Effects of binders on the microstructures and mechanical properties of ultrafine WC-10%AlxCoCrCuFeNi composites by spark plasma sintering

Abstract

Ultrafine WC cemented carbides with 10 wt% mechanically alloyed AlxCoCrCuFeNi (x is the aluminium content in molar ratio and ranges from 0 to 1.5) high-entropy alloy (HEA) binders were fabricated by spark plasma sintering. The influences of the HEA binders on the microstructures and mechanical properties of WC-HEA cemented carbides were discussed. Due to the sluggish diffusion effect of the HEA binders, the WC grain growth activation energy of WC-HEA cemented carbides is significantly higher than that of WC-Co alloy. Consequently, the grain growth of WC is inhibited during sintering, and an ultrafine microstructure can be obtained. With increasing Al content of HEA binders, both the relative density of WC-HEA cemented carbides and the hardness of HEA binders increase, which contributes to the high hardness of WC-HEA cemented carbides. The fracture toughness of WC-HEA cemented carbides is codetermined by the wettability of HEAs on WC and the intrinsic sintering property and deformability of HEA binders. Therefore, the WC-HEA cemented carbide with 10 wt% Al0.5CoCrCuFeNi high-entropy alloy binder exhibits the best combination of Vickers hardness and fracture toughness, which are 2071 ± 6 HV30 and 10.3 ± 0.1 MPa m1/2, respectively.