Low-cycle fatigue of 1Cr-18Ni-9Ti stainless steel and related weld metal under axial, torsional and 90° out-of-phase loading

The fatigue behaviour of base metal and weld joints of 1Cr-18Ni-9Ti stainless steel has been studied under uniaxial, torsional and 90degrees out-of-phase loading. A significant degree of additional hardening is found for both base metal and weld metal under 90degrees out-of-phase loading. Both base metal and weld metal have the same cyclic stable stress-strain relationship under torsional cyclic loading and 90degrees out-of-phase cyclic loading. Base metal exhibits higher cyclic stress than weld metal under uniaxial loading, and Young's modulus and yield stress of weld metal are smaller than those of base metal. Weld metal exhibited lower fatigue resistance than base metal under uniaxial and torsional loading, but no significant difference was found between the two materials under 900 out-of-phase loading. A large scatter of fatigue life is observed for weld metal, perhaps because of heterogeneity of the microstructure. The Wang-Brown (WB) damage parameter and the Fatemi-Socie (FS) damage parameter, both based on the shear critical plane approach, were evaluated relative to the fatigue data obtained.