Superior toughness of thermal barrier coating caused by co-doping of trivalent and pentavalent oxides

Abstract

The zirconia-based thermal barrier coating co-doped with trivalent and pentavalent oxides was deposited on DD 90 single crystal superalloy using air plasma spraying. The coating is composed of cubic and tetragonal phases denoted by bi-phase solid solution (BPS) ceramic coating. The microstructure, cross-sectional morphology, and cracks evolution of BPS coatings, before and after 1200 °C thermal cycling, were investigated compared with 8YSZ coating. The BPS coating is intact after 250 thermal cycles, and the phase constitution is consistent with as-sprayed state. On the contrary, the brittle monoclinic phase can be observed in the thermal cycled 8YSZ coating, and severe exfoliation occurred. The propagation and splitting of the cracks are inhibited by the randomly distributed nanocrystalline clusters, and the cracks are inclined to grow longitudinally, which are beneficial to improve the toughness and thermal shock resistance of thermal barrier coating.