Brief notes about the deposition technology
Surface treatments can be divided into two main categories:
- filler surface treatments
- surface modification treatments
The “filler surface treatments” are also referred to as “coatings” and among all coatings the best known are galvanic, CVD, PVD and PACVD. Among the “surface modification treatments, to name just the most popular, we find nitriding, cementation and oxidation.
Filler surface treatments
Coatings allow the deposition of compounds with different intrinsic properties.
The deposition mechanisms are common in all the various technologies used and can be summarized in three steps:
CVD technology (Chemical Vapor Deposition), for example, generates metal vapors through a chemical reaction. The transport is accomplished through an atmosphere of gaseous reactants and the deposition occurs by condensation of these vapors on the surface.
Physical Vapor Deposition PVD In the case of PVD, the generation is physical and has place by evaporating the metals which make up the coating. The transport from the sources to the parts to be treated takes place through a vapor or plasma (ionized gas at low pressure). The deposition is rather favored by the presence of an electric field. PVD techniques are many, but can briefly be divided into solid-source techniques(cathodic deposition, such as arc or sputtering) and melted-source techniques (such as evaporation, electron gun or Joule effect).
The growing search for new compounds to be deposited, has pushed the development in the cathode sources direction, in order to become able to deposit alloys of different elements, such as nitrides of titanium and aluminum or titanium nitride and silicon. This development has helped to improve the application characteristics of this technology, while reducing blemishes.
Today for example, with the cathodic arc it is possible to reach high levels of ionization of the plasma, through the use of new generation sources which improve the intrinsic quality of the deposited layers and at the same time they allow to minimize the droplets phenomenon that has always been considered the only disadvantage of this technology.