Dense Yttria Coatings Deposited with Axial Plasma Spraying Using Fine Powders

Plasma treatment is used for micro/nano fabrication especially in dry etching, and an increasing plasma power is used to fabricate the large substrates with high etching rate. This trend presents higher requirements on the plasma erosion resistant coatings on the inside wall of the chamber. Traditionally these coatings have been sprayed with air plasma spraying (APS) using Y2O3 powders with typical particle size in the range of 10-60 µm. In recent years, suspension plasma spraying (SPS) was introduced into the manufacturing of dense Y2O3 coatings, which possess better properties for erosion resistance and retention of smoother surface against plasma erosion than that of traditionally APS coatings. In SPS process a liquid feedstock is used, which increases the process complex, thus presenting more challenges for industrial applications. In this paper, dense Y2O3 coatings were sprayed directly using fine powders with particle size in the range 5-20 µm. The coating microstructures and properties (hardness, bond strength, and corrosion resistance) will be presented and compared with that of APS and SPS coatings. Examples of application on parts will also be demonstrated.