Microstructural and mechanical characterizations of W/CuCrZr and W/steel joints brazed with Cu-22TiH2 filler

Microstructural characterizations of both W/CuCrZr and W/SS301 (stainless steel 301) joints reveal the favorable bonding of the filler to the substrates and negligible occurrence of inter-diffusions (or interfacial reactions) at the W/filler layer interface. The filler layer of W/CuCrZr joint is mainly made up of Cu-based solid solution (Cu (ss)) and intermetallic Ti-Cu phases. In the case of the W/SS301 joint, the filler layer comprises Cu (ss) and intermetallics including Ti-Cu and Ti-Fe. A reaction layer of Fe2Ti with a thickness of about 10 μm is formed adjacent to the filler layer through the reaction of Ti with Fe from the SS301 substrate. A diffusion layer containing σ-phase is developed at the interface between the Fe2Ti reaction layer and the SS301 substrate. The mechanical characterizations including microhardness and shear strength of both W/CuCrZr and W/SS301 joints have been performed. The results of microhardness in the interfacial zone are highly related to the joint microstructure.