Fatigue characteristics improvement of the TIG-welded 316L specimens with T-joint geometry using laser shock peening

• Improvement in fatigue performance of TIG welded structures was achieved. • LSP results in more predictable fatigue behavior. • LSP is a potential repair technique for pre-damaged welded joints. • The fatigue life can be recovered if the pre-damage is of a reasonable size. In industry, tungsten inert gas (TIG) welding is a widely adopted process for material joining, especially austenitic steels. However, welded joints are more susceptible to fatigue cracks and have shorter and more scattered fatigue lives compared to the base material. The present study investigates the influence of laser shock peening (LSP) on the fatigue performance of TIG-welded 316L stainless steel with T-joint geometry. Three groups of specimens were prepared: as-welded, as-welded and LSP-treated, and pre-damaged welded specimens treated with LSP. The axial fatigue tests were performed and analyzed using the Wöhler curve and Weibull distribution, and the fracture surfaces were examined. The compressive residual stresses (CRS) induced by LSP were determined using both the hole-drilling method and X-ray diffraction. The results demonstrated that LSP can significantly enhance the fatigue performance of the welded specimens, leading to a 25% improvement in fatigue strength, providing the highest fatigue data reliability, and extending the crack initiation phase by a factor of 7.8. It was shown that LSP can be considered as a promising repair approach for pre-damaged welds. Both as-welded and LSP-treated and pre-damaged LSP-treated groups of specimens exhibited a substantial extension of fatigue life, reaching improvement factors of 3.15 and 2.28, respectively.