Powder Bed Research Articles (Page 1)

Abstract Additively processed materials are increasingly used to manufacture customized parts, e.g. medical implants. Implant surfaces often require a smooth finish, which can be achieved by post-processing and well-defined process parameters. In this study, the effects of electropolishing of metal parts produced by laser powder bed fusion are investigated using Hull cell experiments and a three-electrode setup. Current density voltage curves were measured with the three-electrode setup to identify the regimes for electropolishing. Subsequently different constant currents were applied and Hull cell experiments were conducted. The surface roughness (Sz, Sa) and the mass removal were analysed. Surface morphologies were assessed using laser scanning and scanning electron microscopy. A reduction of the initial surface roughness of more than 90% to Sa < 0.3 µm has been achieved. Considering the passed electrical charge during electropolishing, results from Hull cell experiments are systematically correlated with current-controlled electropolishing. This approach enables the precise tailoring of polishing parameters to achieve surfaces with defined roughness. Furthermore, the study demonstrates the suitability of Hull cells in determining electropolishing parameters for additive materials and highlights their contribution to post-processing in additive manufacturing.

Laser powder bed fusion (L-PBF) is an additive manufacturing technique that enables the fabrication of complex geometries through a layer-by-layer approach, overcoming limitations of conventional manufacturing. In this study, multiaxial low-cycle fatigue (MLCF) tests were conducted on L-PBF Ti-6Al-4V (Ti64) specimens built in four different orientations, selected based on critical plane orientations identified from rolled titanium. Under proportional strain-controlled loading, the cyclic softening behavior, mean stress response, and fracture mechanisms of the material were systematically investigated. The results show that L-PBF Ti64 exhibits a three-stage softening characteristic (continuous softening, stable, and rapid softening). Fatigue cracks primarily initiate from inner-surface lack-of-fusion defects. Crack propagation shows cleavage and quasi-cleavage characteristics with tearing ridges, river patterns, and multi-directional striations. Proposed KBMP life prediction model, incorporating λ and building direction parameters, was developed. The KBMP-λ model demonstrates optimal accuracy, providing a reliable tool for the design of L-PBF titanium components subjected to complex multiaxial fatigue loading with relative errors within 20%.

Abstract Recent advancements in the additive manufacturing (AM) of magnetic materials has opened the possibility of producing tailored functional gradients, which can offer significant potential in the creation of components with changing hard magnetic properties across different regions. In this study, an Fe–Cr–Co base alloy was produced by laser powder bed fusion (LPBF) and then modified with in-situ alloying. incorporating increasing concentrations of an alloying element that either enhances or diminishes the hard magnetic properties. We investigated the chemical composition and the morphology of the boundary layer between regions, as well as the corresponding magnetic properties in each region. Boundary layer thickness was found to be independent of the printing process, and post processing conditions and VSM measurements reveal distinct variations in the magnetic properties across the chemical gradient, highlighting the impact of alloying concentration on the hard magnetic performance. Finally, an anisotropic behaviour of the magnetic properties was observed in the base alloy which changes as a function of the aluminum content. These findings contribute valuable insights into the design and fabrication of functionally graduated materials via LPBF, with potential applications in advanced magnetic devices and components requiring materials with spatially tailored magnetic properties.

Abstract Laser powder bed fusion (LPBF) is a metal additive manufacturing process that uses a high-power laser to melt a predefined shape in a bed of metal powder, layer by layer. The size of the melted pool throughout the process can significantly affect the mechanical properties of the final part; too small of a melt pool may result in poor fusion, too large will cause porosity. The size of the melt pool is governed by inherently complex multiphysical interactions. Complex models have been developed and simplified in the literature, and in this paper, a nonlinear first-order single state energy transfer model is used to simulate the size of the melt pool transverse surface area. The error is defined as the difference between the melt pool area and a desirable reference value, and a sliding mode control (SMC) law is developed to use input laser power to drive the system to a zero-error manifold in finite time. Since the model used takes advantage of potentially unrealistic geometrical assumptions about the melt-pool shape, the control law is further developed to be robust to inaccuracies and real-time changes in the system parameters related to this assumption. The performance of the controller is compared with other control strategies in the presence of bounded parameter uncertainty.

Among nickel-based superalloys, Inconel® 725 (IN725) stands out for its excellent strength and corrosion resistance. Despite this, its application in additive manufacturing remains largely unexplored. This study investigates laser powder bed fusion of metals (PBF-LB/M) applied to IN725 powder derived from recycled industrial waste, addressing sustainability and process optimization goals. Using the design of experiments approach, the laser power–scan speed process parameter space was explored. Gaussian process regression models were developed to predict surface roughness, relative density, and microhardness. Both direct process parameters and volumetric energy density were evaluated as model inputs to assess predictive performance. The findings established a broad optimal process window for manufacturing high-quality IN725 parts using PBF-LB/M. Specifically, an optimal combination of 99.99% relative density, 7.3 μm roughness, and 311 HV microhardness was achieved by processing the powder at 250 W and 1,500 mm/s. By demonstrating the feasibility of using recycled IN725 powder, this study contributes to the development of sustainable manufacturing practices and supports wider adoption of PBF-LB/M in oil and gas, marine, and chemical processing industries, where IN725 is widely employed.

ABSTRACT Laser powder bed fusion (L‐PBF) has emerged as a complementary additive manufacturing (AM) technology and is capable of producing high‐resolution geometrically complex metal components. This review first highlights the role of minor copper (Cu) additions in refining microstructures and enhancing mechanical strength, corrosion resistance, and antibacterial performance in widely studied metallic alloys fabricated via L‐PBF, thus showcasing the multifunctional benefits of Cu addition. So far, processing of Cu and its alloys via L‐PBF remains challenging due to the high reflectivity and thermal conductivity of Cu, which reduce laser–powder interaction efficiency. Recent advances in laser source technology, powder surface modification, alloy design, in situ alloying, process optimization, and post‐heat treatments have significantly improved the printability and functional performance of Cu‐based materials. This review summarizes the advances in L‐PBF of Cu and its alloys/composites, emphasizing powder characteristics, laser absorptivity, melt pool stability, defect formation, and microstructural evolution. It also critically evaluates elevated‐temperature mechanical/thermal stability and anisotropy in mechanical, electrical, and thermal performance, and outlines future research directions and industrial prospects.

This study investigates the mechanical behavior and deformation characteristics of Inconel 718 lattice structures with different unit cell sizes fabricated by laser powder bed fusion (LPBF). Two body-centered cubic (BCC) lattice structures with unit cell sizes of 2 mm (BCC 2) and 4 mm (BCC 4) were designed while maintaining a constant strut diameter. The measured relative densities were 31.48% for BCC 2 and 8.67% for BCC 4, indicating a significant reduction in density as the lattice size increased. Although the relative densities differed considerably, both lattices exhibited similar microstructural features such as columnar grains, melt pool boundaries, and surface-attached partially melted powders. No distinct thermal influence was observed with varying unit cell size, demonstrating that uniform build quality was maintained regardless of geometric scale under the given LPBF conditions. Compressive testing revealed that BCC 2 exhibited substantially higher compressive strength (58.47±3.23 MPa) than BCC 4 (1.78±0.11 MPa), which was attributed to enhanced structural stability and a higher number of struts and nodes. Digital Image Correlation (DIC) analysis and cross-sectional microstructure observations confirmed that BCC 2 displayed progressive densification and buckling-dominated deformation, while BCC 4 predominantly exhibited bending-dominated failure with localized deformation. Notably, despite the narrower strut spacing in BCC 2, no discernible thermal influence—such as melt pool distortion or grain coarsening—was identified, indicating that the effect of unit cell size on thermal behavior during LPBF processing remained negligible under the given conditions. These findings were discussed in terms of the effects of lattice unit cell size on microstructure, compressive properties, and deformation behavior.

Additive manufacturing (AM), particularly laser-based powder bed fusion (PBF-LB), enables the production of high-strength, lightweight components made of aluminum alloys such as AlSi10Mg. However, joining these parts via welding remains a significant challenge due to weld seam porosity caused by hydrogen entrapment. This study investigated the influence of the PBF-LB process parameters, tungsten inert gas (TIG) welding settings, filler material, and post-weld T6 heat treatment on the tensile strength and porosity of welded AlSi10Mg components. Using two different layer heights (30 µm and 60 µm), plate thicknesses (3 mm and 5 mm), and varying welding conditions, a series of 10 TIG-welded sample groups were fabricated and analyzed. Microstructural, hardness, porosity, and tensile tests revealed that porosity was high across all samples (11–19%). A subsequent T6 heat treatment improved the tensile strength. Higher layer heights and thinner plates led to a higher tensile strength of the weld seam, while the addition of a filler material showed limited benefits. No other influencing factors or interactions could be found. The results emphasize the need to optimize hydrogen control in the processes, melt pool dynamics, and weld seam geometry to receive reliable joints in lightweight manufacturing of PBF-LB AlSi10Mg parts.

Abstract In the present study a metastable austenitic stainless steel X2CrMnNi16-7–4.5 was investigated. The alloy composition was adjusted by mixing steel powder X2CrMnNi16-7–9 and steel powder X2CrMnNi16-7–3, whereby the first steel exhibits a primary-austenitic and the latter one a primary-ferritic solidification of the melt, in order to achieve a fine-grained, predominantly austenitic microstructure. After mixing of the powder blend the material was subsequently processed by in situ alloying during powder bed fusion electron beam melting (PBF-EB/M), using two different build parameter sets. The study demonstrates how powder blending and in situ alloying can be used to tailor microstructural features like grain size, texture and phase composition in PBF-EB/M processing by changing the chemical composition of an alloy. The microstructure and phase composition of manufactured specimens were examined by different techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD) and measurements of ferromagnetic phase content. The steel was predominantly austenitic and exhibited a fine-grained microstructure for one of the build parameter sets, with a slight < 011 > texture in build direction (BD) after the PBF-EB/M process. Mechanical properties of alloy X2CrMnNi16-7–4.5 were characterized by tensile as well as low cycle fatigue (LCF) tests. In tensile tests the material possesses excellent mechanical properties due to the occurrence of the TRIP (TRansformation-Induced Plasticity) effect under loading, whereby the orientation of the loading axis (LA) relative to the build direction plays a detrimental role. Fatigue tests revealed that surface polishing did not show any improvement in fatigue lifetime compared to the as-built specimens with a natural surface, which was attributed to the presence of numerous inclusions and lack of fusion (LOF) defects.

Ti65 high-temperature titanium alloy, known for its exceptional high-temperature mechanical properties and oxidation resistance, demonstrates considerable potential for aerospace applications. Nevertheless, conventional manufacturing techniques are often inadequate for achieving high design freedom and fabricating complex geometries. This study presents a systematic investigation into the process optimization, microstructure characterization, and mechanical performance of Ti65 alloy produced by laser powder bed fusion (LPBF). Via meticulously designed single-track, multi-track, and bulk sample experiments, the influences of laser power (P), scanning speed (V), and hatch spacing (h) on molten pool behavior, defect formation, microstructural evolution, and surface roughness were thoroughly examined. The results indicate that under optimized parameters, the specimens attain ultra-high dimensional accuracy, with a near-full density (>99.99%) and reduced surface roughness (Ra = 3.9 ± 1.3 μm). Inadequate energy input (low P or high V) led to lack-of-fusion defects, whereas excessive energy (high P or low V) resulted in keyhole porosity. Microstructural analysis revealed that the rapid solidification inherent to LPBF promotes the formation of fine acicular α′-phase (0.236–0.274 μm), while elevated laser power or reduced scanning speed facilitated the development of coarse lamellar α′-martensite (0.525–0.645 μm). Tensile tests demonstrated that samples produced under the optimized parameters exhibit high ultimate tensile strength (1489 ± 7.5 MPa), yield strength (1278 ± 5.2 MPa), and satisfactory elongation (5.7 ± 0.15%), alongside elevated microhardness (446.7 ± 1.7 HV0.2). The optimized microstructure thereby enables the simultaneous achievement of high density and superior mechanical properties. The fundamental mechanism is attributed to precise control over volumetric energy density, which governs melt pool mode, defect generation, and solidification kinetics, thereby tailoring the resultant microstructure. This study offers valuable insights into defect suppression, microstructure control, and process optimization for LPBF-fabricated Ti65 alloy, facilitating its application in high-temperature structural components.

Comparative Wear Behavior of Hot-Forged and Laser Powder Bed Fusion-Manufactured 18Ni300 Maraging Steel in Pre- and Post-processed Conditions

Ti-6Al-4V, a popular biomedical alloy, is increasingly fabricated by additive manufacturing methods, like laser powder bed fusion (LPBF). However, rapid thermal cycling and steep temperature gradients often induce mechanical degradation, corrosion, and wear. To address these challenges, laser surface modification is explored. This study investigates the microstructure and corrosion behaviour (simulated body fluid, 37 °C) of LPBF and wrought Ti-6Al-4V after laser surface melting (LSM) treatment. LSM produced modified layers of 1250–1350 µm (LPBF) and 1530–1600 µm (wrought), with gradients from remelted dendrites to acicular martensite. Microhardness in the layers increased to 655–680 HV due to lattice expansion, crystallite refinement, and higher dislocation density. However, LSM-treated alloys showed higher corrosion rates and weaker passive films, attributed to increased surface roughness, martensite formation, residual stresses, and microstructural inhomogeneity. Aluminium silicate surface films/residues further compromised passivity. Nevertheless, both LSM-LPBF and LSM-wrought specimens displayed low corrosion current densities (10−4 mA/cm2), true passivity (10−3–10−4 mA/cm2), and high resistance to localised corrosion. After cyclic polarisation, rutile-rich TiO2 surface films with aluminium silicate hydrates were observed. LSM-LPBF specimens showed slightly inferior general corrosion resistance compared to LSM-wrought counterparts, due to pronounced surface texture variations, phase/composition differences, higher microstrains and dislocation density.

The reversibility of shape memory alloys (SMAs) is crucial for superelastic applications. Although nanocrystalline structures improve superelasticity, achieving them in Cu–Al–Mn SMAs is difficult due to grain coarsening. Recent studies suggest nanoscale precipitates may enhance superelasticity without grain refinement. Here, nanoscale precipitates into laser powder bed fusion (L‐PBFed) Cu–Al–Mn alloys are introduced via aging to investigate their effects on phase transformation and superelasticity. Combining Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD)‐based phase diagram calculations with in situ X‐ray diffraction (XRD), two precipitates (α′ and γ) are identified as potential strengthening precipitates. With the help of nanoindentation test, γ precipitate is selected as the optimal strengthening phase due to its high hardness. Electron backscattered diffraction (EBSD) reveals a {0001} γ //{110} Aus orientation relationship and interfacial dislocation segregation between γ and austenite. Resistivity tests show lost thermal martensitic transformation in (austenite + γ) structure, but stress‐field cooling confirms stress‐induced martensitic transformation (SIMT) via negative thermal expansion. After aging at 250 °C for 180 min, tensile test shows linear superelasticity with enhanced modulus (66.7 GPa), reduced hysteresis‐to‐input energy ratio (4.4%) and full recovery (≈100%). These findings suggest that γ precipitate can enhance the superelasticity of Cu–Al–Mn SMAs, providing a new enhancing strategy.

Tribological behavior of nanostructured AlSi10Mg fabricated by laser powder bed fusion/high-pressure torsion hybrid

In-situ detection of powder bed defects in laser powder bed fusion using 3D surface normals and depth mapping

Linkage between process-induced microstructure and magnetic property of Nd-Fe-B permanent magnets additively manufactured by laser powder bed fusion

On the high-temperature tensile deformation mechanisms of the IN738LC superalloy fabricated by laser powder bed fusion

B2 phase controlling method of austenitic Fe–16Mn–10Al–5Ni–0.86C lightweight steel using laser powder bed fusion process and its microstructure and mechanical properties

Numerical and experimental study on homogenized heat transfer performance of periodic gyroid-based heat exchangers manufactured through Laser Powder Bed Fusion in pure copper, aluminum A205 alloy, and reaction bonded silicon carbide

High-precision laser powder bed fusion of 316L stainless steel and its SiC reinforcement composite materials