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Development of vacuum coating technology

1. Vacuum coating technology has not started for a long time. In the 1960s, CVD (Chemical Vapor Deposition) technology was applied to cemented carbide tools. Since the technology needs to be carried out at high temperatures (process temperature is higher than 1000oC), the coating type is single and the limitations are very large, so the initial stage of development is unsatisfactory.

2. At the end of the 1970s, PVD (Physical Vapor Deposition) technology began to emerge, creating a new world of bright prospects for vacuum coating. After a short period of two or three decades, PVD coating technology developed rapidly. The reason is because it forms a film in a vacuum-tight cavity, and there is almost no environmental pollution problem, which is beneficial to environmental protection; because it can get a bright and luxurious surface, in color, it is mature in seven colors, silver, Transparent, gold, black, and any color from gold to black can be described as colorful, to meet the needs of decorative; and due to PVD technology, it is easy to obtain high hardness that is difficult to obtain by other methods. Highly wear-resistant ceramic coatings and composite coatings, applied to tooling and molds, can double the life and achieve low cost and high profitability. In addition, PVD coating technology has low temperature and high energy. Two features can be formed on almost any substrate. Therefore, the application range is very broad, and it is not surprising that it develops rapidly. Vacuum coating technology has developed into new technologies such as PCVD (Physical Chemical Vapor Deposition) and MT-CVD (Medium Temperature Chemical Vapor Deposition), and various coating equipments and various coating processes have emerged in this field. It has presented a gratifying scene of a hundred flowers blossoming and a hundred schools of thought contending.

3. At the same time, we should also clearly see that the development of vacuum coating technology is seriously unbalanced. Due to the extremely harsh working environment of the tool and the mold, the adhesion of the film is much higher than that of the decorative coating. Therefore, although the manufacturers of decorative coatings have spread all over the place, there are not many manufacturers capable of producing mold coatings. Coupled with the lack of after-sales service for tool and mold coating, so far, most domestic coating equipment manufacturers can not provide complete tool coating technology (including pre-treatment process, coating process, post-coating process, inspection). Technology, coated tools and mold application technology, etc., and it also requires process technicians, in addition to professional knowledge of coatings, should also have solid knowledge of metal materials and heat treatment, pre-treatment of mold coating front surface Knowledge, tools, reasonable choice of mold coating and technical requirements for use on the machine, if there is a problem in any link, will give users the conclusion that the use effect is not ideal. All of these have severely restricted the application of this technology to tools and molds.

4. On the other hand, because this technology is an emerging edge discipline in the fields of materials science, physics, electronics, and chemistry, it is one of the few backbones in the field of tool and mold production in China. Manufacturers, most of them are also a way to introduce advanced equipment and technology from abroad, and still need a process of digestion and absorption. Therefore, the current domestic technical strength in this field is not commensurate with its development, and it is urgent to catch up.

5. Physical vapor deposition is divided into: vacuum evaporation coating, vacuum sputtering coating and vacuum ion plating. We usually refer to PVD coating, which refers to vacuum ion plating; generally speaking, NCVM coating refers to vacuum evaporation coating and vacuum sputtering.

6. Basic principle of vacuum evaporation: Under vacuum conditions, metals, metal alloys, etc. are evaporated and then deposited on the surface of the substrate. The evaporation method is usually performed by resistance heating, electron beam bombardment of the plating material, evaporation into a gas phase, and deposition on the substrate. Surface, historically, vacuum evaporation is a technique used in the PVD method.

7. Basic principle of sputter coating: Under the vacuum condition of argon (Ar) gas, argon gas is subjected to glow discharge. At this time, argon (Ar) atoms are ionized into argon ions (Ar), and argon ions are under the action of electric field force. Accelerating the bombardment of a cathode target made of a plating material, which is sputtered out and deposited on the surface of the workpiece. The incident ions in the sputter coating are generally obtained by glow discharge, in the range of l0-2Pa to 10Pa, so that the sputtered particles collide with the gas molecules in the vacuum chamber during the flying to the substrate, so that the direction of motion Randomly, the deposited film is easy to be uniform.

8. The basic principle of ion plating: under vacuum conditions, using a plasma ionization technology, the atomization of the plated part of the ion into ions, while producing a number of high-energy neutral atoms, adding a negative bias on the substrate to be plated. Thus, under the action of a deep negative bias, ions are deposited on the surface of the substrate to form a thin film.

9. Ion plating process: The particles of the evaporating material are injected into the surface of the workpiece at a high speed as a positively charged high-energy ion under the attraction of a high-pressure cathode (ie, a workpiece).

10. The process of ion plating is as follows: the evaporation source is connected to the anode, and the workpiece is connected to the cathode. When the high-voltage direct current is three to five kilovolts, a glow discharge is generated between the evaporation source and the workpiece. Since the vacuum envelope is filled with an inert argon gas, part of the argon gas is ionized under the action of the discharge electric field, thereby forming a plasma dark region around the cathode workpiece. The positively charged argon ions are attracted by the negative high voltage of the cathode, violently bombarding the surface of the workpiece, causing the surface particles and dirt of the workpiece to be thrown and thrown, so that the surface to be plated of the workpiece is sufficiently ion bombarded and cleaned. Subsequently, the evaporation source AC power is turned on, and the evaporated material particles are melted and evaporated, enter the glow discharge region, and are ionized. The positively charged evaporating material ions are rushed toward the workpiece along with the argon ions under the attraction of the cathode. When the evaporating material ions ejected on the surface of the workpiece exceed the number of spattered ions, they gradually build up to form a layer of strong adhesion. Coating on the surface of the workpiece. This is the simple process of ion plating.