Fatigue life enhancement of TIG-welded 304L stainless steels by shot peening

Shot peening is a cold working process that leads to changes of residual stress in the surface layer and the microstructure. In this paper, we studied the effect of the stress ratio and shot peening on the fatigue life of AISI 304L austenitic stainless steel welded using a fully manual gas tungsten arc welding process (GTAW). The specimens are prepared by welding flat plates with thickness of 1mm using GTAW process and the 308 stainless steel as the filler metal. Results indicate that the fatigue life of the as-welded material under tension-compression loading (stress ratio R=-1) is longer compared to fatigue life under tension-tension loading (stress ratio R=0). Furthermore, the microhardness and fatigue life are found to be improved after shot peening post-welding treatment for durations ranging from 5 to 7min. The improvement in tensile stress and microhardness of treated material is as good as the results reported using the more advanced and costly techniques. Also, the findings suggest that influence of duration of shot peening is more significant on the fatigue life than on the microhardness.