Ceramic build up on end of nozzle

[Milliaw]

What cuases build up of ceramic coating on edge of nozzle and causes spitting on parts?

[LEN WOOD]

While this can be managed by periodic cleaning of the nozzle and powder port/injector some systems are worst than others. If you're parameters are correct and optimal then this is a something that occurs with ceramics, especially under the 'right' conditions. However there are a few tricks to lessen the phenomenon.

What gun and powder are you using?

GB

[Milliaw]

SG-100 and H.C Stark Amperit 831.007

[2DOGSTAR2]

This can be caused by many problems, too much powder too little carrier gas to low current.
I would start by doing a powder feed test, record this and then lower feed rate, watch for any improvement,
Then I would increase carrier gas and see if this improves. If not then increase0current slightly.
I would suggest playing with each parameter one at a time and record all of the results.
It could also be the powder, temperature prior to coatiing or even the batch.
Hope this helps you a little.
Lee
lee@universalthermal.co.uk
http://www.universalthermal.com

[Gordon]

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