Polycrystalline Diamond (PCD) Cutting Tools

What is PCD?

History and Synthesis of PCD Material


Polycrystalline Diamond (PCD) was invented in 1971 by research scientists at General Electric. At the time, GE’s research team was looking for a material that could be used for cutting tools in a high-temperature, high-pressure environment. After years of research and experimentation, they succeeded in synthesising polycrystalline diamond, a synthetic superhard material with hardness and wear resistance similar to that of natural diamond.

General Electric research scientists Robert H. Wentorf Jr. and Dr. Francis P. Bundy were the principal inventors. They filed a patent application for polycrystalline diamond in 1971 and were successful in obtaining the patent. This invention caused a great sensation in the industry and became an important milestone in modern cutting tool technology. With the development and application of technology, polycrystalline diamond tools have become indispensable in many industries.


Polycrystalline diamond composite piece is to use cobalt as promoter, bond fine-grained diamonds on tungsten carbide or wrapped in it, put it into high-pressure device and heat it, and then form the composite after sintering, which is disorderly arrangement, non-directional, uniform hardness, lower hardness than natural diamonds (HV6000-8000 or so), high thermal conductivity coefficient (400-600W/mK), and low coefficient of thermal expansion (0.9×10), High abrasive elasticity and low coefficient of friction (0.1-0.3).

Polycrystalline diamond cutting tool material performance and characteristics.

Material properties

1. Hardness can reach 6000-8000HV, which is 5-6 times of tungsten steel.
2. The coefficient of thermal conductivity is (400-600W/mK), which is 1.5-9 times higher than that of tungsten steel and even higher than that of PCBN and copper, so the heat transfer is rapid.
3. The friction coefficient is only 0.1 to 0.3 (0.4 to 1 for tungsten carbide), which can significantly reduce the cutting force.
4. The coefficient of thermal expansion is only 0.9×10-6 ~ 1.18×10-6, only equivalent to 1/5 of tungsten carbide, so the thermal deformation of the tool is small and the machining accuracy is high.
5. Low affinity with non-ferrous and non-metallic materials, chips are less likely to stick to the tip of the tool and form an accumulation of chips during machining.
6. The sintered mass is isotropic and therefore less likely to crack along a single disintegrated surface.


Polycrystalline diamond composite piece is composed of tungsten steel base and polycrystalline diamond layer, the diamond content of polycrystalline layer is more than 90%, which has high hardness and abrasion resistance, and also has good impact resistance toughness. Compared with tungsten carbide tools, the hardness is 5~6 times higher; the cutting speed can be increased by 5-20 times; and the roughness can reach Ra0.05μm. It is mainly used for machining non-ferrous metal super-hard alloys, sintered tungsten carbide, aluminium alloys, copper, timber, plastics, glass fibre, acrylics, etc. The machined objects can reach a bright effect, and it can be used to make tools for turning, milling, planing, drilling, grinding, and lining, etc. The working life is much longer than that of tungsten carbide tools. The working life is 50~100 times longer than that of tungsten carbide tools, the cutting edge is not easy to be chipped and worn, and it is not easy to produce chip tumour, which can reduce the number of times of correcting on the tooling machine, and it is suitable for finish machining. It is the combination of diamond layer and tungsten carbide base to form the cutting tool material, which needs to be ground, polished, wire-cut and laser-cut before it can be used in all kinds of cutting tools.

Application of Polycrystalline Diamond Cutting Tools

Diamond is the hardest known substance in the world and is fully utilised in many industries and fields. At present, in the machining and machine tool industry, polycrystalline diamond is made into tooling used in machine tools, to solve some of the tungsten carbide (Tungsten carbide), cubic boron nitride tools (CBN/PCBN), ceramic tools, high-speed steel (HSS) cutting tools, etc. in the machining of workpieces required by the ultra-high surface brightness, finish, ultra-high precision, high hardness and other properties and difficult to machine the material. The polycrystalline diamond cutting tools are therefore known as super-hard cutting tools or diamond cutting tools in the machinery manufacturing industry.

Recommended Machining Parameters for PCD Materials

PCD Processing Parameter Reference

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