Analysis of microstructure and thermal shock resistance of nanostructured zirconia thermal barrier coatings

Air plasma spraying was applied to prepare the nanostructured and conventional zirconia thermal barrier coatings. The microstructure and phase composition of the as-sprayed coatings were determined by the FESEM and XRD. The thermal shock resistance of these two coatings have been systematically investigated and compared. The results indicated that the nanostructured TBCs exhibited a unique complex structure consisting of columnar grains and non-molten or partial molten nanosized particles. The predominant phase of the coatings was metastable tetragonal phase. The experimental results of the thermal shock resistance showed that the nanostructured TBCs possessed better thermal shock resistance compared with the conventional coatings. This phenomenon was ascribed to the relatively densified coatings, microcracks, nanosized grains and fine porosity which could effectively release the thermal stress. And the thermal stress was the main reason leading to the failure of the coatings.