Preparation and mechanical properties of (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4)-Co high-entropy cermets

A novel (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4)-Co high-entropy cermets were prepared by two-steps method and the microstructure and mechanical properties were investigated. The single-phase high-entropy carbonitride (HECN) (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4) powders were synthesized at 1600 °C. Subsequently, the HECN-Co cermets were successfully fabricated by the pressureless sintering technique. The results revealed that HECN powders (grain size ~0.79 μm) with uniform composition could be prepared at a lower temperature (1600 °C) by using oxide and carbon powders as raw materials. This preparation method also maintained the oxygen content and free carbon at low levels of 0.13 wt% and 0.03 wt%, respectively. The HECN-Co high-entropy cermets sintered at 1500 °C showed uniform distribution of the metal phase along the ceramic phase and good denseness (apparent porosity of only 0.08%). In addition, the samples possessed excellent mechanical properties, with hardness and fracture toughness of 15.72 GPa and 12.9 MPa·m1/2. Because of the unique features of high-entropy ceramics and the effective combination of ceramic and metal phases, HECN-based high-entropy cermets offer excellent overall properties. •A novel (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4)-Co high-entropy cermets were designed and prepared.•(Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4) powders were synthesized at 1600 °C with the O 0.13 wt% and Cf 0.03 wt%.•(Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4)-Co cermets were fabricated at 1500 °C with HV 15.72 GPa and KIC 12.9 MPa·m1/2.•The synthesis of (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)(C0.6N0.4) powders and its densification behavior were discussed.