Microstructure and Deposition Mechanism of Suspension Plasma Spraying Thermal Barrier Coatings

Nanostructured ceramic coatings are a promising research hotspot in the field of thermal protection coatings. Suspension plasma spraying is a practical thermal spaying technique to produce nanostructured thermal barrier coatings. In this paper, nanostructured 8YSZ (8 wt.% yttria-stabilized zirconia) thermal barrier coatings were fabricated using feedstocks of nano-8YSZ suspension by suspension plasma spraying, which was improved from air plasma spraying equipment attached to the atomizer feedstock device. Coatings microstructural analysis and testing were carried out by scanning electron microscope (SEM), and porosity was measured in cross-sectional SEM micrograph. The single scanning deposition status of 8YSZ coatings was investigated, analyzing SEM micrographs of single scanning coatings using different process parameters that included other solvents and additional locations in the plasma jet. The results show that deposition efficiency is higher using alcohol as a solvent, and a better melting state existed in the middle of the plasma jet. The cross-sectional microstructures in different thickness coatings were comparatively researched. More defects were observed in the microstructure of thicker coating, which can be produced by more residual thermal stress. This dramatically improves the thermal cycling performance of the coating.