Microstructure and properties of Ti(C, N)-based cermet with multi-core-rim microstructure: effect of (Ti, W, Ta) (C, N) pre-solid solution composition

Gasping the controlling mechanism of multi-core-rim structure, like the ratio of multi-cores and the rim thickness, is a key to develop Ti(C, N)-based cermets with high performances. In this work, three types of cermets with the same nominal composition were fabricated by doping self-made (Ti, W, Ta) (C, N) pre-solid solution powders with different compositions, (Ti, 61.3 W, 8.6Ta) (C, N), (Ti, 53.3 W, 7.5Ta) (C, N) and (Ti, 47.1 W, 6.6Ta) (C, N). Effect of the composition of (Ti, W, Ta) (C, N) pre-solid solutions on the multi-core-rim microstructure and mechanical properties of cermets was investigated. Results showed that the decrease of W and Ta contents in the pre-solid solutions leads to an increase of white cores with thinner rims and a decrease of black cores with thicker rims. Thermodynamic calculations indicated that the decrease of W and Ta contents strengthens the thermal stability of the pre-solid solutions. With the decrease of the thermal stability difference between black core Ti(C, N) and white core (Ti, W, Ta) (C, N), more rimless black particles are reserved via Ostwald ripening process. The rim thickness and core size were statistically analyzed, which indicates that the cermet doping medium-solid-solution (Ti, 53.3 W, 7.5Ta) (C, N) exhibits smallest ceramic grains with thinnest rims. An optimal comprehensive mechanical performance was obtained in the cermet doping (Ti, 53.3 W, 7.5Ta) (C, N). It implies that an appropriate pre-solid solution of W and Ta in (Ti, W, Ta) (C, N) promises fine multi-core-rim structure and thus sound mechanical properties of Ti(C, N)-based cermets can be obtained under the same condition of alloy composition and processing parameters.