Sub-Micrometer-Sized Y-PSZ Thermal Barrier Coatings Manufactured by Suspension Plasma Spraying: Process, Structure and Some Functional Properties

Suspension Plasma Spray (SPS) permits to manufacture thick (from 50 to 120 µm) coatings structured at the sub-micrometer or even nano-meter scales. Due to the large volume fraction of the internal interfaces, nanostructured coatings exhibit better properties than conventional microstructured coatings. For example, considering oxide ceramics, they exhibit higher coefficients of thermal expansion (CTE), lower thermal diffusivity and hysteresis (due to phonon scattering by boundary defects), higher hardness and toughness (due to small grain sizes), better wear resistance (due to higher hardness and grain sliding plasticity) This work aimed at manufacturing by SPS yttria-partially stabilized zirconia thermal barrier coatings using two different sub-micrometer-sized commercial powders. By varying operating parameters, several layer architectures and density were achieved. Correlation between operating conditions, thermal and mechanical properties have been addressed, especially the porosity network architecture and the apparent thermal diffusivity. Coatings have been submitted in parallel to a series of thermal and isothermal shocks in order to assess their thermomechanical behaviour.