Fatigue behavior of welded joints of a Ni-Fe-based superalloy

This study investigated the fatigue behavior of butt weld joints in a Ni-Fe-based superalloy GH1140 at 650 degrees C. The welded joints were prepared by the gas tungsten arc welding process on GH1140 plates with a thickness of 20 mm and a 45 degrees K-shape groove. Vickers hardness tests on the cross-section of the welded joints showed slightly lower hardness in the weld center compared to the base metal. Fatigue test results demonstrated a reduction in fatigue lifetime for the welded joints compared to the base metal, attributable to the combined effects of reduced hardness in the weld metal and material heterogeneity. The reduction in lifetime was found to be stress-dependent, with a transition from fatigue fracture at lower stress levels to shear fracture at higher stress levels. Moreover, an empirical fatigue lifetime prediction model was used to predict the fatigue lifetime of the welded joints, showing good agreement with experimental data.