Residual Stresses, Microstructure, and Mechanical Properties of Laser Beam Butt-Welded Dissimilar Joints of SS321 to Hastelloy C276

This study investigates the feasibility and performance of CO2 laser beam welding for comparing dissimilar metals SS321 and Hastelloy C276, as well as similar joints (SS321-SS321 and C276-C276). Optical and scanning electron microscopy revealed fine dendritic microstructures in the fusion zone (FZ), with epitaxial grain growth near the weld interface and narrow heat-affected zones (HAZ), typical of laser welding. Microhardness profiles showed slightly elevated hardness in the FZ compared to parent materials, with dissimilar joints exhibiting a smooth, continuous profile. The microhardness at the weld is 267 HV, 249 HV, and 258 HV, for SS321, C276, and SS321 to C276, respectively. Tensile tests demonstrated superior mechanical performance of the weld zone, with fractures occurring in the parent metal on the SS321 side of the dissimilar joint. Residual stress measurements using x-ray diffraction showed peak tensile stress values well within the base metals’ yield strength, and the safety factor was 2.16 for SS321, 1.89 for C276, and 1.48 for the dissimilar joint. These results confirm that CO2 laser welding is a viable and effective method for producing high-quality, mechanically robust dissimilar joints between SS321 and Hastelloy C276.