Polycrystalline diamond composite sheet having continuous gradient transition layer and preparation method thereof

A preparation method of a polycrystalline diamond composite sheet having a continuous gradient transition layer, comprising:

• mixing, granulating, and drawing sequentially a diamond micropowder and a binder A to obtain a diamond polymer composite filament material, wherein a particle size of the diamond micropowder is 1 to 100 μm;
• mixing, granulating, and drawing sequentially a WC powder, a Co powder, and a binder B to obtain a cemented carbide polymer composite filament material;
• putting the diamond polymer composite filament material and the cemented carbide polymer composite filament material into two feed inlets of a 3D printer respectively;
• controlling a feeding speed of the diamond polymer composite filament material and a feeding speed of the cemented carbide polymer composite filament material through a feeding system according to a model of the polycrystalline diamond composite sheet so that the diamond polymer composite filament material and the cemented carbide polymer composite filament material enter a mixing chamber individually or in different proportions;
• obtaining a polycrystalline diamond composite sheet green body after being extruded through a nozzle to perform deposition printing;
• and
• performing degreasing and synthesizing under a temperature of 1200° C. to 1800° C. and a pressure of 4 to 8 GPa on the polycrystalline diamond composite sheet green body to obtain the polycrystalline diamond composite sheet with a gradient structure,
• wherein the polycrystalline diamond composite sheet consists of a polycrystalline diamond layer, the continuous gradient transition layer, and a cemented carbide substrate from top to bottom, wherein the continuous gradient transition layer consists of diamond and cemented carbide, a content of the cemented carbide in the continuous gradient transition layer decreases from 100% to 0, and a content of the diamond increases from 0 to 100%, along a direction from the cemented carbide substrate to the polycrystalline diamond layer,
• wherein a mass ratio of the diamond micropowder and the binder A is 2:1 to 20:1;
• a composition of the binder A is, in terms of a mass percentage, as follows:
• 20 to 65% of ethylene-vinyl acetate copolymer, 5 to 35% of polystyrene, 5 to 35% of styrene-butadiene block copolymer, 3 to 10% of dodecyltrimethylammonium chloride, and 1 to 5% of oleic acid;
• and
• a diameter of the diamond polymer composite filament material is 1.65 to 1.85 mm.