Effect of medium and high entropy carbides on the microstructure and mechanical performance of Ti(C,N) based cermets

Abstract

Medium/high entropy carbides are introduced into Ti(C,N)-based cermet as reinforcing phases because of excellent comprehensive properties. In this work, (TiNbMoW)C₄ (Medium-entropy carbides) and (TiNbTaMoW)C₅ (High-entropy carbides) were prepared by carbothermal reduction method, and Ti(C,N)-based cermets were vacuum sintered with gradient change of carbides. The effects of medium/high entropy carbides on the phase composition, microstructure, mechanical performance, friction and wear performance of Ti(C,N)-based cermets were studied. The results showed that medium/high entropy carbides transformed carbonitride solid solution, and proper amount of medium/high entropy carbides was beneficial to the formation of complete core-rim structure. The core-rim structure distribution of black core/white inner rim/Gy outer rim increased at first and then decreased with the increasing of carbides. The outstanding mechanical performance of Ti(C,N)-based cermets with high/medium entropy carbides were achieved because of synergistic effects of three parts: a)Inner stress decreasing induced by low lattice mismatch of black core/white inner rim/Gy outer rim, b)Grains refinement of overall core-rim structure, c) lattice distortion of high entropy effect. In addition, compared to pressure sintering method, the highest flexural strength was superior in pressureless sintering. Furthermore, high/medium entropy carbides also play a role in stabilizing friction coefficient and reducing wear rate.