Microstructure of Ti(CN)–WC–NbC–Ni Cermets

An investigation of the microstructural evolution and dissolution phenomena in a Ti(C_0.7N_0.3)– x WC– y NbC–20Ni system is reported. In Ti(C_0.7N_0.3)– y NbC–20Ni systems, a phase separation occurs between the Ti(CN) core and the (Ti,Nb)(CN) rim phases when the system contains >15 wt% NbC. This phase separation results from the increased misfit between the cores and the solid-solution rim phases with the addition of NbC. Based on data obtained from a previous study and compositional analyses of the rim structure of the Ti(C_0.7N_0.3)– y NbC–20Ni system, the average dissolution rates of WC and NbC appear to be approximately the same with respect to that of Ti(CN), under given sintering conditions (1510°C for 1 h). In addition, compositional changes in the rim structure of the Ti(C_0.7N_0.3)– x WC– y NbC–20Ni system are compared with those for a Ti(C_0.7N_0.3)– x WC–20Ni system to explain the effect of NbC on WC dissolution in the Ti(C_0.7N_0.3)–WC–NbC–Ni system. The presence of NbC in the Ti(C_0.7N_0.3) –x WC–20Ni system is found to suppress the dissolution of WC.