Plasma Spray
A high frequency arc is ignited between an anode and a tungsten cathode. The gas flowing through between the electrodes is ionized such that a plasma plume several centimeters in length develops. The temperature within the plume can reach as high as 15000¡É. The spray material is injected as a powder outside of the gun nozzle into the plasma plume, where it is melted, and hurled by the gas onto the substrate surface.
- Plasma gas: argon, nitrogen, hydrogen, helium
- Coating material: powder form
Advantage
- Available ceramics coating having high melting point
- Relatively high coating density
- Low oxides in the coating layer using inert gas shielding
Disadvantage
- Expense coating equipment, complex to control coating parameters
- Lower coating density and bond strength than HVOF
Applications
- Metal coating: Ni-base, Co-base, MCrAlY
- Ceramics: Al2O3, Cr2O3, TBC(YSZ, ZrO2)