Comparison of microstructures and thermal insulation capability of plasma sprayed nanostructured and traditional YPSZ coatings

Abstract

Microstructural features and thermal insulation capability of plasma sprayed nanostructured and traditional yttria partly stabilised zirconia (YPSZ: ZrO₂–8Y₂O₃) coatings were investigated. Both nanostructured YPSZ coating and traditional YPSZ coating were mainly composed of non-transformable t-ZrO₂ phases. The detailed microstructures of the nanostructured YPSZ coating were observed using FESEM, which presented three types of microstructures: columnar grains, equiaxed grains and nanosized zirconia particles embedded in the so called matrix formed by melted powders. However, the traditional YPSZ coating only contained columnar and equiaxed grains. The average porosities of nanostructured and traditional YPSZ coatings are 12·5 and 9·7 respectively. Compared with the traditional YPSZ coating, the nanostructured coating contained finer microcracks. The nanostructured YPSZ coating has higher thermal insulation capability than the traditional YPSZ coating. For YPSZ coating of 200 μm in thickness, the temperature drop ΔT (thermal insulation capability) of the nanostructured coating at 1350°C increased by 27 compared with that of the traditional coating.