With the development of nanotechnology and advances in coating technology, nano-tool coating materials have also attracted the attention of researchers. There are two main types of nano-coatings: nano-multilayer structures and nano-composite structures. Nano-multilayer coatings generally consist of a high-rise number of structural materials, chemical bonds, and single-layer materials with atomic radii and lattices that are often close together, and may result in a new coating that is significantly different from the performance of the individual coatings that make up it. . This is an artificially controllable one-dimensional periodic structure with alternating deposition of a single layer coating of no more than 5 to 15 nm. Chu and Barnett believe that the high hardness of nano-multilayer coatings is mainly due to the difficulty of movement of layers or interlayer dislocations. When the coating is very thin, the shear modulus between the two layers is different. If the dislocation energy of the interlayer is greatly different, the interlayer dislocation motion is difficult, that is, the energy of the dislocation motion determines the hardness of the superlattice coating. . The structure of the nano-multilayer coating is mainly in three ways: (1) alternating coating of metal nitride nano-layer and metal AlN nano-layer; (2) alternating coating of metal AlN nano-layer and metal AlCN nano-layer; (3) metal nitrogen The nano layer of the compound is alternately coated with the metal AlN nano layer and the metal AlCN nano layer. Other metal elements (such as titanium, tantalum, niobium, vanadium, niobium, zirconium or chromium) may be added during the coating process to further improve the hardness, chemical stability, toughness and oxidation resistance of the coating. Studies have shown that for TiN/AlN nano-multicoating, when the layer thickness is 2~4nm, AlN exhibits cubic NaCl structure, the microhardness of the coating reaches 30~40GPa, and its oxidation temperature reaches 1000°C, using plasma enhanced chemical vapor phase. The deposited AlN/TiAlN nano-multilayer film has high hardness, high adhesion and high wear resistance.

Although nano-multilayer coatings achieve higher hardness, studies have shown that the performance of nano-multilayer coatings is highly dependent on the periodic film thickness of the coating, when nano-multilayer films are deposited on the surface of complex shaped tools or parts. It is difficult to control the film thickness of each layer, and at the same time, the interdiffusion of elements between layers in a high temperature working environment may also cause a decrease in coating performance, and a single layer nanocomposite coating can solve these problems. German material scientist Veprek et al. proposed the theory and design concept of nanocomposite superhard coating according to Koehler's theory of epitaxial heterostructure, and Ti-Si-N (nc-TiN/) prepared by plasma enhanced chemical vapor deposition. It has been confirmed in the a-Si3N4) system that both nc-W2N/a-Si3N4 and nc-VN/a-Si3N4 also exhibit good mechanical properties. Nanocomposite superhard materials represented by nc-TiN/a-Si3N4 have attracted great interest due to their excellent properties such as ultra-high hardness, high hardness, high toughness and low friction coefficient. Zhang deposited the nc-TiN/a-Si3N4 nanocomposite coating with ion beam and systematically studied its microstructure, surface morphology and mechanical properties. The results show that the composite coating reaches a maximum of 42 GPa at a Si content of 11.4%. Kim et al. studied closed-field unbalanced magnetron reactive sputtering of TiAlSiN coatings consisting of nanocrystalline TiAlN and amorphous Si3N4 with microhardness and elastic modulus of about 42 and 490 GPa. Nakonechan et al. prepared a (Ti, Si, Al) N coating with a cathodic arc PVD with a maximum hardness of 38 to 39 GPa. Ribeiro et al studied the effect of ion bombardment on the (Ti, Si, Al)N coating. It was found that TiAlN and SiNx phases existed in the system, and nc-TiN/a-Si3N4 composite nanostructures were formed. The increase of ion bombardment can increase the hardness. 30GPa is increased to 45GPa.

Although most of these nanostructured coatings are the result of the laboratory, the results show a good prospect for nanostructured coatings in metal cutting.

The ACXG, AC110G and other grades of ZX coating developed by Sumitomo Corporation of Japan are nano-multilayer coatings with alternating TiN and AlN. The number of layers can reach 2000 layers, and the thickness of each layer is about 1 nm. The new coating has high bonding strength with the substrate, the coating hardness is close to CBN, the oxidation resistance is good, the peeling resistance is strong, and the surface roughness of the tool can be significantly improved, and the service life is 2 to 3 times that of the TiN and TiAlN coating. FUTUNANANO and FUTUNATOP, developed and used by Balzers, are two TiAlN nanostructured coatings with an average hardness of HV3300 and an initial oxidation temperature of 900 °C. Platit, Switzerland, developed a nano-multilayer coating with AlN as the main layer and TiN-CrN as the intermediate layer, which alternated to form a multilayer structure. Tests have shown that the hardness of the coating is highest at a cycle of 7 nm, about 45 GPa. The company's new generation of nc-TiAlN/(a-Si3N4) nanocomposite coatings developed using LARC® (Lateral Rotating ARC-Cathodes) technology is a 3 nm TiAlN crystal embedded in amorphous Si3N4 under strong plasma. The structure is 1 nm thick Si3N4 between the crystal grains. This structure makes the coating hardness 50 GPa, and the high temperature hardness is very prominent. When the temperature reaches 1200 ° C, the hardness value can be maintained at 30 GPa. Hitachi recently developed a TH coating (TiSiN) made of nanocrystalline material to achieve high temperature and high hardness. From high-precision machining of pre-hardened steel to hardened steel, it has remarkable advantages in high-efficiency processing. It is more than twice as high, and it is most suitable for dry milling because it is resistant to high temperatures during cutting. At the same time, Hitachi has also developed a CS coating (CrSiN) with a nanostructure suitable for the processing of mild steel. The "IMPACTMIRACLE end mill" produced by Mitsubishi Materials Kobe Tools uses advanced single-phase nanocrystalline (Al, Ti, Si) N coating with an oxidation temperature of 1300 ° and a bonding force of 100 N to the substrate. When the high-hardness material is left and right, the life of the tool can be greatly extended.

Cemecom's new nanostructured Supernitrides coating contains high levels of elements that produce different oxides. These coatings combine the excellent wear resistance of hard coatings with the chemical stability of conventional oxide coatings to provide excellent thermal and chemical stability in applications. The morphology and composition of the coating (eg, aluminum content, structure, surface finish, etc.) can be optimally designed for the application. The results of drilling, milling, hobbing and turning tests on a variety of different materials (eg CGI, 42CrMo4, cast iron, tool steel, etc.) confirm the superior performance of the Supernitrides coating.