Study On Technology And Mechanism Of （C_fSiC_f）/SiBCN Ceramic Brazing With High Temperature Alloy

(Cf-Si Cf)/Si BCN is one of the advanced ceramic matetials applied in high-temperature environments. The added Cf and Si Cf can enhance the ceramic. It still keep good performance under 1400℃. Due to the difficulty of its various size and shape producing with current sintering process, it makes great significance to connect the ceramic together. In this study, two kinds of high-temperature brazing alloys were used to join the ceramic, and the joining properties and mechanism were studied.First, the technological parameters and joining mechanism with Ti-Ni system were studied. A Ti-Ni solder consisting of five components in Ti-Ni system was chosen to join the ceramic, the joining temperature of which was between 1200 o C~1300o C. The compositon of Ni had important influence on the joint, and the joint could be connected well only when the content of Ni was more than 50 at.% and the foils laminated in Ni/Ti/Ni way. The interface between ceramic and braze layer would crack with too much Ti brittle compounds at interface, when the content of Ti was more than 50 at.% or foils laminated in Ti/Ni/Ti way. The diffusion layer became thicker when increasing the content of Ni or increasing the brazing temperature. The mechanical proporty test showed relatively low strength of Ti-Ni joints, the maximum strength reaching 25 MPa when brazed with Ti-60 Ni at 1250 oC. The stess distribution state were researched by finite element analysis. 5 kinds of models was established. The maximum stress decreased when the diffusion layer thickness and Ni content increased.Ti-Si brazing alloys were made using electric arc melting method. The wettability of Ti-84 Si was good, the connect angle was 17°, Ti-13.5Si couldn’t form connetion with ceramic. Ti-84 Si was used to join the ceramic, and the brazing temperature was between1380℃~1420℃, the holding time between 5min~20min, the cooling rate 15℃/min or40 ℃ /min. The brazing seam was mainly composed of eutectic structure, and also contained regular shape Ti(C0.3,N0.7) and Ti(Bx,Cy). The structure turned to be homogeneous and the Ti compound grew, when increasing temperature or holding time.Ti compound grew up in a multi-nuclei growth mode, and the final structure had strong crystallographic features. The mechanical proporty test result showed relatively high strength of Ti-84 Si joints, the maximum strength reaching 82 MPa when brazed with20 min holding time at 1250℃. The nano-indentation tests showed the phase interface can restrain the crack from extending.