|
The process involves injection of a powder
into a plasma jet stream where it is melted and propelled
onward.
The plasma stream is created in the torch nozzle by heating
an inert gas with an electric arc between water-cooled electrodes.
The efficient melting of the powder grains
due to the high temperature existing in the plasma (up to
20 000 °C) allow the use of high melting point materials
(ceramics, refractory metals...)
High velocity of plasma spraying (about
200 m/s) with the extremely short flight times of the molten
powder particles provide such desirable properties as high
bond strength, high coating density and minimum oxidation.
Spraying parameters are numerous and key factors that determine
the quality of a plasma sprayed coating. |
