The effect of post weld heat treatment on the creep-fatigue behavior of gas tungsten arc welded 308L stainless steel

Gas tungsten arc (GTA) weld joints were made from 308L stainless steel. The microstructure and phase transformation of the as welded and post weld heat treated (PWHT) weldments before and after creep-fatigue test were examined using transmission electron microscopy (TEM). The results show that the primary cyclic softening is replaced by primary hardening after high temperature PWHT, which is due to the rearrangement of dislocation and the relief of residual stress. The primary δ-ferrite mainly transformed into sigma phase during the creep-fatigue test, and the remaining amount of δ-ferrite depends on the PWHT and creep-fatigue test conditions. Further more, high temperature PWHT shows a tendency to retard the δ-ferrite to σ-phase transformation, which in turn promotes the creep-fatigue resistance of the weldment.