High Temperature Heat Treatment and Severe Shot Peening of PBF-LB Manufactured 316L Stainless Steel

Abstract

Laser powder bed fusion manufactured (PBF-LB) austenitic stainless steel 316L offers higher strength than traditionally manufactured counterparts. Further improvement can be obtained with suitable surface modification. This work focuses on improving the material qualities with the aid of severe shot peening (SSP), which can increase the surface hardness, reduce roughness and produce grain refinement and compressive residual stresses on the surface. These qualities are all beneficial for the fatigue life of the material. Material was studied in two conditions: as built and heat treated (HT) at 1100 °C and the effect of SSP on both. The results showed clear microstructural changes on both structures leading to increased strength. The fatigue strength of as built material benefits greatly from the SSP treatment, but when performed on a high temperature HT material the benefits are negligible. However, in applications where the parts are subjected to bending forces the surface modification plays a role also with the HT material.