INSTITUTE OF TECHNOLOGY OF METALS

DEVEOPMENT OF THE INSTITUTE :: Nontransferred Plasma Arc Spraying

        Nontransferred Plasma Arc Spraying a thermal spray process in which a nontransterred arc is a source of heat that ionizes a gas which melts the coating material and propels it to the workpiece.

        Plasma is present in any electrical discharge even one as in an ordinary arc or in a vacuum tube. It is cold plasma that excites the phosphors within a fluorescent tube.

        Today's plasma spray guns are sufficiently robust to produce temperatures from 5,000°C (9,032°F) to 16,000°C (28,832°F) for long periods. These guns are referred to as "nontransferred arc plasma generators". The generator is essentially an electric arc working in a constricted space. Two electrodes, front (anode) and rear (cathode), are contained in a chamber, as is the arc through which the effluent (the operating gas) passes.

        Typical plasma forming gases include argon, nitrogen, hydrogen and helium. They may be used either alone or in combination: viz, argon-hydrogen, argon-helium, nitrogen-hydrogen, etc.