Chemical composition change behaviors of composite abradable powders during thermal spraying process

Chemical composition differences between the feedstock powder and the final coating of a series of composite abradable coatings were investigated. Graphite filler material mass distributions in the coating, falling powder and burned power is calculated. A preliminary mechanism of graphite loss during the deposition process is established. It is found that graphite content in the coating is significantly lower than that in the feedstock powder. Over 70% graphite in the feedstock powder is lost during the deposition process, and roughly half of the lost graphite is burned and the other half falling. Melting and shrinkage of nickel shell of nickel clad graphite particle as flying through the flame, which resulted in the exposure of graphite core to the flame and substrate, is the main reason for graphite loss and chemical composition change between the feedstock powder and the final coating.