Microstructure characteristics in TIG welded joint of Mo–Cu composite and 18-8 stainless steel

The welding of Mo–Cu composite and 18-8 stainless steel was carried out by Tungsten Inert Gas welding process with Cr–Ni fillet wires. The microstructure, element distribution, phase constituents and microhardness of the joint were analysed. The results indicate that austenite and ferrite phases were obtained in the weld metal. Austenite and delta ferrite structures were observed in the fusion zone near 18-8 stainless steel. Cu agglomeration regions formed in Mo–Cu composite heat affected zone during welding. The microhardness near the fusion zone at Mo–Cu composite side increased from weld metal to fusion zone, and the peak value appeared near the boundary between fusion zone and Mo–Cu composite due to the generation of high hardness and brittleness Fe–Mo intermetallic compounds. The phase constituents near the fusion zone at Mo–Cu composite are Mo, Cu and γ-Fe (Ni), Cu3.8Ni and the Fe–Mo compound Fe0.54Mo0.73.