Enhancement on the low-pressure shot peened process of monotonic plastic deformation behaviors of Ni–4Cu–3Mo alloy/super austenite stainless steel dissimilar joints using laser beam welding

Abstract

This research paper mainly discusses the low-pressure shot-peened (LPSP) process of 2 mm thick sheet plates of monotonic mechanical behaviors of Ni–4Cu–3Mo alloy/super austenite stainless steel (SASS) dissimilar materials joint by laser beam welding. Three types of butt joint (Sample-1, Sample-2, and Sample-3) configuration methods of the laser beam welding process were implemented at the Ni–4Cu–3Mo alloy/SASS dissimilar weldments and LPSP weldments. The microstructure image of the fusion zone revealed that the high heat inputs were distributed at the grain boundary and the prior coarse grain structures were converted into NiCr and C–Cr with significant improvement in the α'-martensite structure. To achieve continuous improvement in yield strength of LPSP weldments compared to the dissimilar weldments, the plastic deformations rate was decreased in the shot-peened weldments. The base metals of tensile samples length were prepared as ±5 mm; however, samples clearly indicated that the dissimilar weldments and LPSP weldments showed the failure in the fusion zone. The average elongation of dissimilar LPSP weldments was increased by 13%; however, the heat inputs collapsed the grain boundaries growth and the structure was converted into twin boundaries and α-martensite structures. The hardness measurement at the fusion zone of dissimilar and LPSP weldments was performed and the average hardness value of 290 HV at the fusion zone and 211 HV at the heat-affected zone was observed for LPSP weldments. The fracture morphology revealed that neither major cracks nor minor voids at the fusion zone of the tensile sample were formed.