Effect of heat treatment on microstructure and mechanical characteristics of 316L stainless steel parts fabricated by hybrid additive and subtractive process

The effect of solution heat treatment on the mechanical and microstructural properties of 316L stainless steel parts fabricated through hybrid additive and subtractive process (HASP) is explored. These techniques synergistically combine additive manufacturing directed energy deposition (DED) with subtractive manufacturing (SM) technique in a single machine, and they provide an important opportunity to improve material utilization, part complexity and quality management in functional components. Thin-wall specimens were manufactured by HASP to investigate the effect of the solution heat treatment at different temperatures and different holding times on the microstructure and the resultant mechanical properties, such as the Vickers micro-hardness and tensile property. The results show that the content of δ and σ phases can be optimized via heat treatment. While the solution treatment temperature and time increase, the content of the σ and δ phases in the γ matrix can distinctly decrease, which causes the strength to degrade but the ductility to increase. These results suggest that the microstructure and the resulting mechanical properties of HASP-fabricated samples can be adjusted through the adjustment of solution heat treatment.