Low temperature synthesis and densification of (Ti,V,Nb,Ta,Mo)(C,N) high-entropy carbonitride ceramics

Abstract

The single-phase (Ti0.2V0.2Nb0.2Ta0.2Mo0.2)(C0.9N0.1) high-entropy carbonitride powder with an average particle size of 203 nm and a low oxygen content of 0.2915 wt% was synthesized by the carbothermal reduction-nitridation method at 1600 °C for 4 h. Subsequently, (Ti,V,Nb,Ta,Mo)(C,N) high-entropy carbonitride ceramics were prepared by hot pressing at temperatures of 1600 °C to 1900 °C. Increasing the sintering temperature is conducive to the uniform distribution of metallic elements, however, the hardness of high-entropy carbonitride ceramics is also reduced. (Ti,V,Nb,Ta,Mo)(C,N) ceramic hot-pressed at 1600 °C for 1 h has a relative density of 99.8%, an average grain size of 0.37 ± 0.08 µm, nanoindentation hardness of 32.4 ± 0.9 GPa, Vickers’ hardness of 24.0 ± 0.7 GPa at 9.8 N and fracture toughness of 4.87 ± 0.25 MPa·m1/2, which is comparable to those of high-entropy carbides and nitrides. In this study, a novel and convenient method for the preparation of (Ti,V,Nb,Ta,Mo)(C,N) high-entropy carbonitride ceramics was established.