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Alfred Larsson. Portrait.

Alfred Larsson

Postdoctoral fellow

Alfred Larsson. Portrait.

Thickness and composition of native oxides and near-surface regions of Ni superalloys

Author

  • Alfred Larsson
  • Giulio D'Acunto
  • Mariya Vorobyova
  • Giuseppe Abbondanza
  • Ulrich Lienert
  • Zoltan Hegedüs
  • Alexei Preobrajenski
  • Lindsay R. Merte
  • Josefin Eidhagen
  • Anna Delblanc
  • Jinshan Pan
  • Edvin Lundgren
Show all

Summary, in English

The surface chemistry and thickness of the native oxide, hydroxide, and modified sub-surface layer of three Ni superalloys (alloy 59, 625, and 718) were determined by synchrotron X-ray Photoelectron Spectroscopy (XPS) and X-ray Reflectivity (XRR). Taking advantage of the synchrotron radiation techniques, a procedure for normalizing the photoelectron intensity was employed, which allowed for accurate quantitative analysis revealing a total oxide thickness for all samples of 12–13 Å, a hydroxide layer of 2–3 Å, and a thickness of the sub-surface alloy layer of 20–35 Å. The thickness results were compared to structural atomic models suggesting that the oxide thickness corresponds to four planes of metal cations in the oxide matrix. The XPS data revealed that the native oxides were enriched in Cr3+, Mo(4,5,6)+, and Nb5+, while no Ni oxide was detected. The hydroxide layer mainly contained Ni2+ and Cr3+ hydroxide. The sub-surface layer was enriched in Ni and depleted in Cr, Fe, Mo, and Nb. The obtained oxide composition can be explained using thermodynamics, and it was found that the oxide composition correlates with the enthalpy of oxide formation for the metal elements in the alloys. Finally, the advantages of synchrotron radiation for composition and thickness determination are discussed.

Department/s

  • Synchrotron Radiation Research
  • NanoLund: Centre for Nanoscience
  • MAX IV Laboratory

Publishing year

2022-02-25

Language

English

Publication/Series

Journal of Alloys and Compounds

Volume

895

Document type

Journal article

Publisher

Elsevier

Topic

  • Materials Chemistry

Keywords

  • Corrosion
  • Cr
  • Fe
  • Mo
  • Native oxide
  • Nb
  • Ni
  • Nickel alloy
  • Oxide
  • Passive film
  • Superalloy
  • Synchrotron
  • X-ray photoelectron spectroscopy
  • X-ray reflectivity
  • XPS
  • XRR

Status

Published

ISBN/ISSN/Other

  • ISSN: 0925-8388