Thermal Plasma Spray Excess Oxides

[Tom Young]

We have been trying to qualify multiple different powders for our plasma spray system. We keep getting failures dues to excess oxides. We have gone through the whole system, new grit, cleaned out blast cabinets etc. but keep getting the excess oxides. First time this has happened with multiple powders and trying multiple times. I believe a total of 10 times combined over the two powders. I hadn't found out that the air chiller they were using for cooling air was not in operation and the samples were being sprayed without the air chiller cooling air and instead chilled with filtered air directly from the air compressor. To me this has been the only change in the process so it was a red flag for me. Does anyone have experience with this process and similar issue? We cannot get the new Air chiller in until late Oct. but are in need of qualified powders. Any help is much appreciated.