Interface microstructure and mechanism of SiC ceramic vacuum brazed joint

Vacuum brazing of SiC ceramic was conducted using Ti-Zr-Ni-Cu solder. The interface microstructure and its formation mechanism was investigated. Scanning electron microscope (SEM) was used to observe the joint microstructure and conduct local energy spectrum analysis. The results show that the products in the joint interface were mainly TiC, Ti₅Si₃, Zr₂Si, Zr(s, s), Ti(s, s)+Ti₂(Cu, Ni) and (Ti, Zr)(Ni, Cu) phases. The microstructure of the joint interface could be expressed as SiC/TiC/Ti₅Si₃+Zr2Si/Zr(s, s)/Ti(s, s)+Ti₂(Cu, Ni)/(Ti, Zr)(Ni, Cu). The brazing process could be divided into five stages: physical contact between the solder and substrate, melting of solder and formation of reaction layer on the ceramic side, continuous diffusion of melted solder into the substrate, thickness increasing of reaction layer, composition homogenization, ending of reaction on ceramic side and formation of hypereutectic structure, solidification of intermetallic compounds in the center of joint. The shear strength of the joint brazed at 960°C for 10min reached 110 MPa.