Numerical and experimental investigation of laser remelting in selective laser melting of 316L stainless steel

Selective laser melting (SLM) has a wide application potential as a near-net-shape manufacturing process, but with the increasing quality requirements of additive manufactured parts in various industries, high demands are placed on the manufacturing quality, density uniformity and microstructure of additive manufactured parts. In this regard, this study adopts laser remelting (LR) to improve the manufacturing quality, microstructure and mechanical properties of 316 L stainless steel (316LSS) metal samples manufactured by SLM. The influencing mechanisms of the temperature and velocity fields on the manufacturing quality during the LR process are systematically revealed via numerical simulation. The results indicate that in the region of low laser energy density, the wettability and fluidity of remelted materials are poor, which will deteriorate the manufacturing quality. In contrast, high energy density enables sufficient melting of remelted materials, accompanied by uniform and stable melt-pool flow, favorable interlayer metallurgical bonding, and reduced porosity. Moreover, the LR process achieves effective grain refinement and reduces the fraction of low‑angle grain boundaries, thereby improving both hardness and tensile performance of the specimens. In particular, the optimal comprehensive manufacturing quality is obtained at the laser remelting energy density of 87.72 J/mm³ .