Cucumber Boron Nitride (PCBN) for high-speed cutting in China was successfully developed in 1980 and polycrystalline diamond (PCD) in 1980. It has developed rapidly and can be used in various fields such as car, boring and milling. PCBN tools with different CBN content and PCD tools with different grain sizes. Among them, PCBN tools are mainly used for processing hardened steel, high-hard cast iron and some difficult-to-machine materials. PCD tools are mainly used for high silicon aluminum alloy processing. At present, superhard tools (PCBN, PCD and natural diamond ND), which are mainly researched and produced by many domestic joint ventures, dominate the market. Two types of tool applications are not yet common. Synthetic single crystal diamond and coated diamond are still under investigation.
Titanium carbide (TiC(N))-based hard alloys were developed in the late 1960s. The earliest TiC-based hard alloys have been developed. In recent years, TiC-TiN containing TiN and TiC(N)-based hard TiCN have been successfully developed. Several alloy products can be used for high speed precision and semi-finished steel, alloy steel and stainless steel of 200~400m/min. Recently, TiC+TiN nano-modified Ti(C,N)-based hard alloys with TiN nanopowders have been successfully developed in China. Tests have shown that processing 45 steel at a speed of 200 m/min is twice as long as that of a tool without nano-modification. There is currently no product. The main problem with Ti(C,N)-based tool materials is that there are fewer varieties and applications.
In the early 1970s, the company began to develop coated tools, initially developed CVD TiC single-coated hard alloys, and in the early 1980s studied PCD TiN single-coated high-speed steel tools. After years of hard work. A number of coating equipments have been imported from abroad. In recent years, CVD TiC-TiN, Al2O3-TiN multi-coated carbide inserts and PVD TiN, TiCN, TiAlN, TiAlCN composite multi-coated high-speed steel complex tools have been successfully developed. Low temperature (<600 °C) external thermal DC pulse plasma enhanced chemical vapor deposition (PCVD) technology has also been developed, with simple equipment, uniform coating thickness, high bonding strength, many types of coating materials, and no deformation of the workpiece. . However, the main products of coated tools on the market today are CVD Al2O3 and TiN composite coated carbide inserts and PVD TiN coated high speed steel tools. TiCN, TiAlN and TiAlCN commercial coating products are difficult to supply in time due to technical reasons, and there is still a gap between quality and foreign countries. PVD hard coatings such as carbon nitride (CNx), Al2O3, nitride [TiN(NbN), TiN/VN, etc.] and diamond PCD film coatings and soft coatings (MoS2, WS2) and nano-coatings are yet to be developed. . Foreign domestic agent companies are selling hot-selling coating tools, which has violently impacted the domestic market.
4 The future of high-speed cutting tool materials
The goal of ultra-high-speed cutting in the future is: milling aluminum is 10000m/min, cast iron is 5000m/min, ordinary steel is 2500m/min: drilling aluminum, cast iron and ordinary steel are 30,000, 20000 and 10000r/min respectively. Therefore, in the future, it is necessary to develop tool materials with superior high temperature mechanical properties, high chemical stability and thermal stability, and high thermal shock resistance.
PCD tools will continue to evolve and improve performance. They are widely used in the processing of aluminum alloys and high hardness non-metallic materials, but synthetic single crystal diamond and diamond thick film coatings will develop faster and will gradually replace PCD depending on their cost. In the field of high-speed ultra-precision mirror cutting, natural diamond tools still play an important role, but some will be replaced by artificial single crystal diamond. At present, the main reason for limiting the cutting speed of aluminum alloy machining by PCD tools is the spindle speed and power of the machine tool.
Al2O3 based and Si3N4 based ceramic tools and CBN tools are the preferred tool materials for high speed cutting of steel, cast iron and their alloys, but each has its scope of use and should continue to evolve. Al2O3-based ceramic tools have a wider application prospect for high-speed machining of steel and its alloys. Compared with CBN tools, it has both cost advantages and is suitable for processing hardened and unhardened steel and ferritic materials, but heat resistant. Sexual and thermal shock resistance is not enough. The development of nano-composite Al2O3-based ceramic knives with CBN added to the high temperature strength and thermal shock resistance of 1400-1500 °C is the main direction of the future. The development of Al2O3+Si3N4-based CBN composite tool materials with higher high-temperature strength and chemical stability in the field of high-speed processing of heat-resistant alloys is an important research direction.
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