APS 8YSZ/NiCrAlY 热障涂层的制备与高温水氧腐蚀行为研究

With the implementation of the "National Dual-carbon Strategy", gas turbines using pure hydrogen or hydrogen-blended fuels have attracted increasing attention. Consequently, the high-temperature water-oxygen corrosion behavior of thermal barrier coatings on hot-end components has become increasingly serious. However, in recent years, there are still few reports on influences of the presence or absence of water vapor on the micro-structural evolution and oxidation kinetics behavior of YSZ thermal barrier coatings at high temperature. In order to clarify the difference in the oxidation behavior of 8YSZ thermal barrier coatings under high-temperature water-oxygen corrosion and atmospheric conditions, and to provide a preliminary basis for the research on the water-oxygen corrosion resistance of high-performance thermal barrier coatings, 8YSZ/NiCrAlY thermal barrier coatings were prepared by atmospheric plasma spraying. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were used to characterize the microstructure and oxidation kinetics of the coatings after high-temperature heat treatment under water-oxygen corrosion and air atmosphere, respectively. The results showed that the ceramic layer was mainly composed of t'-ZrO₂ and a small amount of m-ZrO₂ after water-oxygen corrosion and oxidation. Compared with the as-prepared coating, there was an obvious powdering phenomenon on the surface of the 8YSZ coating after water-oxygen corrosion, and the degree of powdering increased with the increase of corrosion time. A TGO layer could be observed in the cross-sectional morphology after water-oxygen corrosion for 50 h. A black-contrast layer and a gray-contrast layer could be observed in the TGO layer. At this time, the black-contrast layer was thick and continuous, but as the corrosion time increased, the black-contrast layer became thin and discontinuous. There was no obvious change on the surface of the oxidized 8YSZ coating compared with the as-prepared coating. When oxidized in the atmosphere for 50 h, the black-contrast layer in the TGO layer was already very thin and discontinuous. As the oxidation time increased to 100 h, the black-contrast layer could hardly be observed. Analysis and summary of the above phenomena lead to the following conclusions: In a high-temperature water-oxygen environment, water vapor reacts with the surface 8YSZ to form easily decomposable hydroxides such as Zr(OH)₄ and Y(OH)₃, which destroys the coating surface and causes powdering. The black-contrast layer in the TGO layer is mainly composed of Al₂O₃, and the gray-contrast layer is mainly composed of oxides such as Cr₂O₃, NiO, or Ni(Cr,Al)₂O₄. In the early stage of water-oxygen corrosion, the presence of water vapor might promote the formation of Al₂O₃, making the growth rate of the TGO layer faster. This is manifested by an obvious contrast distribution in the TGO layer, and the thickness of the TGO layer is larger than that after oxidation in the atmosphere for the same time. As the water-oxygen corrosion time increases, water vapor would cause the TGO layer to become porous, resulting in the volatilization of Al₂O₃ and local weight loss. The weight-gain curve of water-oxygen corrosion is lower than that of oxidation. Therefore, it will be urgent to develop coatings resistant to high-temperature water-oxygen corrosion.