Nanostructured YSZ thermal barrier coatings obtained by atmospheric plasma spray

The enhancement of turbojets performances in terms of efficiency, thrust and reliability strongly depends on the design of the turbine hi-pressure stages, and in particular by the maximum inlet gas temperature. A lot of studies are focused on the development of materials with improved thermo-mechanical properties in order to increase the working temperatures and to extend the time between inspection and/or substitution of the relevant components. One of the main requirement for ceramic TBC is the resistance to repeated thermal cycles during working life, while assuring the protection of substrate against heat: it is evident that the fragile behaviour of traditional ceramics is a critical issue. One of the possible solutions to the aforementioned problem can be the adoption of nanostructured materials, that at least theoretically provide higher fracture toughness and thermal shock resistance than traditional ones. As thermal spraying is the most efficient and economical deposition technique for thermal barrier coatings, it appears sensible to investigate the possibility of using it for the manufacturing of nanostructured thermal barrier coatings, due to the very short residence time of starting materials at high temperature. A careful selection of process parameters is necessary for preventing the shortcomings correlated to the risk of grain coarsening and phase changing. In the present communication, preliminary results concerning the characterization of zirconia-yttria APS nanostructured coatings (obtained by deposition of commercially available nanostructured powders) as well as a comparison with the performances of conventional microstructured coatings are presented.