Microstructure evolution and its effect on the mechanical properties of the ZrC–SiC composite joint diffusion bonded with pure Ni foil

The ZrC—20 vol% SiC composite was diffusion bonded with pure Ni foil as the interlayer. The interfacial microstructure evolution and its effect on the mechanical property of the joint were investigated. The results showed that Ni reacted preferentially with SiC. The corresponding reaction products were Ni2Si and C. During longer holding time or at higher joining temperature, the reaction product Ni2Si separated from C and penetrated along ZrC boundaries. Meanwhile, C transformed into pieces of graphite. Beside the ZrC/Ni interface, nickel based solid solution and fine graphite were observed due to the slight reaction between ZrC and Ni. With increasing in joining temperature, Ni was consumed gradually and the transition layer increased in thickness. The shear strength of the joints increased to the maximum and then decreased with increasing joining temperature from 800 °C to 1200 °C. The maximal value of 168 MPa was obtained when joined at 1000 °C under 20 MPa for 30 min.