ВИСОКОЕНТРОПІЙНА КЕРАМІКА ДЛЯ ТЕРМОБАР’ЄРНИХ ПОКРИТТІВ НА ОСНОВІ ZrO₂, КОМПЛЕКСНО ЛЕГОВАНОГО ОКСИДАМИ РЗЕ

Abstract

Current studies of materials for the ceramic layer in next-generation thermal barrier coatings (TBCs) are focused mainly on ternary, quaternary, and more complex oxide systems. The use of high-entropy TBC ZrO₂-based ceramics doped with a mixture of rare-earth metal (REM) oxides was studied and the properties of the TBC ceramic layer deposited by EB-PVD in one process cycle were examined. For research, a REM concentrate based on cerium oxide (light concentrate (LC)) with the following composition (wt.%) was selected: 62.4 CeO₂, 13.5 La₂O₃, 10.9 Nd₂O₃, 3.9 Pr₆O₁₁, 0.92 Sm₂O₃, 1.2 Gd₂O₃, 0.24 Eu₂O₃, 2.66 ZrO₂, 1.2 Al₂O₃, and 1.7SiO₂; the total content of other oxides was 1.38. Targets for spraying the TBP ceramic layer were produced by the ceramic method from a 85 wt.% M-ZrO₂–15 wt.% LC mixture. Two-layer metal/ceramic thermal barrier coatings were deposited employing an UE-174 industrial electron-beam installation, operated at ELTECHMACH (Vinnytsia), onto model blades made by directional crystallization from the ZhS-26VI alloy. A rough dense glossy coating was established to form. The coating on the blade back and entrance edge was 85 μm thick and on the blade pressure side was 70 μm thick. The coating phase composition was a mixture of F-ZrO₂ and M-ZrO₂. Columnar, rather dense crystallites collected in feather-like formations were observed in the ceramic layer. Vertical pores formed between them; they were located perpendicularly or at an angle to the surface. A complex Al₂O₃-based spinel layer 2–2.5 μm thick formed between the ceramic and metal binder layers. The ceramic layer acquired a laminar structure under the synergistic effect of components in the ZrO₂–REM concentrate mechanical mixture in the vapor deposition process. The microstructural features of the coating determined the gradient of microhardness distribution along its height. Thermal cycling experiments showed that this coating withstood 161 thermal cycles, which was higher than that of the standard YSZ coating (138 thermal cycles). Previous studies showed ZrO₂ stabilization with REM oxide concentrates for microstructural design of the TBC ceramic layer.