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<p>Ammonia, an energy carrier, is a promising alternative carbon-free fuel to hydrogen for power generation. Despite having many beneficial characteristics, the use of ammonia as a direct fuel in gas turbines is restricted due to its corrosive nature. Here, we aim to investigate the behavior of plasma-sprayed ZrO<sub>2</sub>-8&#xa0;wt.% Y<sub>2</sub>O<sub>3</sub> (YSZ)/CoNiCrAlY coating in ammonia containing atmosphere at elevated temperatures. YSZ coating with CoNiCrAlY bondcoat (with and without heat treatment) on Hastelloy X was exposed to 10% ammonia environment at 500 to 900&#xa0;°C for 4&#xa0;h. The post-exposure test characterization revealed no phase alteration, surface morphology variation, and microstructural changes of the YSZ coating itself. A lower weight gain of the YSZ coated specimens with heat-treated (HT) bondcoat as compared to that of the non-heat-treated (NHT) ones was observed. Up to 700&#xa0;°C, no nitridation of the HT bondcoat was detected, whereas nitrided regions consisting of Cr-based and Al-based nitrides were identified at discrete locations in the CoNiCrAlY coating near the topcoat–bondcoat interface above 700&#xa0;°C. On the other hand, significant nitridation of the NHT bondcoat was observed at all the test temperatures. The effect of inherent porosities and inter-splat boundaries on the nitrogen diffusion and consequent nitridation were elucidated.</p>

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Behavior of Thermally Sprayed YSZ/CoNiCrAlY Coating System after Short-term Exposure to High-temperature Ammonia Flow Environment

  • 期刊论文

  • 发表日期：

    2025年12月9日

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  • Tina Ghara,
  • Seiji Kuroda,
  • Takashi Yanagisawa,
  • Mohammed Shahien,
  • Masato Suzuki,
  • Takahiro Inoue,
  • Kentaro Shinoda

摘要

Ammonia, an energy carrier, is a promising alternative carbon-free fuel to hydrogen for power generation. Despite having many beneficial characteristics, the use of ammonia as a direct fuel in gas turbines is restricted due to its corrosive nature. Here, we aim to investigate the behavior of plasma-sprayed ZrO2-8 wt.% Y2O3 (YSZ)/CoNiCrAlY coating in ammonia containing atmosphere at elevated temperatures. YSZ coating with CoNiCrAlY bondcoat (with and without heat treatment) on Hastelloy X was exposed to 10% ammonia environment at 500 to 900 °C for 4 h. The post-exposure test characterization revealed no phase alteration, surface morphology variation, and microstructural changes of the YSZ coating itself. A lower weight gain of the YSZ coated specimens with heat-treated (HT) bondcoat as compared to that of the non-heat-treated (NHT) ones was observed. Up to 700 °C, no nitridation of the HT bondcoat was detected, whereas nitrided regions consisting of Cr-based and Al-based nitrides were identified at discrete locations in the CoNiCrAlY coating near the topcoat–bondcoat interface above 700 °C. On the other hand, significant nitridation of the NHT bondcoat was observed at all the test temperatures. The effect of inherent porosities and inter-splat boundaries on the nitrogen diffusion and consequent nitridation were elucidated.