Coated cutters are prepared by coating a thin layer of refractory metal or nonmetallic compound (or superhard material such as ceramic, diamond and cubic boron nitride) on the surface of hard alloy or high speed steel (HSS) matrix with good strength and toughness with vapor deposition method.As a chemical and thermal barrier, the coating reduces the diffusion and chemical reaction between the tool and the workpiece, thus reducing the matrix wear.Coated tool with high surface hardness, good wear resistance, stable chemical properties, heat resistance and oxidation resistance, small coefficient of friction and low thermal conductivity and other characteristics, cutting comparable to uncoated tool life increased 3~5 times, improve cutting speed 20%~70%, improve machining accuracy 0.5~1 level, reduce tool consumption cost 20%~50%.

     Coating materials must have high hardness, good wear resistance, stable chemical properties, not with the workpiece material chemical reaction, heat resistance and oxidation resistance, low friction factor, and with the matrix adhesion and other requirements.Obviously, a single coating material is difficult to meet the above requirements.Therefore, the hard coating materials have entered the new stage of developing thick film, composite and multi-coating from the initial application of single TiC, TiN and Al2O3.The newly developed composite coating of TiCN, TiAlN, TiAlN multielement, ultra-thin and ultra-multi-layer coating with TiC, TiN, Al2O3 and new anti-plastic deformation matrix has made great progress in improving the toughness of the coating, the bonding strength between the coating and the matrix, and the wear resistance of the coating.In addition, the technology of coating diamond film on hard alloy matrix is broken through, and the performance of cutting tool is improved comprehensively.

      The most mature process and the most widely used hard coating material is TiN, but TiN and matrix bonding strength is not as TiC coating, coating easy peeling, and hardness is not as high as TiC, in the higher cutting temperature when the film is easy to oxidation and ablation.TiC coating has high hardness and wear resistance, good oxidation resistance, but its brittleness, impact resistance.TiCN combines the advantages of TiC and TiN. It can control TiCN properties by continuously changing the components of C and N in the coating process, and form a multi-layer structure of different components, which can reduce the internal stress of the coating, improve the toughness, increase the thickness of the coating, prevent the propagation of cracks and reduce the crack breakage.Therefore, some of the blades produced, such as GC4000 series of blades recommended by Sweden's Sandvik company for steel processing, CN series of blades produced by China's zhuzhou cemented carbide plant, and T715X and T725X coated blades made by Toshiba of Japan all have TiCN coating components.TiCN base coating is suitable for processing ordinary steel, alloy steel, stainless steel and wear-resisting cast iron, etc.