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

Abstract

A novel (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 )-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) (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 ) 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·m 1/2 . 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 (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 )-Co high-entropy cermets were designed and prepared. • (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 ) powders were synthesized at 1600 °C with the O 0.13 wt% and C f 0.03 wt%. • (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 )-Co cermets were fabricated at 1500 °C with H V 15.72 GPa and K IC 12.9 MPa·m 1/2 . • The synthesis of (Ti 0.2 Zr 0.2 V 0.2 Nb 0.2 Ta 0.2 )(C 0.6 N 0.4 ) powders and its densification behavior were discussed.