Talking about the development and application of tool coating technology (2)

Later, multilayer coatings of various combinations were developed. The author has investigated and counted CVD coated cemented carbide inserts from various companies in Sweden, Germany, the United States, Japan, Korea, Israel and China at various exhibitions. The coating materials have the following combinations: TiCN/Al2O3, TiCN/TiC /TiN, TiCN/TiC/Al2O3, TiCN/Al2O3/TiN, TiCN/TiC/Al2O3/TiN, TiCN/Al2O3/TiCN, TiN, TiC/TiCN/TiN, TiN/TiCN/TiN, and the like. It can be seen that in recent years, TiCN or TiN has been used as the bottom layer. This is because the base cemented carbide has been improved. For example, a gradient structure is used to make it possible to use TiCN or TiN. In addition, the TiN coating should not be used alone because the hardness of TiN is not much improved compared with cemented carbide, and TiN must be used in combination with TiC, TiCN, Al2O3, and the like.

Progress in PVD coating technology

In the early days, the PVD coatings were all vacuum-evaporated. The layers were often uneven, and the bond with the substrate was not strong enough. After the development of the "vacuum magnetron sputtering method" and the "vacuum plasma plating process", the effect was very good. The latter two methods are mainly used for tool surface coating.

In the early years, PVD coatings were only used for high speed steel tools, and the coating material used almost exclusively TiN. Later, the coating process was improved, a variety of coating materials and multilayer coatings were developed, and a large number of applications were also applied to cemented carbide tools. The coating effect is much better than before. TiN coating materials are still in use, and the emerging coating materials are TiAlN and AlTiN, which are superior to TiN.

Europe has the highest level of PVD coating technology and is ahead of other countries and regions. Well-known manufacturers include Oerlkon Balzers, PVT Plasma Vacuum Technologies of Germany and Unimerco of Denmark. Their PVD coating equipment and process are advanced, with a wide range of coating materials, coating tools and other products with good performance.

Some well-known high-speed steel and carbide tool factories in foreign countries have coated tool (blade) products, but the coating equipment and processes are mostly purchased from or specialized in coating technology companies, rather than self-developed. It is reported that the PVD coating equipment of Sweden Sandvik and Israel Isca is purchased from Oerlikon Balzers. China should do the same, which is a good and fast road. For example, China Harbin No. 1 Tool Factory and German PVT Company established a Harbin Yipu Puwei Coating Cooperative Joint Stock Company. Oerlikon Balzers has 77 coating centers around the world, and a center in Suzhou, Tianjin and Hanjiang, China. Tool manufacturers in neighboring cities and regions in China, coating products are mostly coated at the above centers. The coating equipment of Hunan Zhuzhou Cemented Carbide Plant and Sichuan Zigong Great Wall Cemented Carbide Plant were imported from abroad.

Application of new CVD coating technology in super-hard material coating

A diamond film (10 μm) can be deposited on the surface of a cemented carbide or high speed steel tool by processes such as "hot wire CVD method", "plasma jet CVD method", and "flame combustion method". The mechanical and physical properties of CVD diamond films are between natural diamond and hot pressed polycrystalline PCD diamond, which can effectively process non-ferrous metals.

If the deposition time is increased, a thick film having a thickness of more than 0.5 mm can be deposited on the substrate or substrate (typically a silicon wafer). The thick film is peeled off from the substrate and cut into small pieces of a certain shape, and the small pieces are brazed on a base blade (generally a cemented carbide tool). CVD thick film diamond tools are used in a larger range than film coated tools. At CIMT2007, many domestic and foreign tool companies have CVD film diamond coated tool products, but only a few manufacturers have thick film products. Beijing Oriental Tiandi Superhard Material Tool Co., Ltd. can produce diamond thick film tool products and has many years of experience. Thick film cutters are used in a wide range of applications, including non-ferrous metals, non-metallic hard materials, and particle-reinforced composites.

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