Relationships Between Microstructure and Electrical Properties of RF and DC Plasma-Sprayed Titania Coatings

Abstract

Relationships between electrical properties of thermally sprayed titania coatings and their microstructures have been investigated. It is well known that the quality and properties of the plasma-sprayed coatings are strongly dependent on the in-flight particle characteristics, which directly influences the plasma-sprayed coating microstructures. As far as possible, a broad range of microstructures was produced by using various processes of plasma spraying with different powder size ranges and variation of the plasma operating parameters. The two plasma-spraying processes consisted of direct current (DC) and radio frequency (RF) plasma spraying. The major concern of the study was that plasma-sprayed parameters influence also the stoichiometry of the titania coating resulting in a large variation of their electrical properties. It is the reason why coatings with identical stoichiometry were compared. The comparison between RF and DC plasmasprayed titania coatings highlighted that electrical resistivity was directly linked to the quality of the contact between the splats and their density through the titania plasma-sprayed coatings.