Effect of CeO2 Doping on the High-Temperature Oxidation of CoAlNiCrFeHfY High-Entropy Coatings

Authors:
  • KLKangcheng Liu
    Kangcheng Liu
  • ZJZhenguo Jiang
    Zhenguo Jiang
  • SXShengquan Xia
    Shengquan Xia
  • YLYi Liu
    Yi Liu
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Abstract
CoAlNiCrFeHfY high entropy coatings containing 0, 0.5, 1, 2, and 3wt.% CeO2 were fabricated, and their oxidation at 1100℃ was systematically investigated. During coating deposition, CeO2 reacted in situ with Al in the molten pool to form Ce-Al-O compounds, which consumed Al and consequently led to the formation of minor Al-depleted phase. Long-term oxidation tests showed that α-Al2O3 was the predominant oxidation product in five coatings. The addition of a small amount of CeO2 (0.5wt.%) reduced the TGO growth rate to some extent and improved its spallation resistance, which was attributed to the REE induced by an appropriate amount of Ce4+ or Ce3+. In contrast, excessive CeO2 addition promoted the precipitation of Ce-rich oxides within the TGO. These precipitates not only increased the ionic diffusion rate by more than threefold, thereby accelerating TGO growth, but also generated high local compressive stresses (~30-40MPa), promoting rapid TGO spallation. These findings provide useful guidance for optimizing the composition of CoAlNiCrFeHfY high-entropy coatings to enhance their oxidation resistance in high-temperature applications.

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