Nano TiC modified Ti(C,N)-based cermets with weakened rim-binder interfaces

In order to solve the problems of high internal stress of core-rim structure, and denitrification behavior of Ti(C, N)-based cermets, nano TiC powders were adopted to promote the diffusion-controlled formation of inner rims and to modify the metal-ceramic interfaces. Based on this, Ti(C,N)-based cermets with 0–8 wt% nano TiC were prepared via solid-state nitrogen-pressure sintering and subsequently Ar-pressure HIP sintering. Nano TiC refined the microstructure and resulted in more white core-rim phase with thicker rims, and ultrafine rimless Ti(C,N). Nano TiC greatly affected the rim-binder interfaces via shifting the equilibrium crystal morphology of (Ti,M) (C,N) in Ni–Co from cubic to octahedron. With the increasing nano TiC content, the orientation relationship of rim-binder interface changed from (200)rim//(111)binder to (111)rim//(111)binder, and the interface strain increaseds. Cermets with {200} rim-binder interface exhibited high bending strength but low fracture toughness and tensile strength, owing to the high bonding strength between rim and binder. Otherwise, weakening strength of the rim-binder interface could enhance the toughness via the breaking of ceramic-binder boundaries. A promising route for preparing Ti(C,N)-based cermets with satisfactory mechanical properties was put forward, via adjusting the rim-binder interfaces.