Crossed-Wire Laser Microwelding of Pt-10 Pct Ir to 316 LVM Stainless Steel: Part II. Effect of Orientation on Joining Mechanism

With the increasing complexity of medical devices and with efforts to reduce manufacturing costs, challenges arise in joining dissimilar materials. In this study, the laser weldability of dissimilar joints between Pt-10 pct Ir and 316 low-carbon vacuum melted (LVM) stainless steel (SS) crossed wires was investigated by characterizing the weld geometry, joint strength, morphology of weld cross sections, and differences in joining behavior, depending on which material is subject to the incident laser beam. With the Pt-Ir alloy on top, a significant amount of porosity was observed on the surface of the welds as well as throughout the weld cross sections. This unique form of porosity is believed to be a result of preferential vaporization of 316 LVM SS alloying elements that become mixed with the molten Pt-10 pct Ir during welding. The joining mechanism documented in micrographs of cross-sectioned welds was found to transition from laser brazing to fusion welding. It is inferred that the orientation of the two dissimilar metals (i.e., which material is subject to the incident laser beam) plays an important role in weld quality of crossed-wire laser welds.