Search Results (314)

Additive manufacturing (AM) has emerged as an enabling technology for producing lightweight and geometrically complex components in aerospace applications. This study investigates alternative manufacturing routes for a critical servo bracket used in a Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicle (UAV) platform, aiming to comparatively evaluate their environmental, economic, and operational performance within a life cycle perspective. The servo bracket was manufactured using CNC milling, Selective Laser Melting (SLM), and Metal Extrusion Additive Manufacturing (MEX/M) and the three routes were assessed using Life Cycle Assessment (LCA), Life Cycle Cost (LCC), and process-based indicators, including production time and production process. The results indicate that CNC milling exhibits the highest carbon footprint per part (156.3 kg CO₂-eq.), mainly due to aluminium chip waste, whereas electricity consumption is the dominant contributor in SLM. Production times were 8.9 h for CNC, 52.7 h for SLM, and 71.6 h for MEX/M. From an economic perspective, CNC provides the lowest unit cost, while SLM is associated with the highest cost due to machine depreciation. Overall, the findings highlight distinct trade-offs between conventional and metal additive manufacturing routes and provide a life cycle-based decision framework for selecting suitable manufacturing strategies for VTOL UAV structural components. Full article

Selective laser melting (SLM), a pivotal additive manufacturing (AM) technology for titanium alloys, enables near-net-shape forming of complex structures with relative densities of up to 99.9%, making it indispensable in aerospace, biomedical, and marine engineering. This review comprehensively updates the state of the art on SLM-fabricated TC4 (Ti-6Al-4V) alloy, addressing critical gaps in previous studies by integrating novel research progress, in-depth mechanistic analyses, and multi-dimensional comparisons. The core focus is on the unique thermal cycle (10⁶–10⁸ °C/s heating/cooling rates) of SLM, which induces a predominant needle-like martensitic α′ phase (99.7%) and minimal β phase (0.3%), leading to intrinsic anisotropy and low ductility. Room-temperature tensile strength reaches 1315.32 MPa with 9.6% elongation, and high-cycle fatigue limits the range from 417 to 829 MPa, strongly dependent on process parameters and post-treatment. Corrosion anisotropy is systematically analyzed: the XY plane (parallel to scanning direction) exhibits superior corrosion resistance in 1 M HCl (fewer pits and lower corrosion current density) and 3.5% NaCl (more stable passive film) compared to the XZ plane (deposition direction). Novel insights include: (1) synergistic effects of SLM process parameters (laser power–scanning speed–hatch spacing) on defect evolution and microstructure uniformity; (2) atomistic mechanisms of α′→α + β phase transformation during post-heat treatment; and (3) corrosion–mechanical coupling behavior in harsh environments (e.g., marine and biomedical). Post-treatment strategies are refined: annealing at 800 °C for 2 h achieves 1099 MPa tensile strength and 17.4% elongation, while hot isostatic pressing (HIP) reduces porosity from 0.08% to 0.01% and weakens fatigue anisotropy. This review also identifies unresolved challenges (e.g., in situ defect monitoring and multi-field regulated performance) and proposes future directions (e.g., AI-driven process optimization and functional gradient structures). Full article

Selective Laser Melting (SLM), as a common metal additive manufacturing (AM) technology, achieves high-precision complex part formation by layer-by-layer melting of metal powder using a laser. However, the dynamic behavior of the melt pool during the SLM process is influenced by the heat source model, which is crucial for suppressing porosity defects and optimizing process parameters, directly determining the reliability of numerical simulations. To address the issue of traditional surface heat source models overestimating the melt pool width and volume heat source models underestimating the melt pool depth, this study constructs a three-dimensional transient heat conduction finite element model based on ANSYS Parametric Design Language (APDL) to simulate the evolution of the temperature field and melt pool geometry under different laser parameters. First, the temperature fields and melt pool morphology and dimensions of four heat source models—Gaussian surface heat source, volumetric heat source models (rotating Gaussian volumetric heat source, double ellipsoid heat source), and a combined heat source model—were investigated. Subsequently, a dynamic heat source model was proposed, combining a Gaussian surface heat source with a rotating volumetric heat source. By dynamically allocating the laser energy absorption ratio between the powder surface layer and the substrate depth, the influence of this heat source model on melt pool size was explored and compared with other heat source models. The results show that under the dynamic heat source, the melt pool width and depth are 128.6 μm and 63.13 μm, respectively. The melt pool width is significantly larger compared to other heat source models, and the melt pool depth is about 17% greater than that of the combined heat source model. At the same time, the predicted melt pool width and depth under this heat source model have relative errors of 1.0% and 5.5% compared to the experimental measurements, indicating that this heat source model has high accuracy in predicting the melt pool’s lateral dimensions and can effectively reflect the actual melt pool morphology during processing. Full article

Additive manufacturing (AM) has emerged as a key enabling technology in contemporary dental manufacturing, driven by its capacity for customization, geometric complexity, and seamless integration with digital design workflows. This article presents a technology-oriented narrative review of additive manufacturing in dental implant production, focusing on dominant processing routes, material systems, and emerging research trends rather than a systematic or critical appraisal of the literature. An indicative descriptive analysis of publications indexed in the Web of Science and Scopus databases between 2014 and 2024 was used to contextualize the technological development of the field and identify major research directions. Emphasis was placed on metal powder bed fusion technologies, specifically Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS), which enable the fabrication of titanium implants with controlled porosity and enhanced osseointegration. Ceramic AM approaches, including SLA, DLP, and PBF, are discussed in relation to their potential for aesthetic dental restorations and customized prosthetic components. The publication trend overview indicates a growing interest in ceramic AM after 2020, an increasing focus on hybrid and functionally graded materials, and persistent challenges related to standardization and the availability of long-term clinical evidence. Key technological limitations—including manufacturing accuracy, material stability, validated metrology, and process reproducibility—are highlighted alongside emerging directions such as artificial intelligence-assisted workflows, nanostructured surface modifications, and concepts enabling accelerated or immediate clinical use of additively manufactured dental restorations. Full article

Selective laser melting (SLM) is a 3D printing technology for precision manufacturing. Owing to its high forming accuracy, parts fabricated by SLM can often be used directly without secondary machining. Consequently, the stress field in the structure, especially local stress concentration in small regions, is of great importance. Building on our previous work, this study proposes an accurate and efficient thermo-mechanical analysis method that combines a computational fluid dynamics (CFD) model and a finite element method (FEM) model for stress prediction in micrometer-scale SLM. Compared with the conventional element birth–death method, the present model more faithfully reproduces the SLM process and the post-solidification morphology and stress distribution. Numerical simulation of a single-track TC4 scan shows that pronounced surface undulations and lack-of-fusion regions exhibit significant stress concentration: the local residual stress can reach approximately 900 MPa, whereas regions with relatively smooth surface geometry exhibit stresses of about 650 MPa. This indicates a clear positive correlation between surface quality and stress concentration. The results provide a new theoretical basis for understanding defect formation mechanisms, spatial stress distribution, and scan-path optimization in SLM components. Full article

Selective laser melting (SLM) is a key technology in metal additive manufacturing (AM), but the widespread presence of porosity defects in fabricated parts significantly degrades mechanical performance and limits practical applications. Machine learning (ML) and deep learning (DL) have shown great potential in porosity prediction, defect detection, and performance modeling. However, their application remains constrained by the lack of systematic “processes–images–properties” datasets and the high cost of experimental data acquisition. To address this challenge, this study proposes an innovative normalization method for multi-source SLM porosity images (NMI). The method integrates scale bar detection and removal, physical size normalization, and resolution harmonization to ensure dimensional consistency while preserving critical pore features. Systematic validation using both literature-derived and experimental datasets demonstrates that NMI effectively integrates heterogeneous image data, enhances dataset consistency, and promotes the reuse of existing imaging resources. This framework provides a scalable and resource-efficient pathway for DL-based defect prediction and process optimization, and establishes a solid foundation for constructing standardized and extensible materials datasets. Full article

Introduction: The success of metal–ceramic restorations depends on the mechanical and adhesive properties of the metal–ceramic interface. With the emergence of additive manufacturing technologies such as selective laser melting (SLM), there is growing interest in comparing these methods with conventional casting. This pilot study aimed to generate hypothesis-forming data on how fabrication method (casting and 3D printing) and alumina sandblasting with two particle sizes (125 μm and 250 μm) influence flexural performance of Co-Cr metal–ceramic systems within the standardized ISO 9693 framework. Materials and Methods: Rectangular Co-Cr alloy specimens were manufactured using two techniques: conventional casting and 3D printing via SLM. Each group was divided based on the sandblasting particle size. After ceramic application in accordance with ISO 9693:2012, samples underwent a three-point bending test using a universal testing machine (Instron 8872) to assess the displacement force required to fracture the ceramic layer. Five specimens were tested per group, and mean values and standard deviations were calculated. Data were statistically analyzed using two-way ANOVA followed by Tukey’s HSD post hoc test (p < 0.05). Results: Cast samples exhibited significantly higher displacement strength than printed ones. Among all groups, the cast samples sandblasted with 250 μm particles (CCT_250) showed the best performance (mean: 12.48 ± 0.91 N), while the 3D-printed group treated with 125 μm particles (CCP_125) showed the lowest strength (mean: 7.24 ± 0.65 N). Larger abrasive particles (250 μm) improved bond strength in both fabrication techniques. Two-way ANOVA revealed significant main effects of manufacturing method (F(1,16) = 13.63, p = 0.002, η² = 0.46) and particle size (F(1,16) = 6.17, p = 0.024, η² = 0.28), with no interaction between factors. Conclusions: Both the manufacturing method and the sandblasting protocol significantly influence the flexural performance of Co-Cr ceramic systems. Conventional casting combined with 250 μm particle sandblasting ensures the highest ceramic adhesion, while SLM-printed substrates may require additional surface treatments to improve bonding efficiency. Complementary surface treatments such as bonding agents or chemical oxidation may enhance the metal–ceramic bond in SLM-fabricated frameworks. Full article

Additive manufacturing (AM) is finding increasing application in engineering, especially in manufacturing. As a result, new designs and machines not previously possible due to the restrictions of conventional manufacturing methods may be made. Nevertheless, the same AM parts require post-processing using conventional machining methods such as turning which is the subject of this study. This study provides a comparative analysis of the technological assurance of Ti-6Al-4V parts made via AM using selective laser melting (SLM) and conventional manufacturing methods. The effects of machining parameters such as cutting speed, depth of cut, and feed on the surface roughness of machined Ti-6Al-4V parts are studied. The study concluded that at low feed (0.12 mm/rev.) and low and average depth of cut (0.3 mm and 0.5 mm), the best surface roughness was obtained on the 3D printed samples rather than on the samples obtained using the conventional manufacturing method. In addition, an alternative surface roughness measurement scheme is proposed, which not only allows for measuring the surface roughness, including multiple aspects, but also for identifying possible surface defects in AM parts. Full article

The aim of this work is to investigate the effect of annealing (at temperatures ranging from 260 °C to 530 °C) of thin-walled Al-Mn-Mg-Ti-Zr samples manufactured by selective laser melting (SLM) on their tensile mechanical properties, hardness, and surface roughness. The results of this study may contribute to the development of post-processing modes for thin-walled products made of corrosion-resistant aluminum alloys with increased strength, manufactured using SLM technology. Hierarchical clustering methods allowed us to identify three groups of thin-walled samples with different strain-hardening mechanisms depending on the annealing temperature. The greatest hardening is achieved in the first group of samples annealed at 530 °C. Metallographic analysis showed that at this heat treatment temperature, there are practically no micropores (macrodefects) and microcracks. X-ray phase analysis showed the precipitation of Ti and Zr, as well as the formation of an intermetallic phase with a composition of Mg8Al16. At lower heat treatment temperatures, from 260 °C to 500 °C, the observed hardening is statistically significantly lower than at 530 °C. This phenomenon, combined with the formation of intermetallic phases and the precipitation of titanium/zirconium, contributes to the hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM. The main results of this study show that the optimal strain hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM is achieved by heat treatment at 530 °C for 1 h. The strengthening mechanism has two characteristics: (1) dispersion strengthening due to the formation of precipitates and (2) reduction in macrodefects at high temperatures. Full article

This study addresses the challenges of efficiency and cost in traditional sulfur hexafluoride (SF₆) degradation methods and the throughput limitations of common plasma technologies, with the aim of promoting sustainable treatment of potent greenhouse gases. A method of premixing SF₆ with plasma media before entering the plasma discharge region was employed to systematically investigate the effects of three atmospheres—nitrogen, air, and hydrogen—on the degradation efficiency, product distribution, and energy efficiency of SF₆. An experimental setup was constructed, and Gibbs free energy minimization simulations were conducted to analyze the degradation performance under different conditions. The results show that the premixed gas injection method achieves a degradation removal efficiency of over 99.84% when the SF₆ flow rate is lower than 4 slm, which is significantly better than the staged mixing method. When the discharge current increases from 40 A to 100 A, the degradation effect of SF₆ improves significantly, but the improvement becomes marginal when the current is further increased to 120 A. Compared with nitrogen, air and hydrogen atmospheres can effectively enhance the degradation removal rate, with the air atmosphere achieving the highest energy yield of 271 g/kWh. This research reveals the regulatory mechanism of medium components on SF₆ degradation, providing a theoretical basis for the sustainable, full-process treatment of industrial-scale reactors and contributing to the mitigation of greenhouse gas emissions. Full article

This study investigates how scanning speed influences the electrochemical performance and discharge behavior of aluminum–air (Al–air) batteries with CeO₂/Al6061 anodes fabricated through selective laser melting (SLM). Al–air batteries, celebrated for their exceptional energy density and eco-friendliness, encounter hurdles in their widespread application due to anode self-corrosion and the formation of passivation films. To address these challenges, this study integrates CeO₂-reinforcing phases into Al6061 alloys and leverages SLM technology to enhance anode performance. A comprehensive analysis was conducted on the effects of varying scanning speeds (800, 900, 1000, 1100, and 1200 mm/s) on the surface morphology, density, self-corrosion rate, electrochemical performance, and discharge behavior of the anodes. The findings reveal that a scanning speed of 1000 mm/s produces anodes with optimal density, minimal self-corrosion, and outstanding electrochemical and discharge performance. Specifically, this scanning speed leads to a high discharge voltage of 1.575 V and an anode utilization rate of 72.2%, which can be attributed to the complete melting of the powder and the formation of a uniform microstructure. These insights offer valuable guidance for the development of high-performance Al–air batteries, promising extended lifespans and enhanced efficiency. Full article

The primary objective of this research is to simplify and make the industrial manufacturing process of coated maraging steels more economical by combining the advantages of additive manufacturing with simultaneous bulk (aging) and surface (nitriding) treatment in an effective manner. With this aim, preliminary experiments were performed that demonstrated the hardness (and related microstructure) of an as-built MS1 maraging steel, produced by selective laser melting (SLM), is comparable to that of the bulk maraging steel products treated by conventional solution annealing. The direct aging of the solution-annealed and as-built 3D printed maraging steel resulted in similar hardness, indicating that the kinetics of the precipitation hardening process are identical for the steel in both conditions. This assumption was strengthened by a thermodynamic analysis of the kinetics and determination of the activation energy for precipitation hardening using Differential Scanning Calorimetry (DSC) measurements. Industrial target experiments were performed on duplex-coated SLM-printed MS1 steel specimens, which were simultaneously aged and salt-bath nitrided, followed by PVD coating with three different ceramic layers: DLC, CrN, and TiN. For reference, similar duplex-coated samples were used, featuring a bulk Böhler W720 maraging steel substrate that was solution annealed, precipitation hardened, and salt-bath nitrided in separate steps, following conventional procedures. The technological parameters (temperature and time) of the simultaneous nitriding and aging process were optimized by modeling the phase transformations of the entire heat treatment procedure using DSC measurements. A comparison was made based on the in-depth hardness profile estimated by the so-called expanding cavity model (ECM), demonstrating that the hardness of the surface layer of the coated composite material systems is determined solely by the type of the coatings and does not influenced by the type of the applied substrate materials (bulk or 3D printed) or its heat treatment (whether it is a conventional, multi-step treatment or a simultaneous nitriding + aging process). Based on the research work, a proposal is suggested for modernizing and improving the cost-effectiveness of producing aged, duplex-treated, wear-resistant ceramic-coated maraging steel. Full article

The quality of SLM formed parts is one of the key factors of the promotion and application of additive manufacturing technology. The scanning strategy fundamentally affects the fatigue life of SLM 316L stainless steel parts by regulating residual stress, defect distribution, and microstructure. Three different scanning strategies (meander scanning, stripe scanning, and chessboard scanning) were adopted to prepare the specimens. High cycle fatigue loading was applied to SLM 316L stainless steel specimens prepared by different scanning strategies. The thermal conductivity characteristics during the SLM part forming process were analyzed based on scanning electron microscopy observations of microstructure of SLM specimens, and the mechanism of residual stress and internal defect generation were revealed. The scanning direction determines the growth direction of the grains, thereby affecting the anisotropy and overall fatigue performance of SLM 316L stainless steel parts. The scanning path determines the overlap and lap joint of the melt pool, directly affecting the number, size, and location of pores and incomplete fusion defects. The scanning strategy affects the distribution and magnitude of residual stresses by changing the path of heat source movement. Theoretical analysis and experimental verification results indicate that the selection of a scanning strategy is an effective method for optimizing the fatigue performance of SLM parts. Full article

With the rapid development of additive manufacturing technology, selective laser melting (SLM) of austenitic stainless steel has been widely used. SLM stainless steel will inevitably deform during service, so it is necessary to study the microstructure and macro properties of post-plastic deformed SLM stainless steel. In this paper, the changes in the microstructure, mechanical properties, and corrosion resistance of SLM304 stainless steel after stretch deformation were studied, and the evolution rules were revealed. The results show that, with an increasing plastic deformation amount, SLM304 stainless steel exhibits grain fragmentation, disordered orientation, and subgrain formation, along with changes in the shape and size of the cellular structure. Additionally, the α’ martensite content inside SLM304 stainless steel rises significantly, while the thickness of the surface passivation film slightly decreases. The analysis shows that the combined effect of the complex microstructure makes the nanohardness of SLM304 stainless steel increase with the increase in the stretch deformation amount while its corrosion resistance deteriorates. Therefore, moderate post-plastic deformation can enable SLM stainless steel to balance excellent mechanical and corrosion properties. This study can not only provide a theoretical reference for the performance optimization of additive manufacturing steel but also provide value for the engineering application of additive manufacturing technology. Full article

Additive manufacturing techniques, such as selective laser melting (SLM), enable the production of intricate and integrated components made from metallic materials with inherent porosity. The pores, typically perceived as defects, are commonly observed on the surface or within the matrix of SLM-formed components. However, it is noteworthy that these pores can function as reservoirs for lubricants to enhance tribological performance in specific applications, such as porous bearings. In this study, the optimum conditions for fabricating Cu-15Ni-8Sn alloy porous bearings via SLM technology were investigated. By regulating laser power and hatch space during SLM processing, Cu-15Ni-8Sn alloy porous bearings were successfully obtained. The resulting oil bearings exhibited an oil content exceeding 18% and a radial crushing strength surpassing 370 MPa. At reduced laser power (80 W) and increased hatch spacing (0.9 mm), average friction coefficients of 0.1 and 0.13 were observed, with volumetric wear values of 10.3 mm³ and 96.7 mm³, respectively. The friction mechanism is a combination of abrasive wear and delamination wear. Full article