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Enhancement of the surface properties of selective laser melted maraging steel by large pulsed electron-beam irradiation
摘要： The present work aimed to decrease the surface roughness of maraging steel (MS) by selective laser melting (SLM) using large pulsed electron-beam (LPEB) irradiation as a post-treatment. The MS samples were fabricated using different combinations of laser power, scanning speed, hatch distance, and build angle. The morphological features, surface roughness, phase content, and corrosion resistance of the MS samples in their as-fabricated (ASF) state were compared after LPEB irradiation. The ASF SLM-MS samples exhibit the presence of partially melted particles that spread over the entire surface and many cracks in both the longitudinal and transverse directions. A higher arithmetical mean height (Sa: 2-17 μm), large variations in Sa measured at various locations, and a strong dependence of Sa on build angle were also observed. Post-treatment by LPEB irradiation removed the partially melted particles, while reflow of the molten mass filled the cracks and voids and facilitated the formation of a uniform surface with a bright metallic finish. This has resulted in a significant decrease in Sa (0.50-4.50 μm) and a smaller variation in Sa measured at different locations. Body-centered cubic α-martensite was the predominant phase for the ASF SLM-MS samples, along with a small fraction face-centered cubic γ-austenite phase. After LPEB irradiation, the martensite was reverted to the austenite phase. The corrosion resistance of the LPEB-irradiated samples was moderately better than that of the ASF SLM-MS samples. The uniform surface morphology, removal of partially melted particles, absence of pores and cracks, decrease in Sa, and moderate improvement in corrosion resistance suggests that LPEB irradiation can be used as a post-treatment for SLM-MS samples.
关键词： corrosion resistance,large pulse electron beam irradiation,maraging steel,Selective laser melting,surface roughness
更新于2025-09-23 15:19:57
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Direct Metal Laser Sintering of Maraging Steel: Effect of Building Orientation on Surface Roughness and Microhardness
摘要： Direct Metal Laser Sintering (DMLS) is a powder bed fusion based Additive Manufacturing (AM) process in which a part is fabricated using layer by layer deposition. In this work, 18% Ni Maraging steel 300 was fabricated using DMLS to examine the variations in surface finish and microhardness using three building orientations i.e. 0?, 45? and 90?. Surface roughness was found to decrease after 20 mm for 45? and 90?. Correspondingly, microhardness was found to decrease in the building direction. Understanding the effect of building orientation on the surface finish and hardness will allow the producer to fabricate superior quality AM parts with desired properties.
关键词： Direct Metal Laser Sintering,Microhardness,Additive Manufacturing,Surface finish,Maraging Steel
更新于2025-09-11 14:15:04
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Influence of heat treatment under hot isostatic pressing (HIP) on microstructure of intermetallic-reinforced tool steel manufactured by laser powder bed fusion
摘要： Microstructure and properties of as-built laser powder bed fusion (LPBF) steels differ from the conventional ones, and they may contain some porosity and lack of fusion. Therefore, post-treatments, including hot isostatic pressing (HIP), are used to densify the material, and tailor the properties of the final product. Usually, HIP is performed as an operation separate from heat treatment. In the present investigation a new approach was used, in which the whole cycle of the heat treatment was carried out in HIP under pressure, and the influence of HIP on microstructure of an advanced stainless maraging tool steel manufactured by LPBF was investigated. For a comparison, a conventional steel grade of the same chemical composition, after a heat treatment at the same temperature-time conditions, was also characterized. The microstructure of the steel was investigated by means of advanced microscopy and atom probe tomography. The influence of the manufacturing route, heat treatment and HIP on microstructure, austenitic phase fraction and size distribution of precipitates was investigated, and the role of high pressure in stabilization of austenite in the microstructure was discussed. It was concluded that since HIP influences phase transformations, a fundamental understanding of the influence of HIP on microstructure is necessary, and development of new post processing regimes guaranteeing the best performance of the material is required.
关键词： Hot isostatic pressing (HIP),Atom probe tomography,Transmission electron microscopy,Maraging steel,Precipitation hardening,Laser powder bed fusion
更新于2025-09-11 14:15:04