As CNC machine tools become the mainstream equipment for manufacturing equipment, in order to meet the requirements of CNC machine tools for high precision, high reliability, high processing efficiency, long life and environmental protection, it is particularly urgent to develop tools with excellent comprehensive performance. The development speed of tool materials can not meet the requirements of the tool. The surface modification of the tool can not only meet the requirements of different machine tools, but also reduce the pressure of developing new tool materials. Therefore, the tool surface modification engineering technology has been rapidly developed in recent years. development of.
At present, tool coating technology has been widely used in foreign industrialized countries and machinery processing industries, tool life has been significantly improved, and production efficiency and product quality have been greatly improved. China's imported tools, such as Sandvik, Kenner, Seco, Walter, Mitsubishi and other world-famous tool suppliers, almost all of their production tools are coated, so the application of tool coating technology is the future development of tools. Trends, while the development and application of high performance tool coatings is even more important.
Development history and current status of tool coating
1 History of tool coating development
The development and application of tool coatings has been nearly half a century old. In the early 1960s, Sweden's Sandvik and Germany's Krupp developed chemical vapor deposition (CVD) coating technology, which provided the first generation to the market in 1969. CVD coated carbide inserts. Since then, the United States, Japan and other countries have also introduced CVD coated carbide tools. With the continuous development of CVD technology and the improvement of equipment, the types of CVD coatings have developed in multiple, multi-layer and composite directions, which has greatly improved the performance of cemented carbide tools. Since the CVD coating process temperature is about 1000 ° C, although there is reliable film-based bonding strength, it also has some defects. For example, the cutting edge of the tool needs to be passivated, and the residual corrosion stress inside the tool coating is high. In addition, it can not be used for the surface coating of high-speed steel tools, which limits its application.
In the early 1970s, R.Bunshan and A.Raghuran developed the physical vapor deposition (PVD) coating technology. The deposition process temperature is below 500 °C, which is mainly used for surface coating of high speed steel tools. Over the years, with the continuous development of PVD process technology and the improvement of PVD equipment, its application fields have become more and more extensive.
2 Tool coating technology status
(1) CVD coating technology and development trends.
CVD technology is widely used in the surface treatment of cemented carbide inserts, enabling the deposition of single-layer coatings, single-component and multi-layer, multi-component composite coatings. The thickness of the coating can reach 7~9?m, which not only has good wear resistance, but also has high bonding strength with the substrate. However, due to the high temperature of the deposition process, the bending strength of the substrate is liable to decrease; the tensile stress inside the coating is high, which may cause microcracks during use. At the same time, the exhaust gas and waste liquid discharged during the CVD process are likely to cause environmental pollution.
At present, there are two main methods of CVD coating technology:
· The first method is a medium temperature CVD technique, which uses a C and N organic acetonitrile (CH3CN) as the main reaction gas and TiCl4, H2 and N2 to decompose and chemically react at 700 °C to 900 °C to form a new TiCN. The method can obtain a coating with a dense fibrous crystal form, and the coating thickness can reach 8-10 m. The coating structure has high wear resistance, thermal shock resistance and toughness, and can resist high temperature oxidation of Al2O3, TiN, etc. on surface deposition by HT-CVD (High Temperature Chemical Vapor Deposition) process technology, and A material with a low affinity for the material to be processed and a good self-lubricating property. MT-CVD coated inserts are suitable for high speed, high temperature, high load, dry cutting conditions, and their life is about 1 times higher than that of ordinary coated inserts.
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