Enhancing the static and dynamic mechanical properties of laser powder bed fusion process built 15–5 precipitation hardening stainless steel specimens by laser shock peening

Abstract

The Additive Manufacturing (AM) of high strength Stainless Steel (SS) metallic parts by Laser Powder Bed Fusion (L-PBF) process has been able to reduce cost and time significantly, leading to a successful adaption in various high technology industries. In this study, the static and dynamic mechanical properties of L-PBF 15–5 Precipitation Hardening (PH) SS in two different loading directions have been studied, and Laser Shock Peening (LSP) has been used as a post-processing tool to improve the part properties. Optimized parameters were chosen for the mechanical property evaluation based on the residual stress profile of the specimens subjected to LSP. Improvement in microhardness, uniaxial tensile properties and high cycle fatigue life due to LSP are reported. With LSP applied on vertically loaded L-PBF 15–5 PH SS specimens (loading axis parallel to building direction), the fatigue life has increased by more than four times, making it comparable to horizontally loaded L-PBF 15–5 PH SS base specimens. Thus, the viability of the LSP process as a post-processing technique to mitigate the fatigue life anisotropy due to loading direction has been established. The associated microstructure and phase analysis revealed an increased depth of plastic deformation with successive LSP shots without causing any phase changes. The central strengthening mechanisms for the enhancement of mechanical properties of L-PBF 15–5 PH SS due to LSP are reported.