Infrared brazing of Mo using the 70Au-22Ni-8Pd alloy

Infrared brazing of Mo using the 70Au-22Ni-8Pd braze alloy is performed in the experiment. Both Au-rich and Ni-rich phases are observed in the infrared brazed joint at 1050 °C. The Au in the molten braze is not reacted with the Mo substrate, but the Ni in the braze preferentially reacts with the Mo. With increasing the brazing temperature and/or time, the interfacial reaction between the molten braze and Mo substrate is greatly enhanced, and the angular MoNi intermetallic compound is formed in the brazed joint, especially for the furnace brazed specimen due to its slow thermal history. The formation of interfacial MoNi intermetallic compound in the brazed joint is detrimental to its bonding strength. Cleavage dominated fracture is widely observed from the fractograph of furnace brazed specimen. Additionally, the application of rapid infrared brazing is a very effective process to inhibit excessive growth of the interfacial MoNi phase in the joint.