Comparative study of additively manufactured and reference 316 L stainless steel samples – Effect of severe shot peening on microstructure and residual stresses

Abstract

The as-built selective laser melted (SLM) austenitic stainless steel 316 L components are characterized by presence of quality related concerns such as tensile residual stresses, poor surface finish, etc. These issues may prove to be detrimental during the actual usage of components and could result in poor mechanical performance. Therefore, it is important to perform the apt post processing such as heat treatment and shot peening to tailor such problems and facilitate improved mechanical performance. In the present work, additively manufactured (AM) 316 L samples were subjected to shot peening with different parameters including the severe shot peening (SSP) procedure. The identical shot peening protocol was also applied to reference samples to evaluate the comparable response. Both the shot peened reference and AM samples were studied for residual stresses, surface topography, microhardness, and the corresponding microstructure. The results indicated, that SSP induced higher values of compressive residual stresses deeper into the samples. This was accompanied by reduced surface roughness, increased grain refinement depth, and higher microhardness near the surface. The SSP resulted in transformation of original austenite to martensite near the surface in the reference samples.