PCD material grinding characteristics
Apr 10, 2020

PCD is made by sintering specially treated diamond and a small amount of binder under high temperature and high pressure. The disorderly arranged diamond grains give PCD a uniform, extremely high hardness and wear resistance. PCD can be used for cutting tools, grinding wheel dressing, geological drilling, measuring tool probes, wire drawing tools, sandblasting tools, etc. However, the high hardness and high wear resistance of PCD also bring great difficulties to its processing.

Scholars at home and abroad have conducted a lot of research and experiments on the processing difficulties caused by the high hardness and high wear resistance of PCD materials, including electrical discharge machining, ultrasonic machining, electrochemical machining, laser machining, etc., and have achieved certain results . However, comprehensive analysis found that these processing techniques are currently mostly suitable for rough machining of PCD materials. In order to obtain good PCD cutting edge quality, the most ideal processing method is still grinding or lapping with diamond wheels.

The grinding process of PCD is mainly the result of the mixed action of mechanical and thermochemical aspects. The mechanical action is the micro-breaking, abrasion, shedding or cleavage of the diamond formed by the continuous impact of the diamond wheel abrasive particles on the PCD material ; the thermochemical action is the high temperature formed by the diamond wheel grinding the PCD to oxidize or graphitize the diamond. As a result of the mixed action of the two, the PCD material was removed.

The characteristics of its grinding process are:

(1) Great grinding force

Diamond is the hardest substance among the known minerals, and the wear amount of friction with various metal and non-metal materials is only 1/50 ~ 1/800 of cemented carbide; PCD hardness (HV) is 80 ~ 120KN / mm2 , Second only to single crystal diamond, much higher than cemented carbide. When the diamond grinding wheel is used to grind PCD, the initial cutting strength is very high, which is about 10 times more than that of cemented carbide (0.4MPa); the specific grinding can reach 1.2 × 104 ~ 1.4 × 105J / mm3; therefore, the grinding force is much higher Used for grinding cemented carbide.

(2) The grinding ratio is very small

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

(3) Granularity has great influence

PCD materials are used for cutting tools according to particle size. They are mainly divided into three categories: coarse particle size (20-50 μm), medium particle size (about 10 μm) and fine particle size (~ 5 μm). The grinding force and grinding ratio are several times to tens of different. Times. Coarse-grained PCD has the highest grinding ratio, and grinding is also the most difficult. After the grinding, the cutting edge is the most serious and the quality is the worst, but the wear resistance is strongest; the fine-grained PCD grinding ratio is relatively lowest, and the grinding is easier. The best cutting edge quality after grinding

PCD material tools

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