Diamond tools are mostly used for fine cutting and boring of non-ferrous metals and non-metallic materials at high speed. It is suitable for processing various wear-resistant non-metals, such as FRP powder metallurgy blanks, ceramic materials, etc.; various wear-resistant non-ferrous metals, such as various silicon-aluminum alloys; various non-ferrous metal finishing processing.

The disadvantage of diamond tools is that they have poor thermal stability. When the cutting temperature exceeds 700°C to 800°C, it will completely lose its hardness; in addition, it is not suitable for cutting ferrous metals, because diamond (carbon) is easy to bond with iron at high temperatures. The atomic action converts the carbon atoms into a graphite structure, and the tool is easily damaged.

Cubic boron nitride (CBN), the second superhard material synthesized by a method similar to that of diamond, is second only to diamond in terms of hardness and thermal conductivity. It has excellent thermal stability and can be heated to 10,000°C in the atmosphere. Oxidation does not occur. CBN has extremely stable chemical properties for ferrous metals and can be widely used in the processing of steel products.

Cubic boron nitride (CBN) is a substance that does not exist in nature. It can be divided into single crystal and polycrystalline, namely CBN single crystal and polycrystalline cubic boron nitride (PCBN). CBN is one of the isomers of boron nitride (BN), and its structure is similar to that of diamond.

PCBN (polycrystalline cubic boron nitride) is a polycrystalline material that sinters fine CBN materials through a bonding phase (TiC, TiN, Al, Ti, etc.) under high temperature and high pressure. Diamond tool material, it and diamond collectively referred to as superhard tool material. PCBN is mainly used to make knives or other tools.

PCBN tools can be divided into integral PCBN blades and PCBN composite blades sintered with cemented carbide.

PCBN composite inserts are made by sintering a layer of PCBN with a thickness of 0.5 to 1.0mm on a cemented carbide with good strength and toughness. Its performance has both good toughness and high hardness and wear resistance. The problems of low bending strength and welding difficulties of CBN inserts are solved.

Although the hardness of cubic boron nitride is slightly inferior to diamond, it is much higher than other high hardness materials. The outstanding advantage of CBN is that its thermal stability is much higher than that of diamond, which can reach above 1200°C (700-800°C for diamond). reaction. The main performance characteristics of cubic boron nitride are as follows.

① High hardness and wear resistance: CBN crystal structure is similar to diamond, and has similar hardness and strength to diamond. PCBN is especially suitable for processing high-hardness materials that could only be ground before, and can obtain better surface quality of workpieces.

② High thermal stability: The heat resistance of CBN can reach 1400-1500°C, which is almost 1 times higher than that of diamond (700-800°C). PCBN tools can cut high-temperature alloys and hardened steels at a speed 3 to 5 times higher than that of cemented carbide tools.

③Excellent chemical stability: It does not have chemical interaction with iron-based materials at 1200-1300°C, and it will not wear out as sharply as diamond, and it can still maintain the hardness of cemented carbide at this time; PCBN tools are suitable for cutting hardened steel Parts and chilled cast iron, can be widely used in high-speed cutting of cast iron.

④ Good thermal conductivity: Although the thermal conductivity of CBN is not as good as that of diamond, the thermal conductivity of PCBN is second only to diamond among various tool materials, and is much higher than that of high-speed steel and cemented carbide.

⑤ Has a low coefficient of friction: a low coefficient of friction can reduce the cutting force during cutting, reduce the cutting temperature, and improve the quality of the processed surface.

Cubic boron nitride is suitable for finishing various difficult-to-cut materials such as hardened steel, hard cast iron, superalloy, hard alloy, and surface spraying materials. The machining accuracy can reach IT5 (the hole is IT6), and the surface roughness can be as small as Ra1.25～0.20μm.

The cubic boron nitride tool material has poor toughness and bending strength. Therefore, cubic boron nitride turning tools are not suitable for rough machining with low speed and high impact load; Severe built-up edge will occur in the case of metal, which will deteriorate the machined surface.