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 market demand in recent decades. The use of coating technology can effectively extend the service life of the cutting tool and endow the tool with excellent comprehensive mechanical properties, thereby greatly improving the machining efficiency. It is precisely because of this that coating technology, cutting materials and cutting processing technology are collectively referred to as 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 a mechanical cutting tool. In order to meet the requirements of modern machining for high efficiency, high precision, and high reliability, the manufacturing industry in the world pays more and more attention to the development of coating technology and its application in tool manufacturing. Layers of tools account for nearly 60% of the total.
At present, the coating technology methods mainly include vapor deposition method, sol-gel method, thermal spraying method and so on. Among them, the vapor deposition method is widely used, and the quality of the prepared coating is relatively high. Vapor deposition technology can generally be divided into physical vapor deposition (PVD) and chemical vapor deposition (chemical vapor deposition, CVD).
The methods for preparing the surface coating of cutting tools by vapor deposition method 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, plasma enhanced chemical Vapor deposition coating. The most commonly used of these are high temperature chemical vapor deposition, magnetron sputtering deposition and arc ion plating. The following will combine the different mechanisms of various coating technologies to illustrate their advantages and disadvantages. Magnetron sputtering deposition technology Magnetron sputtering coating (magnetron sputtering) technology belongs to the category of glow discharge, using the principle of cathode sputtering for coating. The film particles originate from the cathode sputtering effect of argon ions on the cathode target material in the glow discharge. After the argon ions sputter down the target atoms, they are 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 surface of the target, extending their trajectory in the plasma, thereby increasing their participation in the collision and ionization process of gas molecules.
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, due to magnetron sputtering deposition The coating is the atomic particles obtained by the cathode sputtering method, which carries the higher energy obtained from the target surface to the workpiece, which is conducive to the formation of a small core and a very fine film structure; (4) Magnetron sputtering deposition coating The layer can obtain a large-area thin film, which can be widely used.
However, this method also has the following problems: (1) The target material is not uniformly etched. Due to the uneven distribution of the magnetic field intensity, the utilization rate of the target material is low. This can promote the change of the magnetic field intensity of the target surface by rationally designing the target structure and adding an electromagnetic field to realize discharge scanning, thereby effectively improving the utilization rate of the target. (2) Low metal ionization rate. In response to this, the volume of the magnet in the center of the target can be increased (or reduced) as required, causing part of the magnetic field lines to diverge to near the substrate farther from the target, achieving unbalanced magnetron sputtering (unbalanced magnetron sputtering). It is worth mentioning that the magnetron sputtering method can also be used to prepare multi-layer films and nano-films. With the rapid development of high-tech and emerging processing industries, there is an increasing demand for the deposition of multi-layer films and nano-films with higher performance. increase. Therefore, the magnetron sputtering technology is worthy of further in-depth research and development, and its application prospects are superior.
Tool coating technology
2021 12/27