Plasma spraying systems can be categorized by several criteria.
Plasma jet generation:
*direct current (DC plasma), where the energy is transferred to the plasma jet by a direct current, high-power electric arc
*induction plasma or RF plasma, where the energy is transferred by induction from a coil around the plasma jet, through which a radio-frequency current passes. This electrode-free technology allows to produce coatings with high purity and high density.
Plasma-forming medium:
*gas-stabilized plasma (GSP), where the plasma forms from a gas; typically argon, hydrogen, helium or their mixtures
*water-stabilized plasma (WSP), where plasma forms from water (through evaporation, dissociation and ionization) or other suitable liquid
*hybrid plasma – with combined gas and liquid stabilization, typically argon and water
Spraying environment:
*atmospheric plasma spraying (APS), performed in ambient air
*controlled atmosphere plasma spraying (CAPS), usually performed in a closed chamber, either filled with inert gas or evacuated
*variations of CAPS: high-pressure plasma spraying (HPPS), low-pressure plasma spraying (LPPS), the extreme case of which is vacuum plasma spraying (VPS, see below)
*underwater plasma spraying
Another variation consists of having a liquid feedstock instead of a solid powder for melting, this technique is known as Solution precursor plasma spray