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Dynamics of early-stage oxide formation on a Ni-Cr-Mo alloy

Larsson, Alfred LU ; Gericke, Sabrina LU ; Grespi, Andrea LU ; Koller, Volkmar ; Eidhagen, Josefin ; Yue, Xiaoqi ; Frampton, Eleanor LU ; Appelfeller, Stephan LU ; Generalov, Alexander LU and Preobrajenski, Alexei LU , et al. (2024) In npj Materials Degradation 8(1).
Abstract

Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 °C. Cr and Mo begin to oxidize immediately after exposure to O2, and Cr3+, Mo4+, and Mo6+ oxides are formed. In contrast, Ni does... (More)

Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 °C. Cr and Mo begin to oxidize immediately after exposure to O2, and Cr3+, Mo4+, and Mo6+ oxides are formed. In contrast, Ni does not contribute significantly to the oxide film. A self-limiting oxide thickness, which did not depend on temperature below 400 °C, is observed. This is attributed to the consumption of available Cr and Mo near the surface, which results in an enrichment of metallic Ni under the oxide. The self-limited oxide thickness is 6–8 Å, which corresponds to 3–4 atomic layers of cations in the oxide. At 400 °C, sublimation of Mo6+ oxide is observed, resulting in the formation of an almost pure layer of Cr2O3 on the alloy surface. Lastly, a mechanism is presented that explains the formation of the bi-layer oxide structure observed for Ni-Cr-Mo alloys, which involves the enhanced migration of hexavalent Mo ions in the electric field, which drives mass transport during oxidation according to both the Cabrera Mott model and the Point Defect Model.

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publishing date
type
Contribution to journal
publication status
published
subject
in
npj Materials Degradation
volume
8
issue
1
article number
39
publisher
Nature Publishing Group
external identifiers
  • scopus:85190536453
ISSN
2397-2106
DOI
10.1038/s41529-024-00463-9
language
English
LU publication?
yes
id
d34bfd4a-4ae5-44f2-9935-294e6ef24f32
date added to LUP
2024-04-29 13:58:49
date last changed
2024-04-29 13:59:24
@article{d34bfd4a-4ae5-44f2-9935-294e6ef24f32,
  abstract     = {{<p>Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 °C. Cr and Mo begin to oxidize immediately after exposure to O<sub>2</sub>, and Cr<sup>3+</sup>, Mo<sup>4+</sup>, and Mo<sup>6+</sup> oxides are formed. In contrast, Ni does not contribute significantly to the oxide film. A self-limiting oxide thickness, which did not depend on temperature below 400 °C, is observed. This is attributed to the consumption of available Cr and Mo near the surface, which results in an enrichment of metallic Ni under the oxide. The self-limited oxide thickness is 6–8 Å, which corresponds to 3–4 atomic layers of cations in the oxide. At 400 °C, sublimation of Mo<sup>6+</sup> oxide is observed, resulting in the formation of an almost pure layer of Cr<sub>2</sub>O<sub>3</sub> on the alloy surface. Lastly, a mechanism is presented that explains the formation of the bi-layer oxide structure observed for Ni-Cr-Mo alloys, which involves the enhanced migration of hexavalent Mo ions in the electric field, which drives mass transport during oxidation according to both the Cabrera Mott model and the Point Defect Model.</p>}},
  author       = {{Larsson, Alfred and Gericke, Sabrina and Grespi, Andrea and Koller, Volkmar and Eidhagen, Josefin and Yue, Xiaoqi and Frampton, Eleanor and Appelfeller, Stephan and Generalov, Alexander and Preobrajenski, Alexei and Pan, Jinshan and Over, Herbert and Lundgren, Edvin}},
  issn         = {{2397-2106}},
  language     = {{eng}},
  number       = {{1}},
  publisher    = {{Nature Publishing Group}},
  series       = {{npj Materials Degradation}},
  title        = {{Dynamics of early-stage oxide formation on a Ni-Cr-Mo alloy}},
  url          = {{http://dx.doi.org/10.1038/s41529-024-00463-9}},
  doi          = {{10.1038/s41529-024-00463-9}},
  volume       = {{8}},
  year         = {{2024}},
}