Comparison of Al₂O₃ and Al₂O₃-TiO₂ Coatings Manufactured by Aqueous and Alcoholic Suspension Plasma Spraying

Alumina-titania plasma spray coatings are widely used for their tribological performances. The combination of these two ceramics in a particular mix percentage permits to manufacture coatings with better wear resistance in comparison to those made of pure alumina. Suspension plasma spraying permit to manufacture sub-micrometer structure coatings very fine structure thanks to precursors which have an initial size of 10 to 300 nm. The use of a liquid feedstock, aqueous or alcoholic, allows the use of nanometer particles directly without the need to agglomerate them to obtain conventional nanostructured micrometer-sized powders. This study aims at studying Al₂O₃ and Al₂O₃-TiO₂ coatings made from aqueous and alcoholic suspensions produced by suspension plasma spraying. Microstructures and phase evolutions are considered. Manufactured coatings present different architectures depending of operating parameters and feedstock particle sizes; the lower the particle diameter, the thinner the microstructure. Phases composition are discussed and compared to conventional micrometer-sized structure Al₂O₃ and Al₂O₃-TiO₂ coatings.