Trend of coatings of machining tools
The composition of coating will be diversified and compounded
The first generation PVD coating is mainly tin. On this basis, a variety of single metal coatings, such as tic, TiCN, ZrN, CrN, and WC, have been developed. With the further development of PVD deposition technology, aluminum element technology has been added to the coating. Aluminum containing multi-element metal alloy coatings, such as TiAlN and TiAlC, have come out one after another. Their wear resistance and red hardness are much higher than that of single metal coating. It can be used for higher cutting speed, such as rolling cutting, which can reach 150m / min. Later, it has become a trend that many different kinds of coatings are deposited on the tool layer by layer, such as TiN + TiCN + tin, Tin + TiAlN, TiAIN + WC / C, etc. In recent years, PVD coating technology has taken another step forward. Many foreign coating companies have developed and applied pulse coating technology, such as P3E (pulse enhanced electron emission) technology of Balzer's company in Switzerland and h.i.p. of German cemecon company_ (high ion pulse) technology. Both of these two new technologies use pulsed electron activated arc evaporation targets. Since the process can operate in an oxygen atmosphere, theoretically, almost any metal oxide (such as A12O3, ZrO2, Cr2O3, Ta2O5, etc.) and their compound coatings can be deposited by this process. At present, the Al2O3 coating has entered the practical test stage, and it is believed that it will be widely used in the near future.
Application and development of coating is more targeting
In order to meet different application requirements, the development and design of coatings are more and more targeted. According to the characteristics and requirements of different application fields, such as drilling, milling, dry rolling, stamping, drawing and so on, the coatings with comparative advantages are developed. After continuous efforts and attempts, it has been successful in some fields, such as the application of high aluminum content about tix (al: ti-2:1) coating in milling, AlCrN coating without Ti in high-speed dry rolling cutting, composite coating CrN + TiSiN in drilling, composite coating Tin + TCX applied in deep drawing die, the service life is obviously better than other coatings. In addition, various targeted coatings such as anti-corrosion (CrX coating), self-lubricating (WC / C coating), soft material processing (MoS2 coating), high hard material processing (CBN, diamond coating) have been widely used. Although these coatings are very successful in their respective fields, with the continuous development of PVD coating technology, new and more targeted coatings will continue to be developed to replace these existing coatings.
The deposition particles of the coating come into nano scale
With the development of nanotechnology and the progress of coating technology, nano tool coating has attracted the attention of researchers and PVD coating service companies. The nanoparticles can enhance the bonding strength between the coating and the substrate, and reduce the surface roughness of the coating. At present, the deposition particles of most coatings are still large. Although there are nanoscale coatings, large particles can still be found on the final surface of the coatings, and the coating surface is still rough. Reducing the size of coating particles and keeping the process stable to avoid the appearance of large abnormal particles will become another direction of coating development, especially in the application of the mirror surface. Although the limited company has developed mirror coating, its quality and stability are poor, and the process is also complex. In the future coating research and development, nano-coating particles and the thickness of the coating layer will be the main development direction, which is of great significance to improve the comprehensive performance of the coating, reduce the interlayer stress, and improve the surface finish, and further expand the wide application of the coating in the precision molding industry.
The process temperature of the coating is getting lower and lower
The deposition temperature of CVD coatings has been reduced from 1000 ℃ to 500 ℃ for PVD and PECVD coatings. Therefore, the application range of coatings has been expanded. However, the deposition temperature of 500 ℃ will still have adverse effects on the coated workpieces, such as deformation and matrix hardness reduction. Therefore, it is necessary to put forward special requirements for the pre-heat treatment of coated workpiece, such as the tempering temperature of the workpiece should not be lower than the coating temperature. The lower temperature coating, such as the coating temperature below 200 ℃, will eliminate these restrictions, make more kinds of materials available for coating, more flexible selection of early heat treatment, and more feasible comprehensive application of different surface modification technologies. At the same time, the application of low-temperature coating will also reduce the energy consumption of coating equipment, which has a certain environmental protection effect in energy saving. In addition, with the decrease of the coating temperature, the heating and cooling time will be reduced, and the delivery period of the coating will be shortened, and the efficiency will be higher. Therefore, the low-temperature coating will greatly promote the application and popularization of the coating and will become an important direction of the development of PVD coating.