It is a vaporization coating technique that transfers the material to the atomic level. You might have heard about the electroplating, and it is an alternative to it.
It produces coatings of pure metals, metallic toys, and ceramics with a thickness in the range of 1 to 10 micrometers. The main types of PVD, all of which are undertaken in the chamber containing a controlled atmosphere at reduced pressure, are thermal evaporation, sputtering, and ion plating.
Thermal evaporation used the heating of the material to form a vapor which condenses on the substrate to form the coating. Heating is achieved using the methods, including the hot filament, electrical resistance, laser beam, and the electric arc.
Sputtering involves the electrical generation of plasma between the coating material and the substrate.
Ion plating is a combination of thermal evaporation and sputtering.
This technique can be used for the direct deposition of the material or the ‘reactive use.’ In the latter, the chemical reaction takes place in the vapor phase between the atoms of the coating material and the ‘reactive gases.’
Physical Vapor Deposition (PVD) Process
It is carried out under the vacuum conditions and has four steps:
Evaporation. In this stage, the target, the material to be deposited, is bombarded using a high energy source like electrons- beam or the ions. It removes the atoms from the surface of the target or vaporizes them.
Transport. It consists of the movement of the ‘vaporized’ atoms from the target to the substrate to be coated.
Reaction. The coatings may also consist of metal oxides, nitrides, carbides, and other such materials. The target, in this case, is usually the metal. The atoms of the metal will react with the appropriate gases during the transportation stage. These gases may be oxygen, nitrogen, and methane.
Deposition. It is the process of coating the substrate surface. Depending on it, reactions between the target materials and the reactive gases may take place at the surface along with the deposition.
Uses of PVD Coatings
These coatings are deposited for numerous reasons. It can improve the hardness and wear resistance, reduces friction, and also improves the oxidation resistance. The use of the coatings is aimed at improving efficiency with the help of the improved performance and longer component life. It also allows the coated components to work well in the environment where the uncoated component would not be able to perform or may fail.
Is the Process Environmental Friendly?
The PVD process is very environmentally friendly, or the plating technique reduces the amount of the toxic substances used, managed, and disposed of. In the ‘wet’ processes, there are fluid precursors and chemical reactions that can be used to get the same result. PVD coating can produce extremely pure, clean, and durable coatings. It’s the primary reason why PVD coating is the technology of choice for the surgical and the medical implant industry.
The materials can be deposited with the improved properties as compared to the substrate material. Any type of inorganic material can be used along with some organic variants. The process is environmentally friendly than electroplating.
It can be a challenge to coat the undercuts and similar surface features. The capital costs are usually high, and some processes operate at high vacuums and temperatures that require skilled operators. A large amount of heat requires the appropriate cooling systems. The rate of coating deposition is usually slow.
Physical Vapor Deposition (PVD) coatings are used to improve the hardness, wear resistance, and oxidation resistance. It can be used in aerospace, automotive, surgical/medical, dies and molds, cutting tools, and firearms.