Multilayer gradient polycrystalline diamond compact and preparation method thereof

The invention belongs to the technical field of superhard materials, and particularly relates to a multilayer gradient polycrystalline diamond compact and a preparation method thereof. The multilayer gradient polycrystalline diamond compact comprises a polycrystalline diamond layer, a transition layer A, a hard alloy layer, a transition layer B, a polycrystalline diamond layer, a transition layer C and a hard alloy matrix which are arranged in sequence. On the basis of adopting a double-edge structure and inheriting high wear resistance and impact resistance of a traditional PDC composite sheet, through the gradient structure design of the multiple transition layers, residual stress between the hard alloy layer and the polycrystalline diamond layer is greatly reduced, the risk of cracking of the polycrystalline diamond layer is reduced, and the service life of the polycrystalline diamond layer is prolonged. Meanwhile, the bonding strength between the hard alloy layer and the polycrystalline diamond layer is g