Microstructure and mechanical properties of WC-CoCrFeNiMoX-based cemented carbide with bimodal WC grain size distribution

Abstract

This study systematically investigates the influence of molybdenum (Mo) content on the microstructure and mechanical properties of WC-CoCrFeNiMo_X high-entropy alloy (HEA)-bonded cemented carbides. Samples were prepared by wet-milling WC powders of varying particle sizes with CoCrFeNiMo_X (X = 0.1, 0.5, 1.0) binders, followed by sintering at 1460°C under multi-atmosphere conditions. The effects of Mo content on phase composition, grain morphology, hardness, and fracture behavior were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mechanical property tests. Results indicate that Mo addition significantly refines WC grains and promotes their spheroidization, achieving a Vickers hardness of 1663.7 HV₃₀, an attribute that reflects superior performance compared to traditional Co-bonded WC materials. However, increasing Mo content exacerbates binder phase embrittlement and carbon deficiency, resulting in a reduction in transverse rupture strength (TRS) as Mo content increases. Fractographic analysis reveals that low-Mo samples exhibit a mixed intergranular-cleavage fracture mode, whereas high-Mo samples predominantly undergo intergranular fracture. Within the studied system, Coarse WC grains enhance toughness by impeding crack propagation. This work highlights the potential of HEA binders for balancing hardness and toughness in cemented carbides, and proposes that optimizing Mo content and suppressing carbon loss are critical strategies for improving comprehensive performance. These findings provide a theoretical foundation for the development of high-performance wear-resistant materials.