In plasma spraying, the nozzle is the anode: a water-cooled copper part, often tungsten-lined, through which the plasma exits and to which the arc attaches. Arc erosion roughens its bore over time, causing unstable voltage, buildup and spitting, so nozzles and their matching tungsten cathodes are changed on a fixed arc-hour schedule. In HVOF and cold spray guns the nozzle is the converging-diverging section that accelerates the gas.
Nozzle bore is pitted right at the arc root, swap it and the electrode together before the next lot.
Change the nozzle and electrode as a pair and log the hours; mixing a new anode with a worn cathode makes voltage hard to bring back to baseline.
Also heard as
- anode
- anode nozzle
Related terms
Gun
Booth word for the thermal spray torch itself, whether plasma, HVOF, arc or flame.
Gun voltage
The arc voltage of a plasma gun, watched as a live indicator of gas mix, power and hardware wear.
Spitting
A gun shedding blobs of molten buildup into the coating, leaving lumps known as spits.
Plasma spray
Spraying powder through an electric arc plasma jet hot enough to melt ceramics and refractory metals.