Fatigue inhomogeneity of thick 316L stainless steel joints fabricated by ultra-high power laser-MIG hybrid welding

The ultra-high power laser-MIG hybrid welding technique provides an effective method for thick-walled components joining, but the fatigue properties of joints are rarely reported. This research aims to unveil the fatigue behavior evolution of thick weldments along penetration direction. The fitted S-N curves are derived and results show that the fatigue strength presents a downtrend and failure location is transferred from heat affected zone to weld center in depth direction. The mechanism of fatigue crack initiation and propagation are discussed, and find that the shrinkage cavity in lower layer will reduce fatigue performance. The research results provide theoretical guidance for the service of ultra-high power laser-MIG hybrid welded joints