Process in which a DC arc between a tungsten cathode and a copper anode nozzle ionizes argon or nitrogen mixed with hydrogen or helium, forming a plasma jet whose core exceeds 10,000 K. Powder injected into the jet melts and travels at roughly 100 to 300 m/s to the part. Run in open air it is called APS (air plasma spray), and it is the standard route for zirconia thermal barriers, alumina, chrome oxide and many metallic coatings.
Plasma spray the zirconia top at 600 amps and 4 inches, and keep the cooling air on the back side.
Log voltage, current and gas flows at every light off; most plasma problems show up in those numbers before they show up in the coating.
Also heard as
- APS
- air plasma spray
- atmospheric plasma spray
- plasma
Related terms
Plasma gas
The gas mix ionized in a plasma gun: a primary gas for flow plus a secondary gas for heat.
Nozzle
In a plasma gun, the water-cooled copper anode the arc attaches to; in HVOF, the passage that shapes the jet.
Gun voltage
The arc voltage of a plasma gun, watched as a live indicator of gas mix, power and hardware wear.
VPS
Vacuum plasma spray: plasma spraying inside a low-pressure inert chamber to make oxide-free metal coatings.
Thermal barrier coating
A ceramic coating system that insulates hot-section metal parts from combustion gas temperatures.