Advantages of tool surface coating

- Dec 09, 2019-

Advantages of tool surface coating

At present, there are three key technologies in the field of cutting tool manufacturing: tool material, cutting process and coating technology. As one of the key technologies, coating technology can bring many advantages to cutting tools. The coating technology can greatly improve the surface hardness of the tool, make the tool have better wear resistance and cutting performance, reduce the friction coefficient with the workpiece, change the way of thermal diffusion to protect the tool matrix, improve the use efficiency and many other advantages.

Compared with uncoated blade, PCBN coated blade of our company has longer service life and can reduce cost and increase efficiency. With the same specification and material, at the same linear speed, feed speed and cutting depth, the cutting performance of coated PCBN blade is more stable than that of the original blade, with smaller size deformation, 2-3 times of the life of the original blade, and the wear of the blade is very small.

4. Tool coating material

Coating materials developed in the 1980s, generally divided into soft coating and hard coating materials. At present, the coating materials used for cutting tools are mostly hard coating materials, generally divided into silicide, boride, nitride, carbide, oxide, carbonitride, diamond and composite coating, a total of eight categories and dozens of varieties. Hard coating materials include single-layer films and composite films, mainly including: super hard coatings represented by diamond, TiSiN and tialsin, multilayer composite coatings such as tin / TiCN and Al2O3 / tin, compounds of multicomponent composite metals such as TiCN, TiAlN, tialcn and lubricating films, nitrides and carbides of transition metals such as tin, tic, ZrN and CrN.

Tic and tin coating materials have the earliest development and relatively mature application in industry. TiC coating has good mechanical wear resistance, which can reduce the resistance in the process of processing, reduce the cutting temperature, and has high hardness and wear resistance, but it is brittle and not resistant to impact. Tin material has high chemical stability, but its oxidation resistance is weak, its toughness and wear resistance are weak, its affinity with iron matrix is small, and its friction coefficient is low. Generally, the cutting temperature of tin is about 300 ℃. When the temperature reaches 500 ℃, the film has obvious oxidation and ablation.

TiCN has the characteristics of both tic and tin materials. It can reduce the internal stress of the coating, improve the toughness, increase the thickness of the coating, prevent the crack growth, reduce the chipping edge. It is suitable for the occasions requiring lower friction coefficient and higher hardness, such as the processing of ordinary steel, alloy steel, stainless steel and wear-resistant cast iron 

(Ti, Al) n will form a hard inert protective film composed of an amorphous alumina on the cutting edge interface when cutting. The film has poor thermal conductivity, which can make the chip take more cutting heat. (Ti, Al) n coating has good red hardness, oxidation resistance and low thermal conductivity. It has excellent neutral energy in high-speed cutting. It is more effective than tin in continuous high-speed turning, and also suitable for processing titanium alloy, nickel alloy stainless steel and other workpieces.

Compared with tic and tin coated tools, A12O3 coated tools have higher cutting performance. A12O3 has better chemical stability and high-temperature oxidation resistance in high-speed cutting of steel parts. The hardness reduction of A12O3 coating at high temperature is smaller than that of TiC coating, so it has better wear resistance and thermoplastic deformation resistance, and higher durability.

Diamond coating has excellent mechanical, thermal, optical and electrical properties, high modulus of elasticity and low coefficient of friction. It is suitable for high-speed cutting of non-ferrous alloys and has a wide application prospect. Research at home and abroad shows that diamond coated tools have been applied to the processing fields of graphite electrode, graphite mold, ceramic blank, aviation high silicon aluminum alloy, carbon fiber composite, mobile phone shell and parts, as well as other non-ferrous metal materials [7].

The pure diamond coated tool can not be used to process steel parts, because the cutting heat produced during the processing of steel parts leads to the chemical reaction of diamond into graphite, which destroys the adhesion layer between the coating and the tool.

Soft coating materials include: MoS2, WS2, cas2, tas2 / Mo, WC / C, etc. during machining, the coating can form a solid lubricating film on the tool surface, which makes the tool material have a very low friction coefficient. At present, there are few researches on soft coated tool technology in China. The application of soft coated tool in dry cutting can effectively prevent adhesion, reduce friction, reduce processing cost and improve tool life, which has great development potential.