Effect of post weld heat treatment on damage mechanism of gas tungsten arc welded 308L stainless steel during creep-fatigue

Strain controlled creep-fatigue tests were conducted on gas-tungsten-arc welded (GTAW) 308L stainless steel joints at elevated temperature. The influence of post-weld heat treatment (PWHT) on the ferrite morphology and creep-fatigue behaviors of the weldment were investigated. The microstructure evolution and crack propagation behavior of the as-welded and post weld heat treated (PWHT) weldments during creep-fatigue test were examined with optical microscope (OM) and scanning electron microscope (SEM). Energy dispersive spectroscopy (EDS) was also used for intermetallic phase identification. It was found that high temperature PWHT reduced the amount of δ-ferrite in the weldment, and the creep-fatigue life increased with the increasing PWHT temperature. After high temperature PWHT, the crack propagation character was transformed from intergranular mode to mixed mode. High temperature PWHT resulted in the broken of the continuous δ-ferrite network and promoted the creep-fatigue resistance of the weldment.