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Do you know the material classification of diamond tools?

2020-04-22

Diamond tool materials are divided into single crystal diamond (natural and artificial diamond, natural single crystal diamond is expensive, partly replaced by artificial single crystal diamond), artificial polycrystalline diamond (PCD), artificial polycrystalline diamond and carbide composite blade (PCD/CC) and CVD diamond.


1. Single crystal diamond

As a cutting tool, single-crystal diamond must be of large particle size (mass > 0.1g, maximum path length not less than 3mm), mainly used in precision and ultra-precision machining applications where surface roughness, geometric shape accuracy and dimensional accuracy are highly required.

Natural single crystal diamond is the most wear-resistant material in diamond. It has a fine texture, and after fine grinding, the blunt circle radius of the cutting edge can be as small as 0.008~0.005 m. However, natural single crystal diamond is brittle, its crystal anisotropy, the hardness of different crystal faces or different directions of the same crystal face are different, so it is necessary to choose the right direction when grinding and using. Due to the harsh use conditions, and the limited natural single crystal diamond resources, the price is very expensive, so most of the production of PCD, PCD/CC and CVD diamond tools. The official account focuses on the important news of mechanical manufacturing and the sharing of relevant theoretical knowledge. The natural single crystal diamond is mainly used in the ultra-precision machining of some non-ferrous metals or the production of gold jewelry.

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


2. Synthetic polycrystalline diamond (PCD) and synthetic polycrystalline diamond and carbide composite blade (PCD/CC)

PCD is under high temperature (1800 ℃) and high pressure (5 ~ 6 mpa), the use of cobalt and other metallic bond will be a lot of polycrystalline diamond single crystal into polycrystalline material, its hardness is slightly lower than that of single crystal diamond, but it is a random orientation of aggregation of diamond grain, isotropic, used for cutting knife sharpening can be arbitrary orientation, without like natural diamond must choose good cleavage surface as the rake face. 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 cutter, and because the PCD in metal bond with electrical conductivity, making PCD facilitate cutting forming, and abundant raw material sources, its price is only a small percentage of natural diamond to one of the points, has become a high performance alternative to traditional the WC based cemented carbide cutter.

In order to improve the toughness and weldability of PCD blades, diamond composite blades (PCD/CC) are formed by sintering or pressing a layer of 0.5~1mm thick PCD on the surface of PCD blades with cemented carbide as the substrate. PCD/CC can be made by welding or clamping. Because its weldability is good, regrind is easy, cost is low, reason USES. It must be pointed out that both the sharpness of the cutting edge and the quality of the machined surface of PCD and PCD/CC cutter are inferior to that of single crystal diamond. Meanwhile, its machinability is poor, the grinding ratio is small, and it is difficult to form arbitrarily according to the geometric shape of the cutter head. Up to now, it is still not convenient to manufacture products with broken chip groove indexable blades and endmills with complex geometric shapes.



3. CVD diamond

CVD diamond is a kind of high wear resistance pure diamond material, it does not contain binder, it is prepared at low pressure (< 0.1MPa). CVD diamond mainly has CVD film coating (CD) and CVD thick film (TFD) two forms.

CD is formed by CVD (chemical vapor deposition) process and deposited a layer of film diamond with a thickness of about 10~30 m on the cemented carbide matrix (commonly used type K alloy).

Because the matrix is easy to be made into complex shape, it is suitable for tool with complex geometry, such as tap, drill, end milling cutter and indexable blade with broken chip slot. There are CD cutter products in the international tool market, such as CD1810 from Sandvik company in Sweden and KCD25 from Kennametal company in the United States, which are mainly used for high-speed precision processing of non-ferrous and non-metallic materials. The tool life is nearly ten times or even dozens of times longer than uncoated carbide cutter. However, CD cutter is not suitable for processing metal composite materials, because the hard particles in the composite will wear through a layer of coating on the surface of the cutter in a very short time. Therefore, although the price of CD cutter is lower than that of similar PCD cutter, the application of CD cutter is limited due to the small adhesion between diamond film and matrix material.




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