Talking about the Development and Application of Tool Coating Technology

In the past 30 years, tool coating technology has developed rapidly and coated tools have been widely used. In 1969, Germany's Krupp and Sandvik developed a chemical vapor deposition (CVD) coating technology and introduced CVDTiC coated carbide inserts to the market. In the early 1970s, R. Runshan and A. Raghuran developed the physical vapor deposition (PVD) process and in 1981 introduced PVDTiN high speed steel tool products to the market. At that time, the CVD coating process temperature was about 1000 ° C, mainly used for the surface coating of cemented carbide tools (blades); PVD coating process temperature is 500 ° C and below 500 ° C, mainly used for surface coating of high speed steel tools.

Later, CVD and PVD coating technologies continued to develop rapidly, and great progress was made in coating materials, coating equipment and processes, and the coating technology of multilayer materials was developed to enable coated tools (blades). The performance has been greatly improved. PVD coating technology used to be mainly used for high speed steel tools. In recent years, with the rapid development of PVD coating technology, it has also been successfully used in cemented carbide tools (blades), occupying half of the positions of carbide coated tools (blades). . Nowadays, coated high speed steel tools and coated carbide tools (blades) are widely used, accounting for more than 50% of the total tool use.

Advantages of coated tools

Surface coating on a tough tool (blade) substrate, coating a thin layer (such as TiN, TiC, etc.) with high hardness, high wear resistance and high temperature resistance, so that the tool (blade) is comprehensive and good. Comprehensive performance. The hardness of uncoated high-speed steel is only 62~68HRC (760~960HV), the hardness of cemented carbide is only 89~93.5HRA (1300~1850HV); and the surface hardness after coating can reach 2000~3000HV.

1 Due to the high hardness and wear resistance of the surface coating material, and high temperature resistance. Therefore, compared to uncoated tools (blades), coated tools allow for higher cutting speeds, which improves machining efficiency; or increases tool life at the same cutting speed.

2 Since the coefficient of friction between the coating material and the material to be processed is small, the cutting force of the coating tool (blade) is smaller than that of the uncoated tool (blade).

3 It is processed with coated tools (blades), and the processed surface quality of the parts is good.

4 Due to the comprehensive performance of the coated tool (blade), the coated cemented carbide insert has better versatility, and a coated carbide grade insert has a wider range of use.

Development and advancement of tool coating technology

The author visited the International Machine Tool Exhibition for many times, collected a lot of materials, and listened to the technical reports of major tool companies to understand the development and progress of the surface coating technology of tool products.

Progress in CVD coating technology

In the past, the surface coating of cemented carbide tools was a high temperature chemical vapor deposition (HTCVD) process. In a normal or negative pressure deposition system, pure H2, CH4, N2, TiCl4, AlCl3, CO2 and other gases are uniformly mixed according to the composition of the deposit according to a certain ratio, and sequentially applied to a certain temperature (generally 1000) ~1050 ° C) cemented carbide blade surface, that is, deposited on the surface of the blade TiC, TiN, TiCN, Al2O3 or their composite coating. Until now, HTCVD is still the most used process. In addition to HTCVD, there is also a plasma chemical vapor deposition (PCVD) process, which is another method of coating the surface of cemented carbide tools (blades). The coating process temperature is low (700~800 °C), so the bending strength of the blade is reduced. Because TiC is the closest to the linear expansion coefficient of the matrix material, it is usually coated on the surface of the substrate with a thin layer of TiC, and then coated with TiN, Al2O3, such as TiC/TiN, TiC/Al2O3, TiC/TiCN/TiN, and the like.

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