Understanding the stress corrosion cracking resistance of laser shock surface patterned austenitic stainless-steel weld joints

Stress corrosion cracking (SCC) failures of austenitic stainless steel (ASS)-based dry storage canister (DSC) weld joints are a potential safety hazard in nuclear applications. The present study aims to provide deeper insights into the effect of novel laser shock surface patterning (LSSP) on the SCC resistance of DSC weld joints. The LSSP experiments were performed with varying intensity, covering the fusion zone (FZ), heat-affected zone (HAZ), and base material (BM). The SCC testing was conducted in boiling MgCl2 on U-bend specimens. The laser-induced shock wave developed during LSSP simultaneously caused strengthening and patterning effects by forming an array of micro-indentations. LSSP leads to austenitic to strain-induced martensitic (α′-phase) transformation, residual compressive stress (RCS), and grain refinement. In addition, surface hardness was improved, and surface roughness and volume fraction of α′-phase reduced significantly. The SCC testing on LSSP’ed U-bend specimens revealed enhanced SCC resistance compared to the unpeened U bends, which can be attributed to the presence of RCS in the subsurface and the minimal effect of surface roughness and volume fraction of α′-phase.