Metallic contaminations in TBC

[derek]

We spray TBC by SG-100 gun but there were too much metallic contaminations(approximately 2%) in the top coating. Does anyone can hlep me to solve this problem? How to adjust the spray parameters?

Thanks,

[Gordon]

Hi Derek

Welcome to the Surface Engineering Forum.

Metallic contamination of thermal barrier ceramic coatings could be caused by:

1. Contamination in as received powder (unlikely)
2. Contamination from handling, powder feeder hoppers and feed hoses
3. Metal dust being entrained in plasma spray stream
4. Nozzle/electrode erosion
   

Have you identified the metallic inclusions in the coating? If they are tungsten or copper, this will tend to indicate excessive gun nozzle/electrode erosion and you will be suffering very short life from these parts. Time to service and calibrate equipment. If it is from other metals, then chances are, it is a case of poor house keeping. Common one is not cleaning powder feed hopper and hoses when changing from metal to ceramic powder.

[derek]

Thanks a lot Gordon, I do not have any method to identify the matallic inclusions but I try the different powder lot number, it works. The metallic contaminations was in limited.