Laser spot microwelding of crossed Pt/Ir alloy wire to 316 LVM stainless steel wire

The crossed wires of Pt alloy and 316 low-carbon vacuum melted stainless steel (SS) were spot-welded with YAG laser welder. The effects of single-pulse peak power on the surfaces, interfacial metallurgical phenomena and mechanical properties were investigated. With increase of laser peak power, the joint interfacial bonding mechanisms changed from short-time braze welding to the combination of partial short-time braze welding and partial fusion welding, and then total fusion welding when the SS wire was positioned at the upside of joint. And the joint breaking force remarkably increased, then kept at a relatively stable stage with a value close to the strength of original Pt/Ir wire, and finally decreased to 0 N due to the overmelting. The joints demonstrated different tensile failure modes, i.e., at brazed-interface only, mixture of partially at bonding interface and partially in Pt/Ir, in Pt/Ir only, and finally in welds or in SS wire due to the overmelting. In comparison, solidification pores in weld were more readily formed when the SS wire was positioned at the downside of joint. Finally, an optimal welding technology for strong and smooth joints was obtained. Copyright © 2010 MS&T'10®.