Investigation of Single-Pulse Laser Welding of Dissimilar Metal Combination of Thin SUS303 SS and Cu

The present study investigated the dissimilar metal combination of SUS303 stainless steel (SS) and pure copper C19210 by utilizing a fiber pulse laser to perform lap welding. The weld quality was evaluated through metallurgical and mechanical examinations, including scanning electron microscopy (SEM), optical microscopy (OM), energy dispersive spectroscopy (EDS), as well as tensile and shear tests. The cross-section of the weld joints was observed to examine the penetration inside the molten zone of the pulse laser welding. The incomplete weld penetration depth was confirmed by analyzing the molten pool geometry, which indicated that the penetration depth was proportional to the pulse heat energy input. EDS analysis demonstrated that interdiffusion and dissolution of Cu and SS occurred inside the weld pool, although only a limited amount of Cu was melted. Microhardness (MH) exploration revealed the hardness of the molten zone was lower than that of the heat-affected zone (HAZ) on the SS side, while the hardness on the Cu side, closer to the molten zone, was higher. The results of the tensile test indicated that the fracture occurred in the HAZ on the Cu side, displaying a dimpled fracture mode characteristic of ductile fracture.