Phase determination and microstructure of oxide scales formed on steel at high temperature

G. D. West*, S. Birosca, R. L. Higginson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Even in simple low-alloy steels the oxide scales that form during hot working processes are often a complex mixture of three iron oxide phases: haematite, magnetite and wüstite. The mechanical properties, and hence descalability, are intimately linked with phase distribution and microstructure, which in turn are sensitive to both steel composition and oxidation conditions. In this study electron backscatter diffraction in the SEM has been used to characterize the microstructures of oxide scales formed on two compositions of low-alloy steel. The technique can unambiguously differentiate between the candidate phases to provide the phase distribution within the scale. This is used to investigate grain orientation relationships both within and between phase layers. It has been found that the strength of the orientational relationship between the magnetite and wüstite layers is dependent on steel composition, and in particular Si content. In a low-Si (0.01 wt%) alloy only a very weak relationship was found to exist for a range of oxidation temperatures (800-1000 °C), whereas for the higher Si (0.3 7 wt%) alloy a strong relationship was observed under the same oxidation conditions. These orientational relationships are particularly important because, in this temperature range, the majority of oxide scale growth occurs at the magnetite/wüstite interphase boundary.

Original languageEnglish
Pages (from-to)122-129
Number of pages8
JournalJournal of Microscopy
Volume217
Issue number2
DOIs
Publication statusPublished - 1 Feb 2005

Keywords

  • EBSD
  • Microtexture
  • Oxide scale
  • Phase differentiation
  • Steel

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