Microstructure and strength of the C_f/SiC composite joint brazed with Co-Nb-Pd-Ni-V filler alloy

The C_f/SiC composite joint was brazed with newly-designed Co-Nb-Pd-Ni-V filler alloy at the brazing temperature from 1 200℃ to 1 320℃, and the brazing time was fixed at 10 min. The results showed that elements V and Nb in filler alloy played active roles in the interfacial reactions during the brazing procedure, and two interfacial reaction layers VC and NbC were formed at the C_f/SiC surface. Under the brazing condition of 1 280℃/-10 min, the joint microstructure can be characterized as (VC/NbC) double layers/(Co, Ni)₂Si + CoSi + NbC + Pd₂Si/(NbC/VC) double layers. The optimum joint strength can be achieved brazed at 1 280℃ for 10 min, and the room-temperature bend strength was 61.0 MPa. Furthermore, the joint strength tested at 900 and 1 000℃ was even elevated to 83.2 and 87.7 MPa, respectively. The good high-temperature joint strength can be attributed to the formation of high-melting-point compounds, such as NbC and Pd₂Si.