Method for thermal spray coating and rare earth oxide powder used therefor
The invention discloses an efficient method for the formation of a highly corrosion- or etching-resistant thermal spray coating layer of a rare earth oxide or rare earth-based composite oxide by a process of plasma thermal spray method by using a unique thermal spray powder consisting of granules of the oxide. The thermal spray granules are characterized by a specified average particle diameter of 5 to 80 µm with a specified dispersion index of 0.1 to 0.7 and a specified BET specific surface area of 1 to 5 m 2 /g as well as a very low content of impurity iron not exceeding 5 ppm by weight as oxide. The flame spat powder used here is characterized by several other granulometric parameters including globular particle configuration, particle diameter D 90 , bulk density and cumulative pore volume.