The basic process of evaporation coating is: vacuuming the closed bell jar, after reaching a certain degree of vacuum, the evaporation material is heated to a certain temperature by heating by the evaporation source, and the vaporized material is vaporized and deposited on the surface of the workpiece to form a thin film. . When a plurality of independently controlled evaporation sources are disposed in the evaporation chamber to respectively evaporate the elemental materials constituting the alloy, an alloy film requiring a composition ratio is obtained by controlling the temperature and evaporation rate of each evaporation source. When the reaction vapor deposition method is used, a single material such as an elemental metal is evaporated while being filled with a gas such as O2, CH4 or N2, and the two are reacted to form a compound and deposited into a compound film such as Al 2 O 3 , Cr 2 O 3 , SiO. 2 , TiC, SiC, TiN, ZrN, etc.
When a charged particle (generally Ar ion) with a tens of electron volts or more is bombarded with a solid material, a phenomenon in which atoms or molecules on the surface of the material obtain sufficient energy to escape into the gas phase is called sputtering, and the atom to be sputtered. Or a method in which molecules are collected and deposited into a film is called a sputter coating. The number of atoms or molecules sputtered by an incident ion is called the sputtering yield, and the unit is the number of atoms/ion. For most metals, the ion has a threshold energy in the range of 20 to 40 ev. The kinetic energy of the sputtered atoms is generally 1 to 10 ev, which is higher than the thermal evaporation atoms (about 10-1 ev kinetic energy). Bombardment ions are usually obtained by glow discharge. A method of increasing the quality and deposition rate of the sputtered film is to use a magnetron sputtering method. It can be simply understood as a set of permanent magnets on the back of the target, so that a magnetic field is formed on the surface of the target, and part of the magnetic lines of force are parallel to the target surface, so that the electrons emitted from the target surface are directly flying away from the target surface by the electric field force. It is also returned to the target surface by the Lorentz force of the magnetic field, and magnetically collides with the gas molecules to transfer energy to the gas molecules and ionize them. This structure increases the deposition rate of the film, and also reduces the gas content of the film layer and lowers the temperature rise of the substrate. The use of alloy targets or composite targets will achieve the purpose of depositing specific component alloys for sputtering. The deposition of the compound film is conveniently obtained by sputtering a single target and introducing a certain reactive gas into the discharge gas, which is also called reactive sputtering. When sputtering with a Ti target, a certain amount of reaction gas N 2 , CH 4 and O 2 can be added to the working gas to obtain a film of TiN, TiC, TiO 2 compound, and the partial pressure of the reaction gas can control the composition of the compound. , crystal structure and growth mode.
Ion plating is abbreviated as ion plating, which is a process for partially ionizing vaporized substances by gas discharge under vacuum conditions, and depositing and forming a thin film while bombarding the surface of the substrate. Ion plating has the advantages of high deposition rate of vapor deposition and high deposition energy of sputter coating (actually much higher than the energy of sputtered particles), so that it has strong film/base bonding force, good coating properties and Wide range of plating materials. Moley et al. successfully studied hollow cathode ion plating. In 1976, it was put into practical use in Japan, and in 1979, the setting equipment was put on the market and developed. China's research is lagging behind for several years. In the 1990s, China's imitation hot wire electric ion plating equipment was successfully used for the plating of TiN hardness film on high speed steel tools.
In recent years, foreign PVD equipment has entered the domestic market in large quantities, occupying the market, and some corresponding equipment manufacturers have also established coating processing in China. Some domestic tool factories such as Shanghai Tool Factory, Ha Yigong and some mold factories (Shanghai, such as Shanghai Mint) purchase their own imported equipment for the production of coating tools and molds.
Chemical vapor deposition is a process for depositing a solid film on the surface of a substrate by chemical reaction of a gas phase substance. These chemical reactions include 11 kinds of decomposition, compounding, reduction, and displacement reactions, and the reaction excess (gas) is discharged from the reaction chamber. .
The reactants provided in the CVD may be gaseous, liquid or solid materials at room temperature, and they are vaporized by heating and introduced into the reaction chamber. The reaction chamber also needs to supply energy to the gas or the substrate, and the substrate is generally heated by electric resistance. , high frequency induction heating and infrared heating methods. Thus, the main equipment of CVD includes a reaction gas generation, purification, mixing and introduction device, a reaction chamber and a substrate heating device and an exhaust device.
The chemical reaction temperature of CVD is generally 800-1000 ° C. Due to the high deposition temperature, the selection of the matrix material is limited. The mechanical properties of the substrate are greatly reduced, and the microstructure of the film and film/base is also given. And performance has an adverse effect. In order to lower the deposition temperature, there is a new development in the selection of new reactants and the provision of activation energy to the reaction. Among them, plasma-assisted chemical vapor deposition (PECVD) is more and more important. The plasma can be used to heat the substrate, and the discharge of the reaction gas is activated into very active excited molecules, atoms, ions or clusters thereof, which reduces the activation energy of the reaction and makes the thermodynamically difficult chemical reaction easy to realize. Therefore, the temperature of the chemical vapor deposition is greatly reduced, and the practical use is greatly improved. Many foreign equipments work in the form of PVD and PECVD.
Composite heat treatment is a very active technical field, and some people in the world studied in the 70s and 80s of the last century. Now there are mainly composite treatments of surface heat treatment and chemical heat treatment, surface heat treatment combined with surface deformation strengthening (shot peening), surface plating and surface heat treatment. After compounding, the material achieves unique properties with both treatments. Domestic scholars use shot peening to nano-scale the surface of the part and then nitriding, which can reduce the nitriding temperature to about 350 ° C, and obtain good performance. This work has been greatly valued by foreign counterparts, which is also a compound treatment. A special example.
4. Suggestions and conclusions:
4.1 Heat treatment process is one of the most important basic processes widely used in any industrial field involving mechanical manufacturing. The development of heat treatment processes, techniques and heat treatment equipment should be given full attention.
4.2 The domestic heat treatment equipment and technical level lag far behind the international advanced level.
4.3 The strategic goal of the development of advanced heat treatment technology is sustainable development, improved product quality, energy conservation, precise production and improved production efficiency.
4.4 In the main signs of foreign advanced heat treatment technology, we must pay special attention to: clean production and zero pollution, precise production and zero distortion, less oxidation and less decarbonization, and the development of energy-saving equipment and processes.
4.5 In terms of protective atmosphere and controlled atmosphere heat treatment, foreign advanced technology is embodied in direct-type carburizing technology, vacuum acetylene carburizing technology, controllable high CO gas carburizing technology and stainless steel solid solution nitriding, etc. The control feature is a very important key to ensure that the equipment has high technical characteristics.
4.6 Induction heating treatment, gear simultaneous dual-frequency induction heating technology and liquid medium induction carburizing are two developments of advanced technology. Foreign induction heating quenching equipment is the key to solving high efficiency, automation, process requirements and process quality reproducibility.
4.7 The main key to the technical and processing quality of vacuum heat treatment is equipment. Intelligent control is very important. It should pay attention to high-pressure gas quenching, and change the cooling mode and cooling speed to ensure the production efficiency, reduce deformation and high quality.
4.8 Foreign laser heat treatment equipment is advanced, but investment and application are limited to a certain extent.
4.9 PVD, CVD technology and equipment are developing rapidly, and there are quite a lot of foreign investment in China, and the market prospects are fierce.
4.10 The development and investment of heat treatment technology should focus on high efficiency, low energy consumption, high starting point, high level, low pollution and high quality. With high technology and strict management, we will compete for high-end market and strive for high income and high return.
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