High entropy alloy bonded cemented carbides: Composition, processing, microstructure, properties and applications

WC-Co cemented carbide has been widely used in the past 100 years due to its excellent properties. However, the incorporation of Co does bring about some adverse effects such as reduced hardness/wear resistance, decreased oxidation/corrosion resistance, deteriorated high-temperature performance, depressed thermal fatigue resistance resulting from thermal stresses, toxicity, and high cost. High-entropy alloy (HEA) possesses superior microstructure stability, splendid high-temperature softening resistance and thermal-mechanical-chemical properties to traditional Co binder, making HEA the most potential alternative binder to Co in hardmetals. Herein, this review aims to establish the processing-composition-microstructure-property relationships, so as to significantly enhance the service reliability of HEA bonded cemented carbides. We initially introduce the development of cemented carbides with alternative binders, subsequently, comprehensively elucidate the synthesis of HEA powder together with the four effects of HEA, then summary densification factors including mixed carbon content, microstructure evolution and advanced sintering techniques. In addition, the incorporation of additive on further improving the properties of HEA bonded cemented carbides is discussed. Furthermore, the hardness versus toughness relationship and tribological properties are analyzed to explore the advance of HEA bonded hardmetals in comparison with traditional cemented carbides. This review closes with consideration of potential applications as well as concluding remarks and future directions.