Classification of Diamond Tool Materials

Diamond tool material is divided into single crystal diamond (natural and artificial, natural single crystal diamond is expensive, partially replaced by artificial single crystal diamond), artificial polycrystalline diamond (PCD) and artificial polycrystalline diamond and cemented carbide composite blades (PCD/CC) and CVD Diamond.

Single crystal diamond single crystal diamond used as a cutting tool must be large particles (mass greater than 0.1g, minimum diameter length not less than 3mm), mainly used for surface roughness, geometric accuracy and dimensional accuracy have higher requirements of precision and ultra Precision machining applications.

Natural single crystal diamond is the most wear resistant material in diamond. Its fine texture, finely ground, the radius of the cutting edge can be as small as 0.008 to 0.005μm. However, natural single crystal diamond is brittle, its crystal anisotropy, crystal hardness of different crystal faces or the same crystal face in different directions are all different, and the appropriate direction must be selected when grinding and using. Because of the harsh conditions of use, natural monocrystalline diamond resources are limited, and the price is very expensive. Therefore, PCD, PCD/CC, and CVD diamond tools are mostly used in production. Natural single crystal diamond is mainly used in the ultra-precision machining of certain non-ferrous metals or in the production of gold jewelry.

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

Artificial Polycrystalline Diamond (PCD) and Artificial Polycrystalline Diamond and Cemented Carbide Composite Inserts (PCD/CC)

PCD is a high-temperature (about 1800 °C), high pressure (5 ~ 6MPa), the use of cobalt and other metal binders to polycrystalline diamond crystal polycrystalline materials, its hardness is slightly lower than single-crystal diamond, but it is Randomly oriented diamond grains are polymerized isotropically and can be sharpened in any orientation when used as a cutting tool, eliminating the need to use the best cleaved face as a rake face for natural diamonds. During cutting, the cutting edge is very insensitive to accidental damage and has strong wear resistance. It can maintain a sharp cutting edge for a long period of time. It can use high cutting speeds and a large amount of back-feeding (eat deep) during machining. The service life is generally 10 to 500 times higher than that of the WC-based carbide tool, and because the metal binder in the PCD has conductivity, the PCD is easy to cut and formed, and the raw material source is rich. The price is only a few tenths of that of the natural diamond. Up to a dozen points have become a high-performance alternative to conventional WC-based carbide tools.

In order to improve the toughness and weldability of PCD inserts, a carbide composite substrate (PCD/CC) is formed by sintering or pressing a layer of 0.5 to 1 mm thick PCD on the surface of a cemented carbide substrate. PCD/CC can be used to make tools by welding or folder. Because of its good solderability, easy re-grinding, low cost, it is widely used. It should be pointed out that PCD and PCD/CC tools are not as sharp as the single-crystal diamond in terms of edge sharpness and machining surface quality. At the same time, they have poor machinability and a small grinding ratio. It is difficult to shape according to the geometry of the cutter head. Conveniently manufactured with geometrically complex products such as chipbreaker indexable inserts and end mills.

CVD diamond CVD diamond is a high wear resistant pure diamond material that does not contain binders and is prepared at low pressure (<0.1 MPa). CVD diamond is mainly in the form of CVD thin film coating (CD) and CVD thick film (TFD).

CD is a CVD (Chemical Vapor Deposition) process that deposits a layer of diamond-like diamond on a cemented carbide substrate (usually a K-type alloy) with a thickness of about 10-30 μm.

Because the base body is easy to make complex shapes, it is suitable for tools with complex geometric shapes, such as taps, drills, end mills and indexable inserts with chipbreakers. The international tool market has CD cutter products such as CD1810 from Swedish Sandvik Company and KCD25 from Kennametal Inc., USA. It is mainly used for high-speed precision machining of non-ferrous metals and non-metal materials, and has longer tool life than uncoated carbide tools. Increase nearly ten times or even dozens of times. However, CD cutters are not suitable for processing metals such as composites, because the hard particles in the composite material will wear through the coating on the surface of the tool in a short time, so although the price of CD cutters is lower than that of similar PCD cutters, However, due to the small adhesion between the diamond film and the base material, it has limited its wide application.