Preparation of Rare Earth Modified Cobalt Powders by Ball Milling and Its Effects on Microstructure and Properties of WC-Co Cemented Carbide

Milled mixture with uniformly distributed ceria powders were synthesized by incorporating CeO₂ into cobalt (Co) powders using the first-step planetary ball milling method. Subsequently, WC-Co cemented carbides were prepared by the second-step planetary milling and spark plasma sintering processes using WC powders and CeO₂-Co powders as raw materials. The results indicated that the first-step ball milling process enhanced the dispersion of CeO₂ within the Co powders. After the first-step ball milling process, the incorporation of Co and CeO₂ promoted the formation of a homogeneously distributed phase within the matrix, thereby facilitating the precipitation of intermediate phases. Increasing the first-step ball milling time improved the density, Vickers hardness, fracture toughness, wear resistance, and corrosion resistance of cemented carbide. The overall properties of cemented carbide stabilized as the first-step ball milling period approached 48 hours. The alloy achieved a density of 99.3%, a hardness of 1919.32 Hv₃₀, a fracture toughness of 11.23 MPa•m^1/2, and a coefficient of friction (COF) of 0.52. The two-step ball milling method used in this thesis strengthened the Co-binder phase, inhibited WC grain growth, and enhanced the overall performance of cemented carbides. These findings demonstrate a novel approach for optimizing the microstructure and mechanical properties of WC-Co cemented carbides.