Tribological properties of plasma sprayed alumina–titania coatings: role and control of the microstructure

Plasma sprayed ceramic coatings (Al2O3+40% TiO2) were studied using two different kinds of powder: one spray dried and one crushed and blended. The cooling rate during the thermal spray process was also considered, with the use of cryogenic cooling. The friction behavior and the wear resistance of the corresponding coatings were then evaluated in dry sliding conditions in two different configurations: block-on-ring (Amsler) and ball-on-disc. The microstructure of a coating is conditioned by the morphology of the powder and the cooling rate which modify the residual stresses in the coating.