PCD is made of specially treated diamond sintered with a small amount of binder under high temperature and ultra-high pressure. The disorderly arrangement of diamond grains gives PCD a uniform, extremely high hardness and wear resistance. PCD can be used for cutting tools, grinding wheel dressing, geological drilling, gauging probes, wire drawing feelers, sandblasting feelers, etc. However, the high hardness and high wear resistance of PCD also pose great difficulties for its processing.

Scholars at home and abroad have conducted a lot of researches and tests on the processing problems caused by the high hardness and high wear resistance of PCD materials, including EDM, ultrasonic processing, electrochemical processing, laser processing, etc., and have achieved certain results. However, a comprehensive analysis shows that these machining techniques are mostly applicable to the rough machining of PCD materials at present. In order to obtain good quality of PCD cutting edge, the most ideal processing method is still grinding or lapping with diamond grinding wheels.

PCD grinding process is mainly the result of a mixture of mechanical and thermochemical effects. The mechanical effect is through the diamond wheel grinding grain on the PCD material of the continuous impact and the formation of diamond micro-breakage, wear, shedding or deconstruction; Thermochemical effect is the diamond wheel grinding PCD formed by high temperature to oxidation or graphitization of diamond. The mixture of the two results in the removal of PCD material. The grinding process is mainly characterized by the following

  (1) Grinding force is very high

  Diamond is the hardest known mineral material, and a variety of metal, non-metallic material pair friction wear amount is only 1/50 ~ 1/800 of carbide; PCD hardness (HV) for 80 ~ 120KN/mm2, second only to single crystal diamond, much higher than carbide. When using diamond grinding wheel to grind PCD, the starting cutting strength is very high, about 10 times higher than that of cemented carbide (0.4MPa); the specific grinding energy reaches 1.2×104~1.4×105J/mm3; Therefore, the grinding force is much higher than that of cemented carbide.

  (2) Small grinding ratio

  Due to the high hardness and wear resistance of PCD (the relative wear resistance is 16 to 199 times that of cemented carbide), the grinding ratio of PCD is only 0.005 to 0.033, which is about 1/1000 to 1/100000 of that of cemented carbide; the grinding efficiency is only 0.4 to 4.8mm3/min. Therefore, the grinding time is very long and the machining efficiency is very low in order to ensure the cutting tool edge quality and removal amount, The machining efficiency is very low. In addition, when the hardness, content and particle size of PCD are different, the grinding time also varies greatly.

(3)Grain size has a great influence

PCD material used for cutting tools is divided into three categories according to particle size: coarse (20-50μm), medium (10μm) and fine (~5μm), and the difference in grinding force and grinding ratio is several times to tens of times. Coarse-grained PCD have the highest grinding ratio and are the most difficult to grind, and have the most severe jagged edges and the worst quality after grinding, but the strongest wear resistance.