TZM/graphite interface behavior in high-temperature brazing by Ti-based brazing filler materials

Graphite was successfully brazed to TZM alloy using the Ti-56Ni, Ti-8.5Si, Ti-33Cr and Ti-30V-3Mo brazing filler materials, respectively, and the corresponding brazing temperatures ranged from 1300 to 1700 °C. The results show that the microstructure of TZM/graphite braze metal was composed of NiTi and Ni3Ti compounds when using Ti-56Ni brazing filler, and the discontinuous TiC compounds were found at the Ti-56Ni/graphite side. When using the Ti-8.5Si, Ti-33Cr and Ti-30V-Mo brazing fillers, the metallurgical combination was obtained due to the formation of the Ti-Mo solid solution at the TZM/brazing filler side and the TiC reaction layer at the graphite/brazing filler side. The fracture was occurred at the interface of TiC/graphite during shear test, which indicated the poorer bonding strength between the graphite and granular TiC.