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<p>Optimized Al plating layers with controlled thicknesses were applied to the NiCoCrAlY-8YSZ-RSZ thermal barrier coating. The hot corrosion characteristics of the coatings were assessed in a molten sulfate mixture for a duration of 200&#xa0;h at 1100&#xa0;°C. Results demonstrated that the specimen without Al plating gained 19.27 ± 0.53&#xa0;mg&#xa0;cm<sup>–2</sup> in weight, corroded rapidly, and eventually cracked and failed. However, the specimen with Al plating triggered the in situ production of a substantial α-Al<sub>2</sub>O<sub>3</sub> phase during corrosion, restricting O<sub>2</sub> and SO<sub>4</sub><sup>2–</sup> ions from infiltrating the coating. The structural deterioration of the coatings was found to be reliant on the Al plating thickness. The shielding effect of the 5&#xa0;µm Al plating coating was compromised prematurely via the rapidly occurring interaction of <i>α</i>-Al<sub>2</sub>O<sub>3</sub> with SO<sub>4</sub><sup>2–</sup>, leading to its depletion. Driven by excessive thermal mismatch stress from the 15&#xa0;µm Al plating, the coating experienced stress levels beyond its fracture limit, ultimately leading to extensive structural degradation. When the Al plating thickness was optimized to 10&#xa0;µm, the coating displayed a desirable equilibrium between thermal stress and corrosion resistance. This was evidenced by the weight gain of 10.67 ± 0.25&#xa0;mg&#xa0;cm<sup>–2</sup>, approximately 50% less than without Al plating coating, and the highest structural integrity observed during sulfate-induced hot corrosion. This study presents a thickness-modulation strategy for the top Al plating layer, based on the finding that Al plating imparts structural stability to the NiCoCrAlY-8YSZ-RSZ thermal barrier coating. Hot sulfate corrosion tests conducted at 1100&#xa0;°C in an oxidizing environment reveal that variations in Al plating thickness result in distinct degradation behaviors within the dual-ceramic coating. The results demonstrated that optimized Al plating promoted the in situ formation of a dense <i>α</i>-Al<sub>2</sub>O<sub>3</sub> layer on the coating surface and revealed the critical role of Al plating thickness in governing coating degradation, thereby providing guidance for optimizing Al-modified thermal barrier coating systems.</p>

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Hot Corrosion Characteristics of 8YSZ-RSZ Dual-Ceramic Coating with Varied Al Plating Thicknesses at 1100 °C

  • 期刊论文

  • 发表日期：

    2026年6月16日

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  • Liang Gao,
  • Jianing Zhang,
  • Shuaibo Cui,
  • Yongjun Chen,
  • Zhiwen Xie

摘要

Optimized Al plating layers with controlled thicknesses were applied to the NiCoCrAlY-8YSZ-RSZ thermal barrier coating. The hot corrosion characteristics of the coatings were assessed in a molten sulfate mixture for a duration of 200 h at 1100 °C. Results demonstrated that the specimen without Al plating gained 19.27 ± 0.53 mg cm–2 in weight, corroded rapidly, and eventually cracked and failed. However, the specimen with Al plating triggered the in situ production of a substantial α-Al2O3 phase during corrosion, restricting O2 and SO42– ions from infiltrating the coating. The structural deterioration of the coatings was found to be reliant on the Al plating thickness. The shielding effect of the 5 µm Al plating coating was compromised prematurely via the rapidly occurring interaction of α-Al2O3 with SO42–, leading to its depletion. Driven by excessive thermal mismatch stress from the 15 µm Al plating, the coating experienced stress levels beyond its fracture limit, ultimately leading to extensive structural degradation. When the Al plating thickness was optimized to 10 µm, the coating displayed a desirable equilibrium between thermal stress and corrosion resistance. This was evidenced by the weight gain of 10.67 ± 0.25 mg cm–2, approximately 50% less than without Al plating coating, and the highest structural integrity observed during sulfate-induced hot corrosion. This study presents a thickness-modulation strategy for the top Al plating layer, based on the finding that Al plating imparts structural stability to the NiCoCrAlY-8YSZ-RSZ thermal barrier coating. Hot sulfate corrosion tests conducted at 1100 °C in an oxidizing environment reveal that variations in Al plating thickness result in distinct degradation behaviors within the dual-ceramic coating. The results demonstrated that optimized Al plating promoted the in situ formation of a dense α-Al2O3 layer on the coating surface and revealed the critical role of Al plating thickness in governing coating degradation, thereby providing guidance for optimizing Al-modified thermal barrier coating systems.