Due to the hardness of the substrate and the coating, the modulus of elasticity and the coefficient of thermal expansion of the single-coated tool are far apart, and the lattice type is also different, resulting in an increase in residual stress and a weak bonding force. Adding new elements to the single coating (such as adding Cr and Y to improve oxidation resistance, adding Zr, V, B and Hf to improve wear resistance, adding Si to improve hardness and chemical diffusion resistance) to prepare a multi-tool coating material , greatly improving the overall performance of the tool.

The most common multi-tool coatings are TiCN, TiAlN coatings. The TiCN coating combines the good toughness and hardness of TiC and TiN coatings. It can control the properties of TiCN by continuously changing the composition of C and N during the coating process, and can form gradient structures of different compositions and reduce the coating. Internal stress, improve toughness, increase coating thickness, prevent crack propagation, and reduce chipping.

TiCN coating technology is constantly evolving. In the mid-1990s, the emergence of new technologies for medium temperature chemical vapor deposition (MT-CVD) revolutionized CVD technology. The MT-CVD technique uses organic acetonitrile (CH3CN) as the main reaction gas to form a TiCN coating below 700 °C. This TiCN coating method effectively controls the formation of very brittle η phase (Co3W3C) and improves the wear resistance, thermal shock resistance and toughness of the coating. Studies have shown that the appropriate increase of ion beam bombardment during PVD deposition of TiCN coating can also significantly improve the hardness and wear resistance of the coating. In recent years, TiCN-based quaternary component coating materials (such as TiZrCN, TiAlCN, TiSiCN, etc.) have also appeared.

TiAlN coating material is one of the most widely used high-speed carbide tool coatings. TiAlN has high high temperature hardness and excellent oxidation resistance. The coating composition is converted from the original Ti0.75Al0.25N to the preferred one. Ti0.5Al0.5N. The oxidation temperature of Ti0.5Al0.5N coating is 800 °C, and an amorphous Al2O3 film is formed on the surface during high speed processing to protect the coating. At present, research is focused on the improvement of TiAlN coatings to meet the increasing demands of applications such as oxidation resistance, thermal stability and thermal hardness. At present, CemeCon of Germany adopts high ionization sputtering technology (HIS®) to obtain advanced TiAlN coating. The coating has excellent adhesion to the substrate, avoiding the evaporation of the material in the molten state by the multi-arc ion plating technique. A phenomenon in which the form is deposited on the working surface, so that a very smooth and smooth coating on the surface can be obtained. Balzers' newly developed X.CEED coating is also a single layer of TiAlN coating with excellent red hardness and oxidation resistance, and the coating has good bonding strength with the substrate even under harsh conditions. Mitsubishi's MIRACLE coating is an Al-rich (Al,Ti)N coating that achieves direct processing of hardened steel by significantly increasing film hardness and oxidation resistance.

TiBN coating is a multi-component coating developed based on TiN and TiB2. It not only enhances the hardness of TiN coating, but also maintains good toughness, avoids brittleness of BN coating and TiB2 coating, and wear resistance of coated tool. And the corrosion resistance is significantly improved, and the friction coefficient is low. The bonding strength of the Ti-BN coating deposited by CHeau et al. on the sputtered Ti-B target was improved and the microhardness of 44 GPa was achieved. The TiAlBN coating developed by CemeCon Company produces a so-called "real-time" phenomenon in the process of boron by changing the boron content, that is, BN and B2N3 are formed by boron diffusion, thereby obtaining a lubricating film layer which is advantageous for cutting. In addition, there is a TiBON coating developed by Hitachi, which has a low coefficient of friction at high temperatures.

The Si element is added to the TiN to form a TiSiN multi-component coating, and its high temperature oxidation resistance is significantly improved compared with the single coating TiN. The TiSiN coating developed by Hitachi, Ltd. for hard cutting has a hardness of 36 GPa and an initial oxidation temperature of 1100 ° C. In addition, Hitachi has developed a lubricity with Cr instead of Ti, which is more suitable for bonding aluminum, stainless steel, etc. A highly abrasive material-processed CrSiN coating and a quaternary AlCrSiN coating with superior oxidation resistance.

Another representative multi-component coating from Balzers is an AlCrN coating that replaces Ti with Cr, called G6. The coating has a microhardness of HV3200 and can be used at temperatures up to 1000 ° C. Its toughness exceeds that of titanium. Coatings (such as TiAlN, TiCN) are more suitable for the processing of interrupted cutting and difficult-to-machine materials.

Chengdu Tool Research Institute has developed two series of high performance multi-component composite coatings of Ti-CNO-Al and Ti-CNB, which are the first in China. It has excellent composite mechanical properties and excellent cutting performance. It is mainly used in automotive cutting tools and Hertel. Series threaded comb blades. Other multi-coat materials include TiMoN, TiCrN, NbCrN, NbZrN and the like.

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