Optimizing the brazing process of SiC and Nb using TiNiNb alloy: Evolution of microstructure and mechanical properties

With the increasing demands for more efficient and safer nuclear reactor designs, the development of reliable joints between advanced materials like SiC and Nb has become critical for high-temperature applications. This study investigates the brazing of SiC and Nb using TiNiNb brazing alloy under various process conditions. Through experimental analysis and numerical simulations, the relationship between interfacial reactions, microstructure, and joint performance is revealed. Results show that the brazed joint has a layered structure with primary phases including (Ti, Nb)C, TiNi, and Nb(s, s). Optimal brazing parameters are determined to be 1200 °C and 10 min, yielding a maximum shear strength of 114 MPa at room temperature and 52 MPa at 800 °C. Residual stresses concentrate near the SiC interface, leading to crack initiation and making it the weakest region. Fracture modes transition from brittle at room temperature to mixed brittle-plastic at high temperatures, influenced by phase softening and reduced interfacial strength. These findings provide a theoretical basis for improving brazed joints for high-temperature and nuclear applications.