Design a self-reinforcement buffer layer to assist braze SiC and Nb with Cu-xTiH₂ filler alloy

A buffer layer was designed to assist to braze SiC and Nb. The effect of brazing temperature and holding time on the microstructure and the shear strength of the joint was analyzed. The strengthening mechanism of the joint was evaluated. The results found that the SiC-Nb joint was brazed with Cu-5TiH₂, because of its good wettability on the surface of SiC. The typical microstructure of SiC-Nb joint brazed at 1060 °C for 5 min was SiC/C particles + TiC + Cu(s,s)/α-Ti + Nb(s,s)/Cu(s,s)+(Ti,Nb)₅Si₃+Ti₅Si₃/α-Ti/(Ti,Nb)Si/Nb. In addition, a buffer layer formed, which was consisted of two parts: reaction layer (α-Ti + Nb(s,s)) and infiltration layer (much C particles, little TiC and Cu(s,s)). With brazing temperature and holding time increasing, element Nb continuously diffused into brazing seam and solidified into α-Ti. With Nb content increasing, the α-Ti existed in the form of discontinuous to continuous layer, and then to particles. When Nb solidified into α-Ti continuous layer, the strength of the layer was improved and effective joining between SiC and Nb formed. In addition, the buffer layer was contributed to forming a good gradient transition of coefficient of thermal expansion (CTE), and released residual stress. So, the shear strength of the joint was increased to 52.6 MPa.