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Oxidation of Metals

, Volume 31, Issue 5–6, pp 369–391 | Cite as

Comparison of the effects of small additions of silicon or aluminum on the oxidation of iron-chromium alloys

  • F. H. Stott
  • F. I. Wei
Article

Abstract

A study has been undertaken of the oxidation behavior of Fe-26 wt.% Cr-1 wt.% Al and Fe-26 wt.% Cr-1 wt.% Si at 800° and 1000°C in oxygen, in order to determine the usefulness of the two tertiary elements in facilitating the development of the Cr2O3 external scale. The research has also permitted a comparison of the modes of internal oxidation of these elements, with a view to ascertaining the ease of establishment of the tertiary element oxides as healing layers at the scale/alloy interface. It has been shown that aluminum is the more effective addition in this respect, due to formation of a higher population density of internal oxide nuclei in the early stages. However, in the 1% Al alloy, the precipitates penetrate inward, to considerable depths, as continuous platelets, making development of a complete healing layer difficult. In practice, a higher aluminum concentration is necessary for the closely spaced precipitates to coalesce to form the healing layer, but the process then occurs rapidly. The initial internal oxide nuclei in the 1% Si alloy have a much smaller population density and are restricted to a location very close to the surface. Thus, a healing layer can be established, but the large interparticle spacing makes this a very slow process. Even at a higher silicon concentration, it takes a significant period to be completed. The effects are discussed and accounted for, particularly in terms of the relative stabilities of the various oxides.

Key words

internal oxidation silica alumina iron-chromium alloys 

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Copyright information

© Plenum Publishing Corporation 1989

Authors and Affiliations

  • F. H. Stott
    • 1
  • F. I. Wei
    • 2
  1. 1.Corrosion and Protection CentreUniversity of Manchester Institute of Science and TechnologyManchesterEngland
  2. 2.Research and Development DepartmentChina Steel CorporationKaohsiungTaiwan, Republic of China

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