The Effect of Laser Heat Treatment and Severe Shot Peening on Laser Powder Bed Fusion Manufactured AISI 316L Stainless Steel

Abstract

In this study the effect of laser heat treatment (LHT) and severe shot peening (SSP) on laser powder bed fusion manufactured AISI 316L stainless steel is investigated. The effect of LHT and SSP on the hardness of the surface of the PBF-LB 316L is studied performing microhardness measurements. Microstructure is evaluated in the EBSD investigation. The residual stresses will be measured to determine the influence of LHT and SSP. The effects of LHT and SSP on tensile and bending fatigue strength will be evaluated. LHT altered the microstructure 200 µm from the surface. The grain structure on the surface was more ordered and no substructure or local strains were present. Finer grain features adjacent to the sample surface were found, which are most likely caused by effective recrystallization and fast cooling. The grain morphology was left relatively unchanged when SSP was applied on LHT surface. However, local deformation has occurred on the surface, and clear orientation gradient within grains is seen. LHT had no effect on the hardness. SSP increased the surface hardness by 205%. LHT decreased the yield or tensile strength of the PBF-LB 316L. Residual stress measurements showed that SSP induced a high compressive stress in the PBF-LB 316L. LHT and SSP significantly improved the fatigue strength of the PBF-LB manufactured 316L.