Effect of TaC Contents on Thermal Shock Resistance of Ti (C,N) Based Cermets

Ti(C,N)-based cermets with TaC contents of 0%, 2wt%, 4wt% and 6wt% were prepared by powder metallurgy process, and the effects of TaC contents on thermal shock resistance of the cermets were studied by an indentation-quench method. The results show that the length of cracks increased with the increase of the number of thermal shock, and the cracks mainly propagated along the interfaces between ceramic phase and metallic phase, and also propagated in metallic phase. The cermet with TaC content of 2wt% exhibited the best thermal shock resistance due to the fine grains, the homogeneous microstructure and the moderate thickness of rim phase, which gave rise to a slowest crack propagation and minimum loss of both bending strength and hardness after thermal shock at 500 ℃ for many times. The loss of hardness of Ti(C,N)-based cermets was very small, but the residual bending strength decreased dramatically.