Influence of in situ heating and laser remelting on martensitic precipitation-hardening stainless steel fabricated by laser powder bed fusion

Abstract The introduction of in situ heat-assisted fabrication and laser remelting as novel techniques within laser-based additive manufacturing aims to mitigate porosity and reduce surface roughness. However, a comprehensive understanding of the impact of in situ heating and laser remelting on mechanical properties and microstructure is still lacking, particularly for precipitate-hardenable metals like 15-5PH and 17-4 PH stainless steel, which can yield mechanical properties comparable to conventionally fabricated materials. This study presents experimental findings that demonstrate the efficacy of in situ heating during laser powder bed fusion (LPBF) in significantly reducing porosity and enhancing the material’s ductility. The performed XRD analyses indicate that the retained austenite phase increased in samples fabricated with heat-assisted LPBF. There is a reduction in the experimentally measured ultimate tensile strength, yield strength, and hardness in the precipitate-hardenable stainless steel samples that were fabricated by the introduced method using a heated plate. The experimental results reveal a 25% increase in ductility for heat-assisted LPBF fabrication compared to without heated substrate. In addition, SEM fractography analysis indicates a significant reduction in crack size and porosity in samples produced by heat-assisted LPBF.