PVD (Physical Vapor Deposition Technology)

1. Introduction to PVD
PVD is the abbreviation of the English Physical Vapor Deposition (physical vapor deposition). It refers to the use of low-voltage and high-current arc discharge technology under vacuum conditions, using gas discharge to evaporate the target and ionize the evaporated substance and gas, and use the acceleration of the electric field to deposit the evaporated substance and its reaction products on the workpiece.



2. Development of PVD Technology

PVD technology appeared in the late 1970 s. The prepared films have the advantages of high hardness, low friction coefficient, good wear resistance and chemical stability. At first, the successful application in the field of high-speed steel tools has attracted great attention from manufacturing industries all over the world. While people are developing high-performance and high-reliability coating equipment, they have also carried out more in-depth coating application research in hard alloy and ceramic tools. Compared with CVD process, PVD process has low treatment temperature and has no effect on bending strength of tool materials below 600 ℃. The internal stress state of the film is compressive stress, which is more suitable for coating hard alloy precision and complex tools. PVD process has no adverse effect on the environment and conforms to the development direction of modern green manufacturing. At present, PVD coating technology has been widely used in the coating treatment of hard alloy end mills, drill bits, step drills, oil hole drills, reamers, taps, indexable milling inserts, special-shaped tools, welding tools, etc.

PVD technology not only improves the bonding strength between the thin film and the tool matrix material, but also develops the coating composition from the first generation of TiN to TiC, TiCN, ZrN, CrN, MoS2, TiAlN, TiAlCN, TiN-AlN, CNx, DLC and ta-C and other multi-component composite coatings.

3. Main methods

① The basic principle of vacuum evaporation is to evaporate metals, metal alloys or compounds under vacuum conditions, and then deposit them on the surface of the substrate. The evaporation method is usually resistance heating, high-frequency induction heating, electron beam, laser beam, and ion beam high-energy bombardment The plating material is evaporated into a gas phase, and then deposited on the surface of the substrate. Historically, vacuum evaporation is the earliest technology used in the PVD method.

② The basic principle of sputtering coating is to make argon gas glow discharge under the vacuum condition of argon (Ar) gas. At this time, argon (Ar) atoms are ionized into argon ions (Ar). Under the action of electric field force, argon ions accelerate bombarding the cathode target made of plating material, and the target material will be sputtered out and deposited on the surface of the workpiece. If DC glow discharge is used, it is called DC (Qc) sputtering, and radio frequency (RF) glow discharge is called RF sputtering. Magnetron sputtering caused by magnetron (M) glow discharge.

③ The basic principle of arc plasma coating is to use an arc-starting needle to start an arc under vacuum conditions to cause arc discharge between the vacuum gold wall (anode) and the plating material (cathode), and the cathode surface moves quickly. The cathode arc spot continuously evaporates and even "different China" plating material to ionize it into arc plasma with the plating material as the main component, and can quickly deposit the plating material on the substrate. Because there are multi-arc spots, it is also called multi-arc evaporation ionization process.

④ The basic principle of ion plating is to use a certain plasma ionization technology under vacuum conditions to partially ionize the atoms of the plating material into ions, and at the same time generate many high-energy neutral atoms, and apply a negative bias on the substrate to be plated. In this way, under the action of deep negative bias, ions are deposited on the surface of the substrate to form a thin film.

4. PVD process steps

Physical vapor deposition technology can be divided into three process steps:

① Gasification of plating material: even if the plating material evaporates, sublimates or is sputtered, it passes through the gasification source of the plating material.

② Migration of atoms, molecules or ions in plating materials: atoms, molecules or ions supplied by gasification sources will produce various reactions after collision.

③ The atoms, molecules or ions of the plating material are deposited on the substrate. physical vapor deposition technology has simple process, improved environment, no pollution, less consumables, uniform and compact film formation, and strong binding force with the substrate. This technology is widely used in aerospace, electronics, optics, machinery, construction, light industry, metallurgy, materials and other fields, and can be prepared with wear resistance, corrosion resistance, decoration, conductivity, insulation, light guide, piezoelectric, magnetic, lubrication, Superconductivity and other characteristics of the film.

With the development of high technology and emerging industries, many new and advanced highlights have appeared in physical vapor deposition technology, such as multi-arc ion plating and magnetron sputtering compatible technology, large rectangular long arc targets and sputtering targets, non-balanced magnetron Sputtering target, twin target technology, ribbon foam multi-arc deposition winding coating technology, strip fiber fabric winding coating technology, etc., the complete coating equipment used is fully automatic to the computer, large-scale industrial scale direction.