Hard alloy with gradient symmetrical structure and preparation method and application thereof

The preparation method comprises the following steps: preparing two parts of mixed powder A, two parts of mixed powder B and one part of mixed powder C, and paving the mixed powder C in the middle, the two parts of mixed powder B are respectively positioned on two sides of the mixed powder C and the two parts of mixed powder A are respectively positioned above or below the two parts of mixed powder B; the gradient powder is subjected to compression molding to obtain a pressed blank, and the pressed blank is sintered to obtain the hard alloy. The hard alloy provided by the invention has a gradient symmetrical structure, Co powder of different particles is adopted in each gradient layer for mutual matching, maximum stacking complementation among the particles is realized, the grain size and the microstructure of the sintered material and the Co diffusion degree are controlled by using the Co powder of different sizes, and the mechanical property of the material is controlled. The material performance is integra