Research progress of cutting tool coating technolo

2022-06-14
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Research progress of cutting tool coating technology

the surface coating technology of cutting tools (coated cemented carbide and coated high speed steel tools) is a material surface modification technology developed in response to the market demand in recent decades. The use of coating technology can effectively prolong the service life of cutting tools and give them excellent comprehensive mechanical properties, so as to greatly improve the machining efficiency. Because of this, coating technology, cutting materials and machining technology are called the three key technologies in the field of cutting tool manufacturing

cutting tool coating refers to coating a layer of material with high hardness and wear resistance on the surface of mechanical cutting tools. In order to meet the requirements of modern machining for high efficiency, high precision and high reliability, the manufacturing industry all over the world pays more and more attention to the development of coating technology and its application in tool manufacturing. In the factories of industrial developed countries, the coated tools account for nearly 60% of the total

sec duratomic coating cross section

at present, the coating technology methods mainly include vapor deposition method, sol-gel method, thermal spraying method, etc. Among them, vapor deposition is widely used, and the quality of the coating is high. Vapor deposition technology can generally be divided into physical vapor deposition (PVD, see Figure 1 for equipment) and chemical vapor deposition (CVD, see Figure 2 for equipment)

Figure 1 physical vapor deposition equipment

Figure 2 chemical vapor deposition equipment

the methods of preparing cutting tool surface coating by vapor deposition mainly include the following: magnetron sputtering deposition coating, arc ion plating deposition coating, high temperature chemical vapor deposition coating, medium temperature chemical vapor deposition coating and plasma enhanced chemical vapor deposition coating. Among them, the most commonly used are high-temperature chemical vapor deposition, magnetron sputtering deposition and arc ion plating. The advantages and disadvantages of various coating technologies will be described in combination with the different mechanisms of various coating technologies

magnetron sputtering deposition technology

magnetron sputtering coating technology belongs to the category of glow discharge, which uses the principle of cathode sputtering for coating. The film particles come from the cathode sputtering effect of argon ions on the cathode target in glow discharge. The target atoms are sputtered by argon ions and deposited on the workpiece to form the required film. Because the magnetic field is introduced into the target part of the sputtering device, the magnetic lines of force confine the electrons near the target surface and prolong their trajectory in the plasma, so as to improve their participation in the process of gas molecule collision and ionization

magnetron sputtering deposition has the following advantages: (1) high deposition rate and low target voltage required to maintain discharge; (2) The bombardment energy of electrons on the substrate is small; (3) The film structure is fine. Because the magnetron sputtering deposited coating is atomic particles obtained by cathode sputtering, it carries the high energy obtained from the target surface to the workpiece, which is conducive to form a fine core and grow into a very fine film structure; (4) Magnetron sputter deposited coatings can obtain large-area films and can be widely used

however, this method also has the following problems: (1) uneven etching of the target. Due to the uneven distribution of magnetic field intensity, the utilization rate of target is low. This can be operated by closing the mouse; The structure of the target is designed, and the electromagnetic field is added to promote the change of the magnetic field intensity on the target surface, so as to realize the discharge scanning, so as to effectively improve the utilization rate of the target. (2) Low metal ionization rate. In view of this, the volume of the magnet in the center of the target can be increased (or reduced) as required, causing some magnetic lines of force to diverge near the substrate far away from the target, so as to achieve unbalanced magnetron sputtering

it is worth mentioning that magnetron sputtering can also be used to prepare multilayer and nano films. With the rapid development of high and new technology and emerging processing industry, the demand for depositing multilayer and nano films with higher performance is increasing. Therefore, magnetron sputtering technology is worthy of further research and development, and its application prospect is superior

arc ion plating deposition technology

ion plating (IP) is a new technology developed on the basis of vacuum evaporation. It introduces various gas discharge modes into the field of vapor deposition, so that the whole vapor deposition process is carried out in plasma. Among them, arc ion plating (AIP) belongs to the category of cold field arc discharge. It is a solid-state evaporation source without fixed molten pool. Circular cathode arc source is mostly used as the evaporation source

The advantages of

AIP are: (1) high metal ionization rate, up to 60% ~ 90%; (2) The deposition rate of arc ion plating is high; (3) The film base adhesion of the deposited coating is good; (4) It is easy to obtain titanium nitride and other compound coatings, and has also achieved gratifying results. Mass production can be carried out below 200 ℃

The disadvantages of

AIP are: (1) the existence of coarse droplets in the film increases the surface roughness and the diffuse reflection of light, thus reducing the surface brightness of jewelry; (2) Coarse droplets are easy to peel off during cutting, resulting in defects on the coating surface

There are many kinds of coatings prepared by arc ion plating, involving a wide range of fields, which can be used for the deposition of hard protective coatings. The coatings cover a variety of metal oxides, carbides, nitrides and some metal and alloy materials. It can also be used for the preparation of multilayer structure coatings and nano multilayer structure coatings. It has the characteristics of simple operation of arc ion plating, large space utilization of coating chamber and high production efficiency. In recent years, it has developed into an important technology for depositing hard coatings and has developed rapidly at home and abroad

in recent years, a new coating preparation system adopts composite coating technology, which combines arc ion plating and magnetron sputtering deposition. The system is equipped with several arc and magnetron sputtering cathodes. The arc layer can be used as a transition layer or provide the necessary wear resistance for the whole coating. At the same time, the magnetron sputtering layer provides high temperature and chemical stability. This composite coating technology has the advantages of easy control of deposition process, good stability and repeatability, and its deposition rate (≥ 0.5) μ M/h) is enough to meet the actual requirements for saving treatment time in industrial production

high temperature chemical vapor deposition technology

high temperature chemical vapor deposition (htcvd, generally referred to as CVD) technology refers to that under certain temperature conditions, the mixed gas of coating materials interacts on the surface of cemented carbide to decompose some components in the mixed gas, Gold polyurethane foam is formed on the surface of the cutting tool, which is a kind of high-efficiency thermal insulation material or hard coating of compound

the key to the successful implementation of this method lies in: (1) the interaction between the mixed gas as the coating material and the cemented carbide surface, that is, the mixed gas of the coating material reacts on the cemented carbide surface to produce deposition, or a component of the mixed gas of the coating material reacts with the cemented carbide surface to produce deposition; (2) The deposition reaction must be carried out under certain energy activation conditions

high temperature chemical vapor deposition coating has the following advantages: (1) it is relatively easy to prepare the required coating source; (2) It can deposit single-layer and multi-layer composite coatings such as metal carbide, nitride and oxide; (3) The bonding strength between the coating and the substrate is high; (4) The coating has good wear resistance

it is undeniable that this method has congenital defects. The main points are as follows: (1) the coating temperature is high. That is, the deposition temperature of the coating is higher than 900 ℃, which makes it easy to produce a brittle decarburization layer between the coating and the substrate( η Phase), which leads to the brittle fracture of cemented carbide materials and the decrease of flexural strength; (2) The interior of the coating is in the state of tensile stress, which is easy to cause microcracks when used; (3) The waste gas and liquid discharged in the coating process will cause industrial pollution and have a great impact on the environment. Because of this, the development of this method was restricted in the middle and late 1990s

medium temperature chemical vapor deposition technology

the reaction mechanism of medium temperature chemical vapor deposition (mtcvd) technology is to take organic compounds containing C-N atomic groups such as trimethylammonia and methylimine as the main reaction raw material gas, and decompose and combine with TiCl4, N2, H2 and other gases at 700 ℃ ~ 900 ℃ to produce TiCN and other coatings

The advantages of

mtcvd are: (1) fast deposition speed and low deposition temperature; (2) Thick coating; (3) For complex workpiece with uniform coating; (4) High adhesion of coating; (5) The residual stress in the coating is small. In view of this, this method is easy to industrialize and is better than high temperature chemical vapor deposition coating

mtcvd also has disadvantages: (1) the interior of the coating is in a state of tensile stress, which is easy to cause microcracks when used; (2) The waste gas and liquid discharged in the coating process will cause industrial pollution and be unfriendly to the environment. The above reasons also restrict the development of this technology and method to some extent

the coating with dense fibrous crystalline morphology can be obtained by mtcvd technology, and the coating thickness can reach 8 ~ 10 μ m。 The coating structure has extremely high wear resistance, thermal shock resistance and toughness. It is suitable for use under the conditions of high speed, high temperature, large load and dry cutting. From the perspective of blade life, the service life of the blade can be doubled compared with that of the ordinary coated blade

Plasma enhanced chemical vapor deposition (PECVD) technology refers to the method of generating high-energy electrons through electrode discharge to ionize the gas into plasma, or introducing high-frequency microwave into carbon compound gas to produce high-frequency and high-energy plasma, and depositing coating on the surface of cemented carbide from active carbon atoms or carbon containing groups

advantages of PECVD: (1) it uses plasma to promote chemical reaction and can reduce the coating temperature below 600 ℃; (2) Because the coating temperature is low, there will be no diffusion, phase transformation or exchange reaction between the cemented carbide matrix and the coating material, so the matrix can maintain the original strength and toughness

disadvantages of PECVD: (1) large equipment investment, high cost and high requirements for gas purity; (2) The violent noise, strong light radiation, harmful gas, metal vapor and dust produced in the coating process are harmful to human body; (3) It is difficult to coat the inner surface of the small hole

the treatment temperature of PECVD process has been reduced to 450 ~ 650 ℃, which effectively inhibits η It can be used for tin, TiCN, tic and other coating applications of thread cutters, milling cutters and molds, but so far, this process is not widely used in the field of tool coating

Figure 3 overview of tool coating application in factories of industrialized countries

conclusion

(1) the cutting tool coating technology is still dominated by vapor deposition technology, and sol-gel method and thermal spraying method need further research and development

(2) physical vapor deposition has the advantages of low temperature and less environmental pollution. Therefore, it has developed rapidly in recent years, among which magnetron sputtering deposition and arc ion plating deposition are the most significant

(3) physical vapor deposition and chemical vapor deposition will still coexist and complement each other in the coating of cutting tools, and occupy their respective shares in the coating proportion because of their own advantages. Generally speaking, steel tools such as high-speed steel, sharp cemented carbide precision cutting blades and cemented carbide finishing tools广州产后脱发严重该怎么办
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