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Polycrystalline diamond compact (PDC) is a superhard composite material made from diamond powder as raw material, WC cemented carbide as matrix, and sintered under high-temperature and high-pressure conditions through a specific synthesis process. PDC cutters have the advantages of high diamond hardness, good wear resistance, and strong impact resistance of hard alloys. They have now expanded from the use of deep well drilling to various fields such as mineral exploration and mechanical processing. Wear resistance, as an important characteristic of PDC cutters use, is generally characterized by the wear ratio parameter. PDC cutters manufacturers are striving to improve their wear resistance as much as possible. However, due to the many factors that affect the wear resistance of PDC cutters and their mutual constraints, there are still some problems in further improving the wear resistance of PDC cutters;
Polycrystalline diamond composite have both the extremely high wear resistance of polycrystalline diamond and the high impact resistance of hard alloys. The diamond layer has a sharp and self sharpening edge, which can always maintain the sharpness of the cutting edge. Therefore, it is very suitable for exploration in soft and medium hard formations in petroleum and geological drilling, with very good results. The diamond content in polycrystalline diamond compact is as high as 99%, so the diamond layer has extremely high hardness and excellent wear resistance, with a Rockwell hardness of 6.5104~7.0104 MPa or even higher. The hard alloy matrix overcomes the shortcomings of hard and brittle polycrystalline diamond, greatly improving the overall impact toughness of the product. The weldability of hard alloys solves the problem of difficulty in combining polycrystalline diamond with other materials through welding methods, allowing polycrystalline diamond composite sheets to be vertically embedded and welded onto the drill bit.
The main characteristics of PDC cutters are as follows:
1) Has extremely high hardness. The hardness of polycrystalline diamond ranges from HV7500 to 9000, second only to natural diamond. Due to its high toughness of hard alloy support, its composite bending strength can reach 1500MPa.
2) Has high wear resistance. The wear resistance of polycrystalline diamond is generally 60-80 times that of hard alloy. When cutting non-metallic materials with high hardness (> HV1500), the durability is extremely high.
3) Has a lower coefficient of friction. The friction coefficient between polycrystalline diamond and non-ferrous metals is 0.1-0.3, while the friction coefficient between hard alloy and non-ferrous metals is 0.3-0.6. PCD tools made of polycrystalline diamond (PCD) material can reduce cutting force and cutting temperature by about 1/2-1/3 compared to hard alloy tools.
4) Has high thermal conductivity. The thermal conductivity of polycrystalline diamond is 1.5-7 times that of hard alloy, which can greatly reduce the temperature in the cutting zone and improve tool durability.
5) Has a small coefficient of expansion. The linear expansion coefficient of polycrystalline diamond is very small, about 1/10 of that of ordinary steel. In addition, due to the sharp edge of the cutting tool, the degree of work hardening on the machined surface is only about one-third of that of hard alloy cutting tools, so the machining accuracy is good.
6) It can be made into various sizes and shapes as needed.
7) It exhibits significantly superior toughness and impact resistance compared to single crystal diamond, which to some extent compensates for the shortcomings of high brittleness and easy cleavage fracture of single crystal diamond.