Research on the regulation mechanism of laser shock peening on SCC performance of thin-walled austenitic welded joints

To address the susceptibility of thin-walled austenitic stainless steel welded joints in nuclear power plants to stress corrosion cracking (SCC) under multi-field coupling environments, this study employs laser shock peening (LSP) technology for surface treatment to enhance their SCC resistance. By controlling LSP parameters, the research achieved redistribution of residual stresses and the construction of gradient nanostructures, effectively suppressing the initiation and propagation of SCC. Experimental results indicate that LSP treatment transforms residual tensile stresses on the welded joint surface into compressive stresses, significantly reducing the driving force for crack propagation. Simultaneously, the formed gradient nanostructure further mitigates stress concentration, thereby enhancing the material’s crack resistance. EDS analysis reveals that LSP treatment induces redistribution of Cr and Ni elements at grain boundaries, increasing precipitation of M 23 C 6 -type carbides. Although local chromium-depleted zones may elevate the risk of microcrack initiation, the strengthening effect of the gradient nanostructure predominantly governs the overall improvement in SCC resistance. Furthermore, optimized LSP parameters for thin-walled structures were established, and a three-stage strengthening model was developed, providing theoretical guidance for selecting optimal process parameters in practical applications. This research offers new technological pathways and theoretical support for enhancing SCC protection in critical thin-walled welded components of nuclear power plants.