Surface-hardened gradient cemented carbide and preparation method thereof

The invention relates to the technical field of cemented carbide preparation, in particular to surface-hardened gradient cemented carbide and a preparation method thereof. By adjusting components of an alloy binding phase, the WC crystalline grains in the prepared cemented carbide are small, even in distribution, high in density and remarkable in gradient, the cemented carbide is made to have the more excellent mechanical property, and the red hardness of the cemented carbide is improved. The components and thickness of a gradient layer of the cemented carbide are controlled by adjusting blank formulas, sintering temperature, sintering time and other parameters, the surface layer of the cemented carbide is made to be rich in cubic phase and poor in binding phase, and due to the fact that a transition layer rich in alloying binding phase is arranged below the surface layer, the cemented carbide is excellent in hardness, wear resistance and roughness, and the cemented carbide can be used for metal machining. The cemented carbide prepared through the method has the excellent wear resistance, strength, hardness and toughness at the same time. According to the method, the functional gradient cemented carbide can be produced by slightly modifying existing equipment and processes, and is suitable for industrial production.