniques have begun to be used for testing and inspection in manufacturing and service applications, to verify the quality and functionality of components [178]. Compared to methods such as cross-sectional microstructural analysis that require cutting SiC ceramic printed parts for performance analysis, the application of nondestructive evaluation does not cause damage to the produced BJ 3D-printed SiC ceramic parts; therefore, this testing method can be directly applied to the inspection and evaluation of printed parts, significantly reducing unnecessary errors. Some nondestructive testing methods can monitor the quality status of the internal or external surfaces of SiC ceramic printed parts in real time during the manufacturing process of BJ 3D-printed components, and the test results can be used to identify changes in process conditions and optimal process parameters, ensuring the stability and consistency of the printing process.

Table 7. Comparative analysis of nondestructive testing methods for final components.

Testing Methods	Testing Principle	Testing Parameters	Advantages	Disadvantages	Ref.
Scanning Electron Microscopy	The surface of the sample is scanned by an electron beam, and secondary electron signals are collected and converted into high-resolution images.	Surface morphology and defect characteristics (micron/nanometer scale)	Nanometer-scale resolution enables analysis of microscopic defect origins	The equipment is expensive, operationally complex, and time-consuming for inspection, with limitations to surface examination only.	[179]
Liquid Penetrant Testing	The dye penetrates surface defects through capillary action, and color distribution is observed after development.	Surface-breaking defects (cracks, pores)	Cost-effective, operationally simple, and suitable for simple structural components	Highly susceptible to surface roughness effects, requiring pretreatment; limited to surface defect detection only.	[180,181]
Computed Tomography	X-rays penetrate the sample, and the internal structure is visualized through three-dimensional reconstruction.	Internal defects (porosity, crack distribution, density)	High resolution (micron-scale) enabling three-dimensional visualization of internal defects	The equipment exhibits high costs, slow inspection speed, and limitations for large-sized components.	[182,183]
Ultrasonic Testing	High-frequency acoustic waves propagate through the material, and internal defects are analyzed by reflected signals.	Internal defects (cracks, delamination), thickness measurement	Capable of inspecting thick components with relatively low cost and high portability	Requires surface planarization treatment and presents difficulties in inspecting components with complex geometries.	[180]
Thermal Imaging Technology	The surface temperature field is captured by an infrared camera after thermal excitation, and anomalies caused by thermal conductivity differences are analyzed.	Internal defects (porosity, delamination), thermal properties	Rapid large-area inspection suitable for online monitoring	Relatively low accuracy (millimeter-scale) with incapability for quantitative defect size analysis.	[184,185]

summarizes the detection principles of various nondestructive testing methods and provides a comparative analysis of their advantages, disadvantages, and applicable scopes.

In summary, after the formation of SiC components via BJ 3D printing, the methods for inspecting and evaluating the components should be weighed from multiple perspectives. These perspectives include not only technical performance, but also economic factors, component complexity, application scenarios, and more. First, the complexity of the printed component will influence the choice of inspection methods. Complex geometries may require nondestructive testing methods such as computed tomography scanning, while simpler-shaped components may only require standard mechanical performance testing. Secondly, from the perspective of size, small components may require high-resolution microscopic inspection tools, whereas large components may need low-resolution methods that can quickly cover the entire part. Furthermore, application scenarios and working environments will affect the focus of inspection; for example, components in aerospace or nuclear industries require high-precision defect detection. In addition, economic cost is also a factor that must be considered. High-precision nondestructive testing can be costly but may be essential for critical functional parts. Finally, efficiency is also a critical aspect, as components produced in large quantities require fast and automated inspection methods. A reasonable inspection and evaluation approach should be the result of a comprehensive consideration of the component’s geometric complexity, material performance requirements, economic factors, production efficiency, and application scenarios. Its selection not only should ensure product quality and optimize production processes, but is also closely related to production efficiency and manufacturing costs.

4. Practical Applications and Case Studies

This section primarily surveys and analyzes the major forming equipment and application cases in the field of SiC powder 3D printing with droplet jetting technology from several well-known companies. The companies involved include Oak Ridge National Laboratory, the CONCR3DE and WZR collaboration team, Schunk Technical Ceramics, Saint-Gobain, SGL Carbon, Terrani, Farsoon Technologies, BLT, and Aurora Innovation. Each piece of equipment from these companies has distinct characteristics in SiC 3D printing, with some focusing on material property development and others on breakthroughs in equipment technology, providing diverse solutions for the advancement of SiC powder 3D printing. To meet the demand for high-precision, complex SiC components, companies are actively researching the preparation and processing of SiC. Oak Ridge National Laboratory [186] has successfully combined binder jet printing with chemical vapor infiltration (CVI) to produce high-purity, fully crystallized SiC components suitable for applications requiring high thermal conductivity and mechanical strength with complex geometries. The CONCR3DE and WZR collaboration team [187] has studied water-based binders and particle-filled binders to significantly enhance the density and mechanical properties of SiC materials, expanding their potential applications across various industrial sectors. ExOne, in collaboration with Saint-Gobain, has made breakthroughs in SiC BJ 3D printing technology, supporting the large-scale production of complex, high-performance components and promoting technological advancement in the field [188,189].

Schunk Technical Ceramics’ IntrinSiC process has shown excellent performance in aerospace, providing lightweight components for high-temperature, high-strength applications. Saint-Gobain’s ExOne BJ systems have made significant progress in printing precision and material compatibility, supporting the application of SiC in high-temperature, corrosion-resistant equipment [190]. SGL Carbon focuses on the development of SiC components for high-temperature and corrosive environments, particularly in metallurgy applications [191]. Terrani specializes in nuclear industry applications, developing SiC fuel components for high-temperature and radiation environments that meet the strict requirements of nuclear reactors.

Farsoon Technologies, BLT, and Aurora Innovation [192] continue to push the optimization of droplet jetting technology. Farsoon’s high-precision droplet jetting system has increased the printing speed and accuracy of SiC components, further advancing the application of ceramic materials. BLT’s SiC 3D printer has shown application potential in aerospace, particularly for manufacturing high-temperature structural components. Aurora Innovation has optimized material uniformity and printing precision, reducing material waste and offering new insights for the sustainable development of 3D printing technology.

Through these technological advancements, we foresee a broader application of SiC powder 3D printing in the future, especially in the aerospace, defense, and nuclear energy sectors. SiC materials, with their excellent thermal stability, mechanical strength, and radiation resistance, will play a critical role in the manufacturing of high-performance components. Additionally, with the continuous optimization of droplet jetting technology, SiC 3D printing will see improved production efficiency and forming quality, driving the technology toward large-scale, customized production. In the future, SiC powder 3D printing technology will continue to make breakthroughs in enhancing forming precision, reducing material waste, and expanding material adaptability, further promoting its application across multiple high-end fields.

Based on the current literature and industrial survey results presented in this manuscript, reports on the real-world commercial applications of BJ 3D-printed SiC components remain extremely limited. Most studies are still at the laboratory or prototype validation stage, with research efforts primarily focused on microstructural control, mechanical performance evaluation, and process optimization. The technology has not yet been widely adopted in practical applications. Although SiC components fabricated via BJ technology exhibit promising potential for use in critical sectors such as aerospace systems, high-temperature filtration, wear-resistant components, and energy-related equipment, numerous challenges remain in translating laboratory-scale advances into industrial implementation. These challenges include:

(1)

Lack of industry standards and regulatory guidelines: At present, there are fewer national or international standards specifically addressing BJ-fabricated ceramics, particularly SiC structural components. This results in the use of disparate testing protocols and performance evaluation criteria across different research groups and industrial entities, making cross-comparison and standardized adoption difficult. Consequently, this lack of standardization hinders the integration of BJ SiC components in high-reliability application scenarios.

(2)

Insufficient validation of material performance: Although the mechanical properties of BJ-formed SiC components have shown encouraging results, most data are derived from small-scale specimens. Comprehensive performance validation for large-scale or geometrically complex parts remains scarce, limiting confidence in their structural reliability.

(3)

Process variability and performance reproducibility: Significant fluctuations in binder distribution and post-processing steps can lead to inconsistencies in microstructure and mechanical properties. This lack of reproducibility undermines the reliability assessments required for critical load-bearing applications.

(4)

High cost and limited economic viability: The overall cost of BJ-produced SiC remains high due to the use of high-purity, ultrafine powders, expensive binder jetting equipment, and energy-intensive high-temperature post-processing. Additionally, long processing times and moderate yields reduce economic competitiveness. Strategies such as powder recycling, process shortening, and yield improvement are needed to enhance cost efficiency.

(5)

Insufficient engineering-scale validation and environmental adaptability: Current BJ SiC research is largely confined to laboratory-scale samples. There is a lack of long-term performance data under realistic service conditions, such as high-temperature oxidation, thermal shock, corrosive environments, or particle erosion, which are essential for assessing their durability and reliability in demanding operational settings.

(6)

Controlling process-related defects remains highly challenging. The BJ process inherently suffers from issues such as weak interlayer bonding, non-uniform powder packing density, and trade-offs between layer thickness and feature resolution. During post-processing, even slight variations in parameters such as carbon source incorporation, pyrolysis shrinkage, and silicon infiltration pathways can readily induce defects such as cracking, porosity, warping, and non-uniform silicon infiltration. These issues significantly compromise the final densification and mechanical performance of the printed SiC components.

5. Future Perspectives

5.1. Technological Development Trends

The combination of droplet jetting technology and SiC powder 3D printing is expected to achieve significant advancements in precision, printing efficiency, material and functional diversification, and automation of intelligent control in the future. These technological improvements are essential for the widespread application of SiC powder 3D-printed products in industries such as mechanical engineering, healthcare, and aerospace.

First, improving the precision of jetting control will be one of the core drivers of technological progress. By optimizing the design of droplet jetting equipment, improving printhead structure, and applying more advanced control algorithms, the precision of droplet size and jetting position can be significantly improved, thereby enhancing the resolution and surface quality of printed products [193]. Precise control over droplet formation and deposition helps address current issues related to layer thickness control and edge effects, ensuring superior performance in the high-precision manufacturing of complex structures. Secondly, increasing printing speed and efficiency is key to enabling industrial application of this technology. In this regard, future advancements may involve improving layer thickness process planning, implementing grayscale printing, optimizing material supply systems, and utilizing new high-speed droplet jetting printheads. These methods can significantly reduce the printing cycle, especially in the production of large-size and complex geometric structures [194]. This improvement will not only enhance production efficiency, but also increase the feasibility of SiC powder 3D printing technology for large-scale production. Additionally, material diversification and functional integration will be key research directions in the future. The application of SiC powder 3D printing technology will expand from single materials to functional composites, smart materials, and nanomaterials, helping to overcome the limitations of traditional materials and achieve functional integration in printed products. By integrating new materials with intelligent design, future printed products will possess various integrated functions, such as sensing and thermal management [195,196,197]. Moreover, the development of intelligent and automated control technologies will further advance droplet jetting technology. With the integration of artificial intelligence, machine learning, and sensor technologies, future printing processes will enable real-time data collection and feedback control. By continuously monitoring and adjusting jetting parameters and material conditions in real time, the printing process can be optimized to ensure product consistency and quality [198]. Such data-driven adaptive control systems are expected to enable full automation of the droplet jetting 3D printing process, improving production efficiency while ensuring the stability of product quality.

5.2. Expansion of Application Fields

As SiC powder 3D printing technology continues to evolve, its potential applications to emerging fields are becoming increasingly important. In addition to traditional industrial applications, SiC materials show great potential for use in the biomedical field, renewable and clean energy, and the aerospace sector [199,200,201,202].

5.2.1. Biomedical Field

SiC materials, due to their excellent corrosion resistance and good biocompatibility, have garnered significant attention in the biomedical field in recent years. Although SiC has primarily been used in industrial applications such as high-temperature structural components and wear-resistant tools, its potential in biomedical applications is gradually emerging [203]. For instance, SiC’s corrosion resistance enables it to remain stable in bodily fluids, while its excellent biocompatibility makes it an ideal material for manufacturing high-strength, durable medical implants and dental instruments. With 3D printing technology, SiC can be precisely fabricated into personalized medical devices that conform to human anatomical structures, opening up new possibilities for personalized medical solutions in the future. However, despite the great potential of SiC in biomedical applications, it has not yet become a mainstream choice for implants due to challenges such as binder removal during post-processing. Ongoing research is exploring ways to improve post-processing techniques and alternative binders, and advancements in these areas may eventually make SiC a promising material for biomedical use.

5.2.2. New Energy and Clean Energy Technologies

In the field of new energy and clean energy, SiC materials exhibit broad application potential due to their high thermal conductivity, high temperature resistance, and excellent oxidation resistance. Especially under high-temperature conditions, SiC materials can effectively improve the efficiency of thermal management systems and reduce the energy consumption of equipment [204]. Through SiC 3D printing technology, complex structures such as heat sinks, heat exchangers, and core components for energy conversion devices can be manufactured, further enhancing the overall performance of new energy systems. Additionally, SiC’s chemical stability and structural durability make it highly promising for future applications in clean energy fields, such as solar cell and fuel cell components.

5.2.3. Aerospace Field

With the growing demand for lightweight, high-strength materials, the application of SiC materials in the aerospace field is becoming increasingly important. SiC materials, due to their exceptional strength, high temperature resistance, and outstanding mechanical properties, have become the ideal material for manufacturing key components such as aircraft engine parts and turbine blades [205,206]. Using 3D printing technology, SiC parts with complex geometries can be precisely fabricated, meeting the aerospace industry’s stringent requirements for lightweight, high-performance structural components. Furthermore, the high thermal stability and oxidation resistance of SiC make it highly promising for applications in extreme environments, such as space exploration and the manufacturing of high-temperature aircraft components.

As SiC powder 3D printing technology continues to advance, its potential applications in emerging fields such as biomedical science, renewable and clean energy, and aerospace are becoming increasingly promising. This technology offers more flexible and efficient solutions for manufacturing high-precision, complex structural components, driving the application and development of SiC materials in a broader range of fields. Moreover, the expansion of these applications will create new opportunities for future technological innovation and further promote deep integration of 3D printing technology into these sectors.

5.3. Key Focus Areas for Research and Development

Based on a systematic review of existing literature and research on actual companies, it can be predicted that the future research and development of SiC powder 3D printing technology will focus primarily on technological breakthroughs and process optimization. To drive the industrial application of this technology, key areas of research will focus on material performance optimization, process parameter matching, and intelligent formation quality control.

First, material performance optimization is key to improving the quality of printed parts. The physical properties of SiC powder, such as particle size distribution, morphology, and interaction with binders, directly affect the surface quality, mechanical properties, and internal structural uniformity of printed products. Future research should deeply explore the impact of these factors on the quality of printed parts, optimize the pretreatment processes of SiC powder, and improve its flowability and bonding characteristics [205]. For example, precise control of powder particle size and morphology can reduce porosity during the printing process, increase the density and strength of printed parts, and meet the requirements for manufacturing complex structures. Secondly, matching binders with printing parameters is a critical aspect of process development. Selecting appropriate binders and optimizing jetting parameters is essential to meet the diverse demands of different application scenarios and product structures. This not only helps improve the mechanical properties and dimensional accuracy of the printed parts, but also enhances the interlayer bonding strength and uniformity during the printing process [207]. Future research should focus on exploring how to select optimal binder composition and viscosity based on the characteristics of different materials, combined with key process parameters such as jetting speed and droplet volume, to develop efficient and reliable forming processes. Additionally, innovations in formation quality control technology are central to ensuring product consistency and precision in printing. As 3D printing technology moves toward large-scale production, integration of real-time monitoring and closed-loop control systems will become a key research focus. AI-based and sensor technologies can enable real-time monitoring and automatic adjustment of key parameters during the printing process, thereby improving the consistency and quality of printed parts [207]. For example, by collecting real-time data on jetting parameters, material conditions, and printed parts, feedback control can automatically adjust variables such as jetting speed and temperature to respond to potential process fluctuations. This intelligent and automated formation quality control system can not only improve production efficiency, but also significantly reduce scrap rates and production costs, advancing SiC powder 3D printing technology toward industrialization and standardization.

Future research and development of SiC powder 3D printing technology will focus on material optimization, process parameter matching, and intelligent formation quality control. With continuous technological breakthroughs and process improvements, the application potential of SiC 3D printing technology in the manufacturing of complex parts will be further unlocked.

6. Conclusions

This paper presents a comprehensive and systematic review of BJ 3D printing technology for SiC powders, with an in-depth exploration of the research status, challenges, and future trends in the preparation and applications of high-performance SiC-based components.

BJ 3D printing technology has been successfully applied in the rapid prototyping of SiC powders, with small-scale forming equipment currently in operation. At the specialized equipment level, advanced devices such as piezoelectric printheads provide robust support for high-precision printing of SiC components. Regarding processing technology, significant progress has been made in optimizing key aspects, including SiC powder preparation, binder selection, and curing and sintering processes, as well as complete workflow improvements encompassing pre-processing, printing, and post-processing. The preparation of spherical powders through ball milling and spray drying techniques has effectively improved powder flowability. The use of multimodal powders enhances powder bed density, while optimization of printing parameters has led to noticeable improvements in printing quality.

Quality control during green body formation and post-processing is crucial for manufacturing high-quality SiC components. During green body formation, powder particle size and shape must be optimized by preparing powders with appropriate particle sizes to improve printing resolution. The use of spherical powders or nanoparticle flow agents enhances both flowability and packing density. Additionally, binder parameters such as viscosity and surface tension must be controlled to prevent satellite droplets and nozzle clogging, minimize powder splattering, and appropriately adjust saturation levels to avoid layer shifting and dimensional errors. For printing parameters, optimizing roller rotation direction, speed, and lateral movement speed is essential for ensuring powder bed quality. Selecting appropriate powder layer thickness and particle size can suppress the stair-stepping effect, thereby improving precision. During post-processing, continuous optimization of post-treatment processes is required to achieve final part densification, such as reducing residual liquid silicon in LSI and minimizing internal cracks after PIP. Finally, employing various inspection technologies can promptly identify and resolve issues, providing data support for subsequent process optimization.

Current challenges in SiC powder 3D printing are as follows. In process research, the complex physicochemical properties of SiC powder and unclear interaction mechanisms with binders make green body formation difficult to control and complete densification of final SiC components hard to achieve. Cost-wise, high R&D expenses limit optimization and practical application of green body formation and densification post-processing, while acquisition costs for high-quality specialized equipment and materials remain substantial. Balancing quality improvement with efficiency presents another major challenge—for instance, reducing powder layer thickness improves precision but decreases efficiency during green body formation, while combining CVI, PIP, and CVD in post-processing achieves extremely high densification but significantly extends processing time. Additionally, limitations exist in testing technologies; although nondestructive testing is crucial for inspecting SiC components, it is constrained by inspectable part size and detection efficiency, which in turn are affected by part size and resolution.

Current research trends in BJ 3D printing technology for SiC applications include (1) advancing technological progress by optimizing techniques, improving equipment, and refining algorithms to enhance product resolution and surface quality; (2) emphasizing efficiency improvements and exploring new methods to increase printing speed and throughput for mass production; (3) pursuing material and functional diversification by extending into areas like functional composites to achieve integrated functionality; (4) developing toward intelligent control and automation through artificial intelligence, real-time data acquisition, and feedback control systems to improve production efficiency and quality stability; and (5) expanding SiC application fields by seeking innovative solutions in emerging areas such as biomedicine and renewable energy.

In conclusion, while BJ 3D printing technology shows tremendous promise in the SiC field, significant challenges remain. Future research should focus on addressing these issues to further advance and broaden the technology’s depth and scope, promoting the continuous development of binder jetting 3D printing for SiC powders, ultimately providing novel solutions for innovation and progress across various industries.