Search Results (104)

To capture the complex metallic spatter and melt pool behavior during the rapid interaction between the laser and metal material, high-speed cameras are applied to record the laser powder bed fusion process and generate a large volume of image data. In this study, four deep learning algorithms are applied: YOLOv5, Fast R-CNN, RetinaNet, and EfficientDet. They are trained by the recorded videos to learn and extract information on spatter and melt pool behavior during the laser powder bed fusion process. The well-trained models achieved high accuracy and low loss, demonstrating strong capability in accurately detecting and tracking spatter and melt pool dynamics. A stability index is proposed and calculated based on the melt pool length change rate. Greater index value reflects a more stable melt pool. We found that more spatters were detected for the unstable melt pool, while fewer spatters were found for the stable melt pool. The spatter’s size can affect its initial ejection speed, and large spatters are ejected slowly while small spatters are ejected rapidly. In addition, more than 58% of detected spatters have their initial ejection angle in the range of 60–120$°$. These findings provide a better understanding of spatter and melt pool dynamics and behavior, uncover the influence of melt pool stability on spatter formation, and demonstrate the correlation between the spatter size and its initial ejection speed. This work will contribute to the extraction of important information from high-speed recorded videos for additive manufacturing to reduce waste, lower cost, enhance part quality, and increase process reliability. Full article

Laser-based powder bed fusion of metals (PBF-LB/M) is one of the most promising additive manufacturing technologies to fabricate complex-structured metal parts. However, its corresponding applications have been limited by technical bottlenecks and increasingly strict industrial requirements. Process optimization, a scientific issue, urgently needs to be solved. In this paper, a three-phase transient model based on the level-set method is established to examine the heat transfer and melt pool behavior in PBF-LB/M. Surface tension, the Marangoni effect, and recoil pressure are implemented in the model, and evaporation-induced mass and thermal loss are fully considered in the computing element. The results show that the surface roughness and density of metal parts induced by heat transfer and melt pool behavior are closely related to process parameters such as laser power, layer thickness, scanning speed, etc. When the volumetric energy density is low, the insufficient fusion of metal particles leads to pore defects. When the line energy density is high, the melt track is smooth with low porosity, resulting in the high density of the products. Additionally, the partial melting of powder particles at the beginning and end of the melting track usually contributes to pore formation. These findings provide valuable insights for improving the quality and reliability of metal additive manufacturing. Full article

Laser powder-bed fusion (L-PBF) additive manufacturing has been widely explored for fabricating intricate metallic parts such as lattice structures with thin struts. However, L-PBF-fabricated small parts (e.g., thin struts) exhibit different morphological and mechanical characteristics compared to bulk-sized parts due to distinct scan lengths, affecting the melt pool behavior between transient and quasi-steady states. This study investigates the keyhole porosity in Ti6Al4V thin struts fabricated by L-PBF, incorporating a range of strut sizes, along with various levels of linear energy densities. Micro-scaled computed tomography and image analysis were employed for porosity measurements and evaluations. Generally, keyhole porosity lessens with decreasing energy density, though with varying patterns across a higher energy density range. Keyhole porosity in struts predictably becomes severe at high laser powers and/or low scan speeds. However, a major finding reveals that the porosity is reduced with decreasing strut size (if less than 1.25 mm diameter), plausibly because the keyhole formed has not reached a stable state to produce pores in a permanent way. This implies that a higher linear energy density, greater than commonly formulated in making bulk components, could be utilized in making small-scale features to ensure not only full melting but also minimum keyhole porosity. Full article

The present study aims to investigate the microstructural evolution and local mechanical properties of an AlFe18Si8Cr5Ni2 alloy processed via Powder Bed Fusion–Laser-Based Manufacturing (PBF-LB/M). Designed with a focus on sustainability, this alloy was produced by deriving the necessary elements from AlSi10Mg and 304L steel, two of the most widely used alloys and, consequently, among the easiest materials to source from machining scrap. By leveraging iron, chromium, and nickel from these widespread standard compositions, the alloy mitigates the detrimental effects of Fe contamination in Al-based alloys while simultaneously enhancing mechanical performance. A comprehensive investigation of the impact of rapid solidification and thermal cycling offered novel insights into phase stability, elemental distribution, and local mechanical behavior. In particular, microstructural analyses using scanning electron microscopy (SEM), field emission SEM, energy-dispersive X-ray spectroscopy, X-ray diffraction, and differential scanning calorimetry revealed significant phase modifications post PBF-LB/M processing, including Fe-rich acicular phase segregation at melt pool boundaries and enhanced strengthening phase formation. In addition, nanoindentation mapping was used to demonstrate the correlation between microstructural heterogeneity and local mechanical properties. The findings contribute to a deeper understanding of Al-Fe-Si-Cr-Ni alloy changes after the interaction with the laser, supporting the development of high-performance, sustainable Al-based materials for PBF-LB/M applications. Full article

Laser-Directed Energy Deposition (LDED) has recently been widely used for 3D-printing metal components and repairing high-value parts. One key performance indicator of the LDED process is represented by melt pool stability and spatter behavior. In this research study, an off-axis vision monitoring system is employed to characterize spatter formation based on different anomalies in the process. This study utilizes a 1 kW fiber laser-based LDED system equipped with a monochrome high-dynamic-range (HDR) vision camera and an SP700 Near-IR/UV Block visible bandpass filter positioned at various locations. To extract meaningful features from the original images, a novel image processing algorithm is developed to quantify spatter counts, orientation, area, and distance from the melt pool under harsh conditions. Additionally, this study analyzes the average number of spatters for different laser power settings, revealing a strong positive correlation. Validation experiments confirm over 93% detection accuracy, underscoring the robustness of the image processing pipeline. Furthermore, spatter detection is employed to assess the impact of spatter formation on deposition continuity. This research study provides a method for detecting spatters, correlating them with LDED process parameters, and predicting deposit quality. Full article

The combustion behavior and thermal performance of industrial-scale borax pentahydrate (Na₂B₄O₇·5H₂O) melting furnaces remain underexplored despite their critical role in boric oxide (B₂O₃) production, a key input for high-performance manufacturing. This study addressed this gap by employing three-dimensional computational fluid dynamics (CFD) simulations to model two operational natural gas-fired furnaces with distinct burner configurations (four-burner and six-burner systems). The analysis focused on optimizing burner placement, specifically, the axial distance and inclination angle, to enhance thermal uniformity and reduce refractory wall damage caused by aggressive high-temperature borate corrosion. A comprehensive parametric study of twelve burner configurations revealed that tilting the burners at 5–10° significantly improved temperature uniformity while reducing peak wall temperatures and mitigating localized hot spots. The optimal design, incorporating a 10° burner angle and a staggered burner arrangement (Case 11), attained a melt pool temperature of 1831.3 K and a charging average wall temperature of 1812.0 K. These values represent essential benchmarks for maximizing furnace efficiency and operational stability. The modified designs for the four- and six-burner systems led to improved temperature distributions and a notable reduction in maximum wall temperatures, directly contributing to longer maintenance intervals and improved refractory durability. The findings of this study confirm that minor geometrical and angular adjustments in burner placement can yield significant performance gains. The validated CFD approach and proposed design modifications offer a scalable, low-cost strategy for improving combustion efficiency and furnace lifespan in borax processing facilities. Full article

Titanium alloys are increasingly used in aeronautical applications, a sector that requires highly controlled materials. In particular, inclusion cleanliness is a necessary and mandatory condition for safe use in aeronautical components. During the production and processing of titanium alloys, inclusions are likely to appear, in particular high-density inclusions (HDIs) originate from refractory metals such as molybdenum or tungsten carbide. Plasma Arc Melting–Cold Hearth Remelting (PAMCHR) is one of the most effective recycling and refining process for titanium alloys. Firstly, this work reports the thermal modeling of the melting of raw materials in the melting crucible and a complete 3D numerical simulation of the thermo-hydrodynamic behavior of the metal flow in the PAMCHR furnace, based on the software Ansys-Fluent CFD V21.1. Simulation results are presented for a 100 kg/h melting test performed in a pilot furnace with a comparison between the measured and calculated pool profiles and residence time distributions that show satisfactory agreements. Additionally, a Lagrangian calculation of particle trajectories in the liquid metal pool is also performed and insemination of HDIs in the pilot furnace has been tested. Both numerical and experimental tests demonstrate the inclusion removal in the melting crucible. Full article

Additive Manufacturing (AM) processes, particularly PBF-LB/M, are considered advantageous due to their flexibility, which allows process engineers to design and fabricate intricate structures both in the prototyping and component manufacturing phases. It is well known that the behavior of the process directly impacts the quality of the materials and thereby induces inhomogeneities on the powder bed on the building platform. Several parameters can be tuned to keep the process under control, getting rid of process uncertainty and distinguishing aspects of a specific machine model. Such behavior requires an extended analysis of the powder bed inhomogeneities and the definition of limits in the printing process. In this work, carried out on Alloy 718 specimens printed using an EOS M290 machine, the inhomogeneities of the melt pool stability, density, and material properties were investigated based on three main factors: the amount of area melted or fused, the gas flow speed setpoint, and the location on the building platform. The test results for Track Stability, melt-pool shape, and porosity analysis show that criticality occurs when more than 50% of the building platform is exposed. This can be partly fixed by raising the differential pressure value. Full article

Laser additive manufacturing (AM) technology has become an important method for the manufacturing of high-performance aluminum alloy parts. However, the thermal effect of the molten pool and the defect formation mechanism are still the key issues restricting forming quality. To address this issue, this paper systematically investigates the effects of key parameters such as laser power and pulse frequency on the thermal conductivity, kinetic behavior, and defect control of the molten pool through multi-physics coupled numerical simulation to provide theoretical support for improving the quality of components. It is found that the laser power and pulse frequency play a key role in the molten pool morphology and defect generation, with too low a power leading to non-fusion and too high a power triggering overheating and cracking, and too low a frequency leading to unstable morphology and too high a frequency triggering grain coarsening and thermal stress cracking. The optimized process parameters (power 700–800 W, frequency 72–100 KHz) effectively improved the melt pool morphology and reduced the defects. This study reveals the intrinsic mechanism of melt pool dynamics and defect formation, which provides important instructions for optimizing the aluminum alloy additive manufacturing process. Full article

In the laser powder bed fusion (LPBF) process, the surface quality of intermediate layers impacts interlayer bonding and part forming quality. Due to the complex dynamic process inherent in LPBF, current monitoring methods struggle to achieve high-quality in situ online monitoring, which limits the in-depth understanding of the evolution mechanisms of the surface morphology of LPBF intermediate layers. This paper employs an optimized coaxial optical imaging method to monitor key LPBF processes and analyzes the intermediate layer surface morphology evolution mechanism considering heat, force, and mass transfer. Results indicate that LPBF intermediate layer surfaces are influenced by energy density, melt pool behavior, and previous layer morphology, forming complex topological structures. At a low energy density, insufficient powder melting causes balling, extended by subsequent melt pools to form a reticulated structure and local large-scale protrusions. Heat accumulation at a high energy density promotes melt pool expansion, reduces melt track overlap, and effectively eliminates defects from previous layers via remelting, with spatter becoming the main defect. Additionally, the melt pool wettability on the part contours captures external powder, forming unique, overhanging contour protrusions. This paper enhances understanding of LPBF intermediate layer surface morphology formation mechanisms and provides a theoretical basis for optimizing surface quality. Full article

Cemented carbides, renowned for their exceptional strength, hardness, elastic modulus, wear resistance, corrosion resistance, low coefficient of thermal expansion, and chemical stability, have long been indispensable tooling materials in metal cutting, oil drilling, and engineering excavation. The advent of additive manufacturing (AM), commonly known as “3D printing”, has sparked considerable interest in the processing of cemented carbides. Among the various AM techniques, Selective Laser Melting (SLM), Selective Laser Sintering (SLS), Selective Electron Beam Melting (SEBM), and Binder Jetting Additive Manufacturing (BJAM) have garnered frequent attention. Despite the great application potential of AM, no single AM technique has been universally adopted for the large-scale production of cemented carbides yet. The SLM and SEBM processes confront substantial challenges, such as a non-uniform sintering temperature field, which often result in uneven sintering and frequent post-solidification cracking. SLS notably struggles with achieving a high relative density of carbides. While BJAM yields WC-Co samples with a lower incidence of cracking, it is not without flaws, including abnormal WC grain growth, coarse WC clustering, Co-rich pool formation, and porosity. Three-dimensional gel-printing, though possessing certain advantages from its sintering performance, falls short in dimensional and geometric precision control, as well as fabrication efficiency. Cemented carbides produced via AM processes have yet to match the quality of their traditionally prepared counterparts. To date, the specific densification and microstructure evolution mechanisms during the AM process, and their interrelationship with the feedstock carbide material design, printing/sintering process, and resulting mechanical behavior, have not been thoroughly investigated. This gap in our knowledge impedes the rapid advancement of AM for carbide processing. This article offers a succinct overview of additive manufacturing of cemented carbides, complemented by an analysis of the current research landscape. It highlights the benefits and inherent challenges of these techniques, aiming to provide clarity on the present state of the AM processing of cemented carbides and to offer insights into potential future research directions and technological advancements. Full article

The ultrasonic vibration laser cladding method is a material-saving and green method to fabricate super abrasive structured grinding wheels. However, the mechanism of the ultrasonic vibration’s effect on the movement behavior of abrasive grains in the laser cladding process has not been clarified. To address this, the impacts of ultrasonic vibration on the abrasive grain distribution and movement behavior were experimentally studied, and the numerical simulation method was introduced to simulate the ultrasonic vibration laser cladding process. A two-dimensional Gaussian cross-section heat source model was developed, and its energy density conformed to a Gaussian distribution in both space and time. The simulations of the temperature and fluid fields of the melt pool were carried out. The CBN abrasive grains in the melt pool were subjected to gravity, the buoyancy force, the drag force of the metal fluid, and the sonophoretic radiation force of the ultrasonic vibration. Based on them, the effects of ultrasonic vibration on the movement behaviors and trajectories of the CBN abrasive grains were analyzed. The influence of the ultrasonic amplitude on the distribution of abrasive grains was studied. The simulation results revealed that the abrasive grains could be uniformly distributed on the surface of the cladding layer during the ultrasonic vibration laser cladding process. Full article

This study explores the effect of heat treatment on the microstructural characteristics and corrosion resistance of 316L stainless steels (SSs) produced via laser powder bed fusion (L-PBF), focusing on anisotropic corrosion behavior—a relatively less explored phenomenon in LPBF 316L SSs. By systematically analyzing the effects of varying heat treatment temperatures (500 °C, 750 °C, and 1000 °C), this work uncovers critical correlations between microstructural evolution and corrosion properties. The findings include the identification of anisotropic corrosion resistance between horizontal (XY) and vertical (XZ) planes, with the vertical plane demonstrating higher pitting and repassivation potentials but greater post-repassivation current densities. Furthermore, this study highlights reductions in grain size, dislocation density, and melt pool boundaries with increasing heat treatment temperatures, which collectively diminishes corrosion resistance. These insights advance the understanding of processing–structure–property relationships in additively manufactured metals, providing practical guidelines for optimizing thermal post-processing to enhance material performance in corrosive environments. Full article

In this study, the melt pool formation behavior of high-speed laser-arc hybrid welding of aluminum plates was simulated using finite element analysis (FEA). To evaluate the heat input efficiencies of the laser and arc, standalone laser or arc welding experiments were conducted using the same arc or laser processing parameters as those employed in hybrid welding. These experiments were also simulated using FEA to calibrate the laser and arc heat adsorption parameters. The melt pool shapes were measured from cross-sectional optical microscope (OM) images of the specimens and subsequently used to develop a thermal analysis simulation of the laser and arc welding processes. A simulation model for the laser-arc hybrid welding process was developed by combining the heat input models of the laser and arc welding processes. The FEA model successfully predicted the melt pool shapes observed in the experiments. The accuracy of the developed model was evaluated, yielding average errors in the melt pool sizes of the laser, arc, and hybrid welds of 5.43%, 6.89%, and 4.51%, respectively. Full article

Crack-free Stellite-6 alloy was fabricated using the laser powder bed fusion technique equipped with a heating module as the first attempt. Single tracks were printed with a build plate heated to 400 °C to identify the processing window. Based on the melt pool dimensions, two combinations (sample A: 300 W/750 mm/s and sample B: 275 W/1000 mm/s) were identified to print the cubes. The as-printed microstructure comprised FCC-Co dendrites with M₇C₃ in the interdendritic region. W-rich M₆C particles were found in the overlapping regions between the melt pools, matching the Scheil simulations. However, gas pores were observed due to the higher nitrogen and oxygen content of the feedstock requiring hot isostatic pressing (HIP) at 1250 °C and 150 MPa for 2 h. Sample A was partially recrystallized with slightly coarsened M₇C₃, while sample B underwent complete recrystallization followed by grain growth along with higher coarsening of the M₇C₃ after HIP. The varying recrystallization behavior can be attributed to the difference in residual stresses and grain aspect ratio in the as-built condition dictated by laser power and scanning speed. The microhardness after HIP was slightly higher than its wrought counterpart, indicating no severe impact of post-processing on the properties of Stellite-6 alloy. Full article