Study on the rapid synthesis of high-entropy carbonitride powder and its remarkable hardening effects on cemented carbide tool materials

As a novel high-entropy ceramic material with a multi-cation and multi-anion sublattice structure, high-entropy carbonitride ceramics (HECNs) have exhibited outstanding comprehensive properties and attracted increasing attention. In this study, a new WC-based cemented carbide material reinforced by high-entropy carbonitride (Ti0.2W0.2Mo0.2V0.2Nb0.2)(C0.7N0.3) (marked as HECN) was successfully fabricated by vacuum hot-pressed sintering. The mutual constraints between hardness and fracture toughness in extant WC-Co cemented carbide tool materials and their deficient high-temperature mechanical properties were effectively addressed. Moreover, for the low efficiency of the traditional carbothermal reduction nitridation, a novel method for rapidly preparing HECN powder was firstly proposed, namely the microwave-assisted carbothermal reduction nitridation, which could accelerate the heating rate and shorten the holding time. Single-phase HECN powder was successfully synthesized by this method, and the impacts of varying HECN content on the room and high-temperature mechanical properties of WC-based cemented carbide were investigated combined with the microstructure analysis by XRD\SEM. The results revealed that HECN effectively inhibited the grain growth of WC in cemented carbide, and the refined WC grains provided a high-volume fraction of grain boundaries, which prevented dislocation movement and increased the hardness. With the optimized HECN content of 10 wt%, the Vickers hardness and fracture toughness of WC-HECN-Co composite reached 21.58 ± 0.36 GPa and 12.27 ± 1.17 MPa∙m1/2 respectively. Furthermore, WC-10HECN-10Co composites possessed outstanding high-temperature hardness and maintained a high hardness value of 13.16 ± 0.30 GPa at 800 °C, 37% higher than that of WC-10Co. The findings of this research hold significant practical implications for applying cemented carbide cutting tools in high-speed dry cutting.