Exploring failure modes of alumina scales on FeCrAl and FeNiCrAl alloys in a nitriding environment

A. N. Mortazavi, M. Esmaily, C. Geers, N. Birbilis, Jan-Erik Svensson, M. Halvarsson, D. Chandrasekaran, L. G. Johansson

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Two high-temperature FeCrAl and FeNiCrAl alloys were exposed in a strongly nitriding environment at 900 °C and the morphology of nitridation was studied. Quasi-in-situ experiments revealed that nitridation started at specific surface sites directly related to the alloy microstructure where the alumina scale was permeable to nitrogen. FeCrAl alloy grains with (112) orientation formed outward-growing alumina scales and were susceptible to nitridation. Outward-growing scales and substrate nitridation was also observed at chromium carbide precipitates in the FeNiCrAl alloy. Both alloys suffered nitridation at reactive element-rich (Y and Zr) inclusions larger than a certain critical size. The latter type of attack is caused by cracks and pores in the scale. The findings open new avenues of research for developing the next generation of high temperature alloys with superior properties.

Original languageEnglish
Pages (from-to)131-146
Number of pages16
JournalActa Materialia
Volume201
DOIs
Publication statusPublished - Dec 2020
Externally publishedYes

Keywords

  • Alumina scale failure
  • Crystallographic orientation
  • High temperature oxidation
  • Nitridation
  • Reactive elements

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