Method for preparing gradient hard alloy by directly adding refractory metal

The invention relates to a method for preparing a gradient hard alloy by directly adding refractory metals, belonging to the field of hard alloy material preparation. The method comprises the following steps: molding carbon-poor hard alloy powder containing refractory elements, performing vacuum sintering so as to obtain a carbon-poor pre-sintered substrate, and performing carburizing treatment for 40-240 minutes at 1400-1460 DEG C in the hydrogen atmosphere, thereby obtaining the gradient hard alloy. As the refractory elements are directly added, a function of inhibiting WC crystal grains from growing up is achieved in the sintering process; in the carburization process, the refractory elements are reacted with activated carbon, and meanwhile the generated refractory metal carbide has a relatively large inhibition function on carburization reaction, so that the gradient layer formation speed is reduced. By appropriately prolonging the carburization time, the problem caused by reduction of the gradient layer formation speed is reduced is solved, the carburization reaction can be performed relatively sufficiently, the content of Co on a surface layer is relatively low, and the purpose of improving the high alloy property is achieved.