Composite high-entropy (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Ce2O7 thermal barrier coatings with enhanced thermal cycling performance

Abstract

The emerging high-entropy (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Ce2O7 (LECO) has been verified as a potential thermal barrier material. To ensure accurate thermal cycling life prediction of LECO-based coating, double ceramic layered coatings LECO-8YSZ (8YSZ: 8 mol% yttrium stabilized zirconia) (Y-LECO) and composite (25 wt% 8YSZ + 75 wt% LECO)-8YSZ (Y-YLECO) were prepared via atmospheric plasma spraying (APS). In Y-YLECO, the toughening of 8YSZ in LECO effectively impeded the driving force of crack propagation and slowed down the delamination rate of the coating. Thus, the thermal cycling life of Y-YLECO is about 30 % higher than that of Y-LECO. Besides, both coatings exhibited mild delamination behavior. The exfoliation only appeared at the LECO-based coating with tiny flake-like delamination occurring on the surface. Such spallation pattern contributed to alleviating the stress concentration and preventing the further propagation of vertical cracks towards substrate. Moreover, the addition of 8YSZ did not sacrifice the thermal insulation performance of the composite coating, while it was 0.75 W·m−1·K−1 at 1000 °C for 25 wt% 8YSZ + 75 wt% LECO coating, close to the single-component LECO coating (0.67 W·m−1·K−1). The component design strategy could be a new pathway to further enhance the thermal protection performance of the high-entropy coatings.