Hi Milliaw
to the Surface Engineering Forum.
While having little experience with SG-100 gun, I have seen the problem with other plasma guns. I think the problem is caused by powder fines being caught up in turbulence around powder port and nozzle face area. Very often it is associated with or even caused by powder port fouling. I have seen extreme situations where fouling bridges between powder port and nozzle face.
Possible actions for reducing problem:
* Change powder to one with lower fine content (that "green smoke" you see when pouring the stuff)
* Polish nozzle face and powder port tip to reduce adhesion
* Lower powder feed rate
* Adjust carrier gas flow and or plasma parameters - careful - this will impact on coating quality/deposit efficiency
* Changes to cooling air jet set-up
* Strict regime of periodic nozzle/powder port cleaning