Stress corrosion cracking performance of LPBF-built 316L stainless steel post-processed with heat treatment and severe shot peening

Abstract

This study investigated stress corrosion cracking (SCC) susceptibility in laser powder bed fusion (LPBF) printed 316L stainless steel under corrosive conditions. LPBF process inherently introduces residual stresses and surface defects that can compromise material integrity in aggressive environments. Post-processing techniques, specifically severe shot peening (SSP), heat treatments at 600°C and 900°C, and their combinations were employed to mitigate these issues. SCC testing in a boiling 25% NaCl solution assessed cracking over a period of five weeks. The results demonstrate that while SSP initially introduced compressive residual stresses potentially enhancing SCC resistance, subsequent mechanical deformation by U-bending diminished these benefits, leading to increased susceptibility to cracking. Tensile stresses induced by U-bending appeared to override the benefits of defect closure and reduced surface roughness, resulting in cracking. Notably, only specimens subjected to AB + SSP and HT600 + SSP conditions exhibited cracking during the testing period, highlighting the complex interplay between residual stresses, mechanical deformation, and SCC behaviour.