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<p>The high-temperature oxidation behavior of the TROPEA single-crystal superalloy was investigated in situ via Environmental Scanning Electron Microscopy (ESEM) over 84 h at 910 °C. Following rapid and near-complete surface coverage by (Ni,Co)O oxide, several dynamic phenomena persisted under the experimental conditions. Notably, the growth of NiO crystals and the migration of bright surface regions were systematically observed. Post-mortem surface and cross-sectional analyses revealed that these bright areas corresponded to tantalum enrichment, forming a continuous Cr–Ta–Ti–O-rich oxide layer at the alloy–oxide interface. The presence of these regions thus serves as a surface indicator of subsurface interfacial processes. The frequency of bright area formation diminished over time, consistent with diffusion-limited oxidation kinetics. Persistent oxidation of Ni and Ta after 84&#xa0;h confirms that the alloy remains in a transient oxidation regime under these conditions, as polished cross-sections revealed no continuous alumina layer capable of passivating less noble elements.</p>

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Ni-Based Single Crystal Superalloy Oxidation Studied by High Temperature Environmental Scanning Electron Microscopy. Part 2. Formation and Stabilization of the Oxide Layer

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • R. Podor,
  • J. Lautru,
  • L. Hunault,
  • F. Pedraza,
  • J. Cormier,
  • L. Aranda,
  • M. Vilasi,
  • S. Mathieu

摘要

The high-temperature oxidation behavior of the TROPEA single-crystal superalloy was investigated in situ via Environmental Scanning Electron Microscopy (ESEM) over 84 h at 910 °C. Following rapid and near-complete surface coverage by (Ni,Co)O oxide, several dynamic phenomena persisted under the experimental conditions. Notably, the growth of NiO crystals and the migration of bright surface regions were systematically observed. Post-mortem surface and cross-sectional analyses revealed that these bright areas corresponded to tantalum enrichment, forming a continuous Cr–Ta–Ti–O-rich oxide layer at the alloy–oxide interface. The presence of these regions thus serves as a surface indicator of subsurface interfacial processes. The frequency of bright area formation diminished over time, consistent with diffusion-limited oxidation kinetics. Persistent oxidation of Ni and Ta after 84 h confirms that the alloy remains in a transient oxidation regime under these conditions, as polished cross-sections revealed no continuous alumina layer capable of passivating less noble elements.