Diamond tool materials are divided into single crystal diamond (natural and man-made, natural single crystal diamond is expensive, some of which are replaced by man-made single crystal diamond), man-made polycrystalline diamond (PCD), man-made polycrystalline diamond and carbide composite blade (PCD /CC), and CVD diamond.

Single crystal diamond

Single crystal diamond used as cutting tool must be large particle (the mass is more than 0.1g, the minimum path length is not less than 3mm), mainly used in precision and ultra-precision machining applications with high requirements for surface roughness, geometric precision and dimensional accuracy.

Natural single crystal diamond is the most wear resistant material in diamond. Its own fine texture, after fine grinding, cutting edge blunt circle radius can be as small as 0.008~0.005μm. However, natural single crystal diamond is brittle, its crystal anisotropy, different crystal surface or the same crystal surface of different directions of the crystal hardness are different, in grinding and use must choose the appropriate direction. PCD, PCD/CC and CVD diamond tools are mostly used in production due to the harsh conditions and limited natural single crystal diamond resources. Natural single crystal diamond is mainly used in ultra-precision cutting of some non-ferrous metals or in the production of gold jewelry.

The size, shape and performance of synthetic single crystal diamond have good consistency. At present, due to the increasing maturity of high temperature and high pressure technology, synthetic single crystal diamond of a certain size can be prepared, especially in the processing of high-wear laminated wood, its performance is better than PCD diamond, will not cause premature passivation of cutting edge.

Synthetic polycrystalline diamond (PCD) and synthetic polycrystalline diamond and carbide composite blades (PCD /CC)

PCD is a polycrystalline material made of many diamond single crystal powders by cobalt and other metal bonding agents at high temperature (about 1800℃) and high pressure (5~6MPa). Although the hardness of PCD is slightly lower than that of single crystal diamond, it is the polymerization of randomly oriented diamond grains, which is isotropic and can be used as a cutting tool for grinding with arbitrary orientation. It is not necessary to choose the best cleavage surface as the cutting surface as natural diamond. In cutting, the cutting edge of accidental damage is not very sensitive, the wear resistance is strong, can maintain sharp cutting edges, for a long time when processing can use high cutting speed and a larger quantity of turning (deep), the service life of the general 10 ~ 500 times higher than the WC based cemented carbide cutting tools, and because the PCD in metal bond with electrical conductivity, It makes PCD easy to cut and form, and the raw material source is rich. Its price is only a tenth to a tenth of the natural diamond, and it has become a high-performance substitute for traditional WC based carbide tool.

In order to improve the toughness and weldability of PCD blade, diamond composite blade (PCD/CC) is composed by sintering or pressing a layer of 0.5~1mm thick PCD on the surface of cemented carbide base. PCD/CC can be made by welding or clamping. Because of its good solderability, easy regrinding and low cost, it is widely used. It should be pointed out that the edge sharpness and machining surface quality of PCD and PCD/CC tools are not as good as that of single crystal diamond. At the same time, the machinability of PCD and PCD/CC tools is poor, the grinding ratio is small, and it is difficult to form arbitrarily according to the geometric shape of the tool head. So far, it is not easy to manufacture the products with complex geometric shapes, such as the indexable blade with chip slot and the end mill.

CVD diamond

CVD diamond is a pure diamond material with high wear resistance without binder. It is prepared at low pressure (< 0.1mpa). CVD diamond mainly has two forms: CVD film coating (CD) and CVD thick film (TFD).

CD is composed of polycrystalline diamond-like film with a thickness of 10~30μm deposited on a hard alloy matrix (commonly used as class K alloy) by CVD (chemical vapor deposition) process.

Because the matrix is easy to be made into complex shapes, it is suitable for cutting tools with complex geometric shapes, such as taps, drills, end mills and indexable blades with chip slots, etc. CD tools are available in the international tool market, such as CD1810 from Sandvik Company in Sweden and KCD25 from Kennametal Company in the United States. They are mainly used for high-speed precision machining of non-ferrous metals and non-metallic materials. The tool life is nearly ten times or even tens of times higher than that of uncoated cemented carbide tools. But CD tool is not suitable for processing metal type of composite materials, because the composites of hard particles in a very short period of time will be grinding tool surface a layer of coating to wear, so although CD tool is lower than congener PCD cutting tools, but due to the adhesion between the diamond film and the substrate material smaller, thus limits its wide application.