The main performance of DLC film
1) mechanical properties
A. Hardness and elastic modulus. DLC films prepared by different deposition methods have great differences in hardness and elastic modulus. DLC films with hardness up to or even exceeding diamond can be prepared by magnetic filtration cathodic arc method. DLC films prepared by cathodic arc method have a maximum hardness up to 50GPa, while DLC films prepared by ion source combined with non-equilibrium magnetron sputtering method have a hardness up to 21GPa. The composition in the film layer has a certain impact on the hardness of the film layer. The incorporation of Si and N can improve the hardness of DLC film. DLC film has a higher elastic modulus, although lower than diamond (1100GPa), but significantly higher than the general metal and ceramic elastic modulus.
B. Internal stress and bond strength. The internal stress and bonding strength of the film are two important factors that determine the stability and service life of the film and affect its performance. DLC films with high internal stress and low bonding strength are prone to crack, fold and even fall off in application. Therefore, it is better to prepare DLC films with moderate compressive stress and high bonding strength. Most studies have shown that the film/base binding strength of DLC films deposited directly on the substrate is generally low. By adopting Ti/TiN/TiCN/TiC intermediate gradient transition layer, the bonding strength of DLC films and the substrate is improved. The bonding strength of DLC films deposited on the die steel is up to 44n-74n, and the overall thickness of the prepared film conductors is up to 5 microns.
2) friction DLC film not only has excellent wear resistance, but also has a very low friction coefficient, generally less than 0.2, is an excellent surface anti-wear modified film. The friction coefficient of DLC varies with the different preparation process and the change of the composition in the film, and the lowest friction coefficient can reach 0.005. Doping metal elements may reduce the friction coefficient, but adding H can improve the lubrication effect, and the environment also has a certain impact on the friction coefficient. However, in general, DLC film has obvious advantages in terms of friction coefficient compared with traditional hard films (such as TiN, TiC, TiAlN, etc.). The friction coefficient of these traditional hard films is above 0.4. In this country, DLC film is likely to replace these traditional hard films in many fields of tribology.
3) Because DLC is a metastable material, poor thermal stability is an important factor limiting the application of DLC film. When annealing at more than 300 degrees Celsius, sp3 bond changes to sp2 bond. Therefore, a lot of work has been done to improve its thermal stability. Some studies have found that the addition of Si can significantly improve the thermal stability of DLC film. DLC film containing 20% at%Si only shows the transformation from sp3 bond to sp2 bond when annealing at 740 degrees Celsius. Similarly, addition of metals (such as Ti, W, Cr) can also improve the thermal stability of DLC film, and we are conducting research in this regard.
4) corrosion-resistant pure DLC film has excellent corrosion resistance, which is difficult to be eroded by various acids, alkali and even aqua Regina. But DLC film doped with other elements has a reduced corrosion resistance, which is caused by the fact that doped elements are first eroded, thus damaging the continuity of the film.
5) the surface of DLC film is generally smooth and clean, which has no great influence on the surface smoothness of the substrate. However, as the film thickness increases, the surface smoothness will decrease. The surface finish of DLC film obtained by different deposition methods is also different, and the surface quality of DLC film deposited by ion source technology is obviously better than arc ion plating. DLC film has good adhesion resistance, especially for non-ferrous metals (such as copper, aluminum, zinc, etc.), and for plastics, rubber, ceramics, etc.
Application of DLC film in mechanical function field
1) DLC film of drill bit and milling cutter can be applied to drill bit and milling cutter, especially DLC film of doped metal, which not only has high hardness, but also has low friction coefficient and resistance to non-ferrous metal bonding. A metal-doped DLC film prepared by Hauzer of the Netherlands reduces so-called chip nodules (BUE) on the surface when cutting high-strength aluminum alloys. The result is a longer tool life and a smoother surface for the workpiece material after cutting. Especially in dry cutting and deep hole machining, the film performance is very good. Guangzhou institute of nonferrous metals has also carried out the TiAlN+DLC film plating on the milling cutter, significantly improving the service life and processing quality in the processing of nonferrous metals.
2) disc mould and its auxiliary mould disc mould is the important tool of production, the CDR, DVD CD, in order to reduce it and the motherboard (disc) of the friction, hope the mould surface hard and small friction coefficient, at present, foreign mostly adopts the DLC film layer, greatly improving the service life of mould and the quality of the disc, with the DLC film plated on its auxiliary mould, the life also has reached the requirement of supporting the use. After coating has high hardness, low friction coefficient, wear resistance, corrosion resistance, good adhesion and environmental protection and other characteristics. Disc die auxiliary die
3) the wear resistance, anti-friction and corrosion resistance of the core axle DLC film can significantly improve the service performance and service life of gear, core axle and other moving parts.
4) Now DLC is also applied to various blades, such as scissors and razors. DLC film reduces the friction between the blade and the skin, improves the performance of the blade and extends the service life.
5) The application of DLC film on key parts can also give play to its excellent performance in many key parts. For example, the application of DLC film on the piston of Stirling refrigerator can use its low friction coefficient to reduce friction, improve wear resistance, and meet the requirements of oil-free lubrication and service life. On the sewing machine accessories - hook DLC film to replace the original plating hard chromium plating processing, not only avoid the environmental pollution problem, and improve the surface hardness and wear resistance, service life is improved by more than 10 times, at the same time, also because of the lower friction coefficient, the surface coating layer in the process of the machine running noise smaller.
6) there are many other examples of DLC film application in industrial molds, such as: powder metallurgy moulds, plastic moulds, lead frame bending moulds, glass sheet moulds, magnesium alloy processing moulds, bearings, etc.
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