There is a large number of competing processes for coating surfaces, and only a few of them will be presented in the next sections, which are the most relevant to the application of overlay coatings (MCrAlY) or TBC.

Coating processes can be broadly divided in methods by which atoms attach individually to the surface, or methods which apply particles. Physical vapour deposition (PVD) or chemical vapour deposition (CVD) are examples of the former. Thermal spraying methods fall in the second category.

An example of CVD has been described earlier (aluminides coatings by pack cementation)

The following sections give a very brief overview of the following processes:

• Thermal spraying: air plasma spray (APS), low pressure plasma spray (LPPS), high velocity oxyfuel spray (HVOF) etc.
• Electron-beam PVD (EBPDV).