Titanium alloy has good strength, toughness, ductility, and good oxidation resistance and corrosion resistance, so it is widely used in the fields of aerospace, automobile, chemical industry, and medical equipment.
Cutting tools are the key to realize high speed and high-efficiency machining of titanium alloy and coating technology has been widely used in cutting tools. The excellent coating can significantly improve tool surface performance, such as high-temperature hardness, thermal insulation, thermal stability, impact toughness, etc., so as to greatly improve cutting speed and life of cutting tools.
Titanium alloy cutting tool coating
Due to the high chemical activity and low thermal conductivity of titanium alloy, the cutting temperature is high, the chemical reaction is intense and the cutting tool quickly fails, which results in short tool life and high machining cost. The causes of tool wear include mechanical friction and physical and chemical reactions under the action of cutting force and cutting temperature. For the difficult machining of titanium alloy, the selected cutting tool material must meet the requirements of high hardness, high strength, high thermal conductivity, chemical stability, and red hardness. At present, the diamond cutter with the best effect of titanium alloy processing is recognized in the industry, but the carbide coated tool still occupies the main position in the titanium alloy cutting processing market because of the high price of diamond cutters.
According to the traditional cutting theory, the coated cutter cannot be used to process titanium alloy. This is because the traditional coating is mostly binary titanium carbide (TiC) or ternary titanium carbonitride (TiCN) coating, and the Ti element in the coating is easy to interact with the workpiece, resulting in rapid tool failure. However, the TC4 titanium alloy was machined by CrN and TiCN coating and uncoated tungsten-cobalt carbide cutting tools, and the results show that the service life of CrN coated cutter is longer than that of TiCN coated cutter and uncoated cemented carbide cutter.
Future development of cemented carbide coated tools
- Multi-component coating of tool
The multi-element coating material prepared by adding new elements into the single coating greatly improves the comprehensive performance of the cutter. Coating materials have also developed from TiN, TiAlN, and TiCN at the beginning to dozens of coating materials such as TiSiN, TiSiCN, TiAlSiN, AlCrN, AlCrSiN, TiBN, CrN and ZrN. There will be a great development prospect to meet the diverse needs of cutting.
- Greenization of the cutting
At present, wet cutting method is mainly used in machining, that is, when metal cutting, cutting fluid is used to continuously cool and lubricate the parts in contact with the workpiece. However, the use of a large number of cutting fluid will cause environmental pollution, and the cutting process of cutting fluid produced by lampblack direct harm to the human body, which is likely to cause a variety of diseases.
Moreover, cutting fluid accounted for 14%~16% of the total cost from the processing cost calculation, while the tool cost only accounted for 2%~4%. The results show that the total manufacturing cost can be reduced by 1.6% if the coating tool dry machining is used in 20% machining. High speed dry cutting can greatly improve the machining efficiency and precision, and reduce the surface roughness, so it is more suitable for machining thin wall parts.
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