Fabricating Ultrathin Plate-Like WC Grains in WC–8Co Hardmetals by Increasing Discharge Intensity During Plasma-Assisted Ball Milling

Abstract: The effects of plasma discharge intensity on the microstructure evolution of ball-milled tungsten (W)–carbon (C)–cobalt (Co) mixtures and the formation mechanism of ultrathin plate-like tungsten carbide (WC) grains prepared by ball milling with and without plasma discharge were investigated. It was found that increasing the plasma discharge intensity during ball milling obviously promoted the formation of a thin flake-like W phase because of the electroplasticity effect and simultaneously lowered the carburization temperature between W and C. A combination of high hardness and transverse rupture strength of 92.9 HRA and 3659 MPa, respectively, was obtained for the WC–8Co alloy fabricated by plasma milling at a gas pressure of 5 × 10 Pa with a dielectric barrier discharge layer thickness of 3 mm. These properties were mainly attributed to the markedly lowered activation energy of the WC phase and generation of highly oriented ultrathin plate-like WC grains by plasma milling. The combination of the flake-like structure of the plasma-milled W aggregate and high specific interfacial area and short diffusion distance of W/C were readily inherited by the ultrathin plate-like WC grains in the sintered WC–Co hardmetals. Graphic Abstract: [Figure not available: see fulltext.]