Yttria-stabilised zirconia (YSZ) coatings were deposited on austenitic stainless steel coupons from nanostructured powders using atmospheric plasma spraying (APS). Two suspensions of YSZ nanoparticles were used as starting material: a diluted commercial suspension and a highly concentrated in-house prepared suspension (obtained by adding an YSZ submicronic powder to the diluted suspension). Both suspensions were reconstituted into sprayable micrometric granules. The reconstitution process was performed by spray drying, followed by a thermal treatment in order to reduce porosity and enhance agglomerate sinterability. The reconstituted powders were characterised by XRD, SEM, granule and pore sizing techniques, and a flowability evaluation. The effect of suspension characteristics on granule morphology and porosity was examined. The reconstituted powders were successfully deposited, yielding well-bonded coatings. The coating microstructure was characterised by XRD and SEM. Mechanical properties and erosion resistance were also determined. Coating microstructure consisted of semi-molten feedstock agglomerates surrounded by fully molten areas that acted as binders. The influence of feed powder characteristics on coating microstructure and properties was also studied.

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 Al 2 O 3 and Al 2 O 3 -TiO 2 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 Al 2 O 3 and Al 2 O 3 -TiO 2 coatings.