Microstructural Evaluation of Ti(C_0.7N_0.3)-Mo₂C-xNbC-Ni Cermets

Abstract

The microstructures of Ti(C_0.7N_0.3)-19Mo₂C-xNbC-24Ni cermets (x = 0, 5, 10, 15, and 20) were studied. The cermets consisted of Ti(C,N) and solid-soluted Ti(C,N) as the hard phase with metallic Ni as a binder phase. The solid-soluted Ti(C,N) was found to surround Ti(C,N) phases, forming core-rim structures in the cermets with low NbC content. Phase separation between the Ti(C,N) and solid-soluted Ti(C,N) occurred in the cermets with higher NbC content. TEM analysis showed solid-soluted Ti(C,N) to nucleate surrouunding Ti(C,N) for 5NbC, but in 20NbC it nucleated within the Ni binder phase. The Nb content in the solid-soluted Ti(C,N) of the composite with 20NbC was higher than that of 5NbC. A hard phase separation occurred when the lattice constant of solid-soluted Ti(C,N) exceeded 4.328 Å.