Influence of thermal shock and environment temperature on mechanical properties of C/SiC/GH783 joint brazed with Cu-Ti plus Mo

The carbon reinforced silicon carbide ceramic matrix composites (C/SiC) were brazed to Fe-Ni-Co superalloy (GH783) with Cu-Ti + Mo solder under vacuum at 1000 degrees C. The influence of thermal shock (in air at 800 degrees C) and environment temperature on mechanical properties of the joint were investigated. The joint between C/SiC composites and GH783 was dense, crack free, and was comprised of reaction layer, stress relief layer, plastoelastic layer, and diffusion layer. Thermal shock damage and oxidative damage were both existing after the thermal shock. Therefore, the flexural strength of the joint decreased dramatically with the increase of thermal shock times. After 5, 10, and 15 times of thermal shock, the flexural strength of the joint decreased to 42.9, 22.7, and 9.7% of the initial strength, respectively. The flexural strength of the joint decreased dramatically with the increase of environment temperature because of the thermal mismatch between C/SiC and the interface reaction layer. The flexural strength of the joint at 600, 800, and 900 degrees C was decreased to 60, 39, and 29% of that at room temperature, respectively. The C/SiC was brazed to GH783 with Cu-Ti + Mo solder under vacuum at 1000 degrees C. The joint between C/SiC and GH783 was dense and crack free. The flexural strength of the joint decreased dramatically with the increase of thermal shock times. The reaction layer had been completely oxidized which was analyzed by EDS and SEM. The flexural strength of the joint decreased dramatically with the increase of environment temperature. The fracture surface morphology was examined by SEM.