Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation

Norinsan Kamil Othman, J. Zhang, D. J. Young

Research output: Contribution to journalArticle

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Abstract

Three Fe-Cr model alloys (Cr: 9, 17, and 25 wt%) were subjected to cyclic oxidation in Ar-10%H2-5%H2O (pO2=3.6x10-22 atm), Ar-20%O2 and Ar-20%O2-5%H2O atmospheres at 700 °C. In general, increasing alloy chromium levels reduced the oxidation rate. At high p02, in the absence of water vapour, the 9%Cr alloy exhibited breakaway oxidation at the beginning of the reaction. However, for chromium levels>17%, no breakaway oxidation occurred, and the weight gain was very low. Adding water vapour to Ar-20%O2 accelerated the oxidation of alloys containing 17% Cr or less. However, this accelerating effect was not evident for high chromium alloys. At low p02, breakaway oxidation of alloys with chromium concentration ≤ 17% occurred after 300 cycles exposure. High chromium content alloys did not undergo significant oxidation. XRD analysis showed that for low chromium content alloys (Cr<17%), spinel and wustite were formed in the low p02 gas, while in the high p02 gas, hematite, magnetite and spinel were produced. In the case of high chromium alloys, only Cr2O3 was detected. Metallographic examination showed that the spinel was present in the form of internal precipitates. A dense chromia layer was observed at alloy chromium levels above 25%. The reasons for the difference in oxidation behaviour at different oxygen potentials, and the effect of water vapour are discussed in connection with the microstructure of the oxides.

Original languageEnglish
Pages (from-to)315
Number of pages1
JournalJournal of the Chinese Society of Corrosion and Protection
Volume29
Issue number4
Publication statusPublished - 2009
Externally publishedYes

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Chromium Alloys
Chromium alloys
Oxidation
Kinetics
Chromium
Steam
Water vapor
Gases
Ferrosoferric Oxide
Hematite
Magnetite
Oxides
Precipitates
Oxygen
Microstructure

ASJC Scopus subject areas

  • Engineering(all)
  • Materials Science(all)

Cite this

Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation. / Othman, Norinsan Kamil; Zhang, J.; Young, D. J.

In: Journal of the Chinese Society of Corrosion and Protection, Vol. 29, No. 4, 2009, p. 315.

Research output: Contribution to journalArticle

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