Phase Composition Changes of Plasma Sprayed TiO2 Coatings Deposited Under Different in-Flight Temperatures and Velocities

The changes in phase composition of titania (TiO2) coatings were studied with respect to the in-flight characteristics of the powder during atmospheric plasma spraying. Utilizing SprayWatch CCD camera system, average temperature and velocity of TiO2 particles were recorded within the plasma jet under various spraying parameters modified according to Taguchi design of experiment. Six unique combinations of parameters resulting in low/medium/high in-flight temperatures and/or velocities were selected for coating preparation. Phase composition of the produced coatings was assessed using X-ray diffractometry and numerically specified using Rietveld analysis. Relative changes of the composition with respect to the phase composition of the initial heat treated powder feedstock were observed with respect to the measured in-flight characteristics. It was found the in-flight temperature has moderate effect on the phase composition of the produced coatings. For comparison purposes, additional coatings were deposited utilizing cold spray technology. Inferior phase composition changes were observed in cold sprayed samples.