Microstructure and thermal cycling behavior of nanostructured yttria partially stabilized zirconia (YSZ) thermal barrier coatings

Nanostructured yttria partially stabilized zirconia (YSZ) coatings were prepared by atmospheric plasma spraying (APS) using the conglomeration made by zirconia nanoparticle as the raw materials. The measurement methods, which consisted of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal cycling behavior, were used to character the morphology, composition and thermal oxidation behavior of the powder and the coatings. From the results, it was shown that the YSZ coating was the laminar structure, and the elements distribution in the bond and top coat were well-proportioned. The YSZ coatings were composed of fine grains with size ranging from 30 to 110 nm. The laminar layers with columnar grains were surrounded with unmelted parts of the nanostructured powder and some equiaxed grains. In the as-sprayed nanostructured zirconia coatings, there existed pores that were less than 1 μm. The cracks were observed on some of the crystal border. The cyclic oxidation experiment showed that the nanostructured coating had longer thermal cycling lifetime to exhibit the promising thermal cyclic oxidation resistance. The failure of the nanostructured TBC was similar to the failure of conventional APS TBC.