Microstructural and Mechanical Characterization of Mechanically-Activated Plasma-Sprayed Nanostructured Al2O3-TiO2 and Al2O3-ZrO2 Coatings
Granulated nanostructured alumina/titania and alumina/zirconia powders were used to achieve coatings by atmospheric plasma spraying. Raw materials and mechanically activated ceramic mixtures (alumina with 13wt% and 44wt% of titania or 40wt% and 80wt% of zirconia) have been considered to produce the sprayable powders. Effects of various plasma spray conditions (primary Ar and secondary H2 gas flow rates, arc intensity) on the microstructure, phase content and microhardness of the coatings have been evaluated. It has been shown by SEM observations that the coatings exhibit a lamellar structure consisting in fully melted and partially melted areas including porosity, ranging from 10 to 30vol.%. The phase changes (from αAl2O3 to γAl2O3, from anatase to rutile for TiO2, Al2TiO5) or structural changes that occur during the plasma spraying of the nanostructured powders were investigated by XRD and related to the processing conditions and in turn to the amount of unmelted powder.
S. Coste et al., "Microstructural and Mechanical Characterization of Mechanically-Activated Plasma-Sprayed Nanostructured Al2O3-TiO2 and Al2O3-ZrO2 Coatings ", Advances in Science and Technology, Vol. 45, pp. 1224-1229, 2006