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In this study, the effects of Cr₃C₂, VC, and TaC on microstructure, WC grain morphology and mechanical properties of WC–10 wt. % Co ultrafine cemented carbides were investigated. The experimental results showed that WC grains size decreased and size distribution became narrow by adding Cr₃C₂, VC, and TaC. The inhibition efficiency was in the order of VC > Cr₃C₂ > TaC. Cr₃C₂ addition would induce triangular prism grains and Co phase was strengthened by Cr₃C₂, resulting in the enhancement of transverse rupture strength (TRS) and impact toughness. WC morphologies in cemented carbides with VC addition were triangular prisms with multi-steps in basal and prismatic planes due to anisotropic growth. The multi-steps in basal and prismatic planes led to low TRS and fracture toughness. The inhibition mechanism of TaC is to reduce the surface energy of WC and slow down the solution/re-precipitation rate at the WC/Co interfaces by adsorbing on the surface of WC grains. The sample with 0.8 wt. % Cr₃C₂ had excellent comprehensive mechanical properties. Its Vickers hardness, fracture toughness, TRS and impact toughness were 1620 kg/mm², 9.94 MPa·m^1/2, 3960 MPa and 50.4 J/m², respectively. In summary, Cr₃C₂ is the first choice as the grain growth inhibitors (GGI) for the preparation of ultrafine cemented carbides.