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<p>The next generation Advanced Ultra Super Critical (AUSC) thermal power plants, projected to operate at steam temperatures ranging from 710-720&#xa0;ºC and pressures exceeding 30&#xa0;MPa, require materials with superior fireside corrosion resistance under aggressive coal ash and flue gas environments. The current investigation focuses on the fireside corrosion behavior of Alloy 617M, a nickel-based superalloy variant specially modified for the Indian AUSC program and a candidate superheater material. A laboratory-scale fireside corrosion setup using Indian coal ash and capable of simulating flue gas conditions at 750&#xa0;°C is devised for corrosion evaluation up to 2000&#xa0;h of exposure. The detailed surface characterization indicates that Ni-based superalloy 617M forms a protective Cr<sub>2</sub>O<sub>3</sub> film during the initial 1000&#xa0;hours, with minimal metal loss. Prolonged exposure fluxes away Cr from Cr<sub>2</sub>O<sub>3</sub> at the grain boundaries due to the action of low melting alkali metal trisulfate and the localized grain boundary dissolution lead to scale thickening, predominated with Ti diffusion and alumina precipitation enriched along the grain boundaries. Further oxidation showed TiO<sub>2</sub> nodule coarsening via Ostwald ripening, creating Cr<sub>2−x</sub>Ti<sub>2</sub>O<sub>3</sub> outward scale, and increased alumina internal oxidation forming an inhomogeneous internal layer, accompanied by voids and intergranular attack. The study proposes fireside Alloy 617M’s corrosion mechanism for assessing long-term durability in AUSC conditions for the first time.</p>

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Investigation of Fireside Corrosion of Nickel-Based Superalloy 617M for Advanced Ultra Super Critical Coal Fired Boiler Plants

  • 期刊论文

  • 发表日期：

    2026年4月13日

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  • C. Anushree,
  • E. Vetrivendan,
  • S. Ningshen

摘要

The next generation Advanced Ultra Super Critical (AUSC) thermal power plants, projected to operate at steam temperatures ranging from 710-720 ºC and pressures exceeding 30 MPa, require materials with superior fireside corrosion resistance under aggressive coal ash and flue gas environments. The current investigation focuses on the fireside corrosion behavior of Alloy 617M, a nickel-based superalloy variant specially modified for the Indian AUSC program and a candidate superheater material. A laboratory-scale fireside corrosion setup using Indian coal ash and capable of simulating flue gas conditions at 750 °C is devised for corrosion evaluation up to 2000 h of exposure. The detailed surface characterization indicates that Ni-based superalloy 617M forms a protective Cr2O3 film during the initial 1000 hours, with minimal metal loss. Prolonged exposure fluxes away Cr from Cr2O3 at the grain boundaries due to the action of low melting alkali metal trisulfate and the localized grain boundary dissolution lead to scale thickening, predominated with Ti diffusion and alumina precipitation enriched along the grain boundaries. Further oxidation showed TiO2 nodule coarsening via Ostwald ripening, creating Cr2−xTi2O3 outward scale, and increased alumina internal oxidation forming an inhomogeneous internal layer, accompanied by voids and intergranular attack. The study proposes fireside Alloy 617M’s corrosion mechanism for assessing long-term durability in AUSC conditions for the first time.