Influence of substrate temperature on microstructural and mechanical properties of 316L stainless steel consolidated by laser powder bed fusion

Abstract

This study investigates the microstructure and mechanical properties of 316L stainless steel (316LSS) samples fabricated by additive manufacturing (AM), in order to optimise the process for improving the properties of 316LSS parts built by laser powder bed fusion (LPBF). Accordingly, a substrate heating was performed on an SLM 280HL printer fitted with an experimental heating device. During the process, samples are built on a substrate heated up to 600 ∘C. The substrate temperature significantly influences the microstructural evolution and mechanical properties of manufactured parts. Concerning tensile properties, the ultimate tensile strength (UTS) and yield strength (YS) decrease as a function of the substrate temperature whereas the elongation (El) increases as a function of the substrate temperature. These results are similar to those obtained with a post-heat treatment performed on parts manufactured by forging or LPBF. The tensile and impact energies reach values higher than the minimum requirement for 316LSS manufactured by forging, according to the RCC-MRx code used for materials dedicated to French nuclear applications. When the substrate temperature is equal to 350 ∘C, the UTS, YS, El and impact energy reached 596 ± 5 MPa, 489 ± 3 MPa, 48 ± 3% and 123 ± 20 J, respectively. Finally, this study demonstrates that heating the substrate during the process is a promising solution to optimise the fabrication route by suppressing post-process heat treatment of 316LSS made by LPBF.