Active brazing of C/C composites and single crystal Ni-based superalloy: Interfacial microstructure and formation mechanism

Abstract Joining between C/C composites and single crystal Ni-based superalloy is of great significance to promote their wide application in aerospace. A sound joint of them is successfully obtained by active brazing with the AgCuTi filler. Interfacial microstructure and joining mechanism of joints are systemically investigated. Effects of brazing parameters on the microstructure and mechanical strength of joints are carefully analyzed. A continuous reaction layer containing the inner fine-grain and outer coarse-grain TiC is formed adjacent to C/C composites. Surprisingly, both Ag and Cu inclusions are observed at the C/C composites interface by careful examination. Especially, Cu inclusions are first detected in this study. In contrast, intense interdiffusion is the main interaction mechanism between the DD3 and the filler. (Ni, Cu)3(Al, Ti) and (Cu, Ni) solid solution (s, s) layers are formed at the DD3 interface. Meanwhile, a large amount of small seed-shape AlNi2Ti phases are formed in the whole joint. The highest shear strength (~36 MPa) is obtained for the joint brazed at 880 °C for 10 min