Abstract
Surface treatment by laser irradiation leads to softening in a surface region for Ni-base superalloys. This paper investigates the utility of surface softening to reduce a stress concentration at the weld toe of Ni-base alloy joints. Three-dimensional FE-analysis is conducted to obtain the stress-strain fields of the welded joints. It is revealed that surface softening is effective to reduce the stress concentration at the weld toe. The relaxation of stress concentration is almost proportional to the degree of softening. The demerit of surface softening is found in an elevation of strain level at the weld toe. However, the strain concentration can be marginal in the applied stress level below 0.5σYB(σYB: yield stress of base metal), at which initial yielding occurs at the weld toe. It is expected from the results that surface softening will improve a high-cycle fatigue property of welded joints.
