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Corrosion of alloy 800 exposed to high temperature helium.

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Title: Corrosion of alloy 800 exposed to high temperature helium.
Authors: Coghlan, Lawrence1 (AUTHOR) Lawrence.coghlan@bristol.ac.uk, Burrows, Robert2 (AUTHOR), Clark, Ronald N.2 (AUTHOR), Kumar, David2 (AUTHOR), Zimina, Mariia1 (AUTHOR), Shin, Aya3 (AUTHOR), Hawes, Jonathan2 (AUTHOR), Martin, Tomas1 (AUTHOR)
Source: Journal of Nuclear Materials. Feb2026, Vol. 620, pN.PAG-N.PAG. 1p.
Subjects: Heat resistant alloys, Nuclear reactor materials, Helium, Surface analysis, Metallurgical segregation, Steel corrosion, Phase diagrams, Oxidation
Abstract: • High temperature helium exposure leads to the formation of non-uniform surface corrosion layer on Alloy 800. • Elemental segregation occurs after <150 h of exposure, particularly Cr. • An Mn-rich oxide layer (with Cr) begins to form after 1000 h exposure. • Formation of corrosion layers follows Ellingham Diagram thermodynamic predictions. Alloy 800 is currently being considered as a suitable alloy for use within the next generation of High Temperature Gas Cooled Reactors (HTGRs). These reactors will operate using Helium as the heat transfer gas at temperatures of 700 °C and higher. HTGR materials need to be able to withstand these high temperatures over service lives of multiple decades in the presence of helium and impurities present either within the gas or from ingress to the system. This work exposed Alloy 800 at 750 °C in a helium atmosphere for up to 1000 h and characterised the materials using advanced microscopy techniques. Within the bulk material, Mn and Cr segregation to the grain boundaries took place at <150 h of exposure due to the high temperature and similar segregation was seen towards the surface, both along grain boundaries and within grains. A non-uniform Cr- and Mn-rich oxide forms on the surface of Alloy 800 after 150 h with the uniformity and thickness increasing with exposure duration. Al, Ti, Si and Mn are all seen to oxidise ahead of the bulk material and before Cr, with the development of an Al-rich internal oxidation zone and the formation of a non-uniform Mn-rich oxide forming at the surface of the alloy. Cr later migrates to the surface and forms part of this oxide. The thermodynamics of the oxidation reactions are in agreement with Ellingham diagram predictions with the alloying elements oxidising in order of stability. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Nuclear Materials is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Corrosion of alloy 800 exposed to high temperature helium.
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  Data: &lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Coghlan%2C+Lawrence%22&quot;&gt;Coghlan, Lawrence&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)&lt;i&gt; Lawrence.coghlan@bristol.ac.uk&lt;/i&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Burrows%2C+Robert%22&quot;&gt;Burrows, Robert&lt;/searchLink&gt;&lt;relatesTo&gt;2&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Clark%2C+Ronald+N%2E%22&quot;&gt;Clark, Ronald N.&lt;/searchLink&gt;&lt;relatesTo&gt;2&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Kumar%2C+David%22&quot;&gt;Kumar, David&lt;/searchLink&gt;&lt;relatesTo&gt;2&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Zimina%2C+Mariia%22&quot;&gt;Zimina, Mariia&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Shin%2C+Aya%22&quot;&gt;Shin, Aya&lt;/searchLink&gt;&lt;relatesTo&gt;3&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Hawes%2C+Jonathan%22&quot;&gt;Hawes, Jonathan&lt;/searchLink&gt;&lt;relatesTo&gt;2&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Martin%2C+Tomas%22&quot;&gt;Martin, Tomas&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)
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  Data: &lt;searchLink fieldCode=&quot;JN&quot; term=&quot;%22Journal+of+Nuclear+Materials%22&quot;&gt;Journal of Nuclear Materials&lt;/searchLink&gt;. Feb2026, Vol. 620, pN.PAG-N.PAG. 1p.
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– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: • High temperature helium exposure leads to the formation of non-uniform surface corrosion layer on Alloy 800. • Elemental segregation occurs after &lt;150 h of exposure, particularly Cr. • An Mn-rich oxide layer (with Cr) begins to form after 1000 h exposure. • Formation of corrosion layers follows Ellingham Diagram thermodynamic predictions. Alloy 800 is currently being considered as a suitable alloy for use within the next generation of High Temperature Gas Cooled Reactors (HTGRs). These reactors will operate using Helium as the heat transfer gas at temperatures of 700 &#176;C and higher. HTGR materials need to be able to withstand these high temperatures over service lives of multiple decades in the presence of helium and impurities present either within the gas or from ingress to the system. This work exposed Alloy 800 at 750 &#176;C in a helium atmosphere for up to 1000 h and characterised the materials using advanced microscopy techniques. Within the bulk material, Mn and Cr segregation to the grain boundaries took place at &lt;150 h of exposure due to the high temperature and similar segregation was seen towards the surface, both along grain boundaries and within grains. A non-uniform Cr- and Mn-rich oxide forms on the surface of Alloy 800 after 150 h with the uniformity and thickness increasing with exposure duration. Al, Ti, Si and Mn are all seen to oxidise ahead of the bulk material and before Cr, with the development of an Al-rich internal oxidation zone and the formation of a non-uniform Mn-rich oxide forming at the surface of the alloy. Cr later migrates to the surface and forms part of this oxide. The thermodynamics of the oxidation reactions are in agreement with Ellingham diagram predictions with the alloying elements oxidising in order of stability. [ABSTRACT FROM AUTHOR]
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  Data: &lt;i&gt;Copyright of Journal of Nuclear Materials is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder&#39;s express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.&lt;/i&gt; (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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    Identifiers:
      – Type: doi
        Value: 10.1016/j.jnucmat.2025.156333
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 1
        StartPage: N.PAG
    Subjects:
      – SubjectFull: Heat resistant alloys
        Type: general
      – SubjectFull: Nuclear reactor materials
        Type: general
      – SubjectFull: Helium
        Type: general
      – SubjectFull: Surface analysis
        Type: general
      – SubjectFull: Metallurgical segregation
        Type: general
      – SubjectFull: Steel corrosion
        Type: general
      – SubjectFull: Phase diagrams
        Type: general
      – SubjectFull: Oxidation
        Type: general
    Titles:
      – TitleFull: Corrosion of alloy 800 exposed to high temperature helium.
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              M: 02
              Text: Feb2026
              Type: published
              Y: 2026
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              Value: 620
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            – TitleFull: Journal of Nuclear Materials
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