Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Three Fe-Cr model alloys (Cr: 9, 17, and 25 wt %) were subjected to cyclic oxidation in Ar-10%H 2-5%H 2O (p O2= 3.6 x 10 -22 atm), Ar-20%O 2 and Ar-20%O 2-5%H 2O atmospheres at 700°C. In general, increasing alloy chromium levels reduced the oxidation rate. At high p O2, in the absence of water vapour, the 9%Cr alloy exhibited breakaway oxidation at the early stage 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%O 2 accelerated the oxidation of alloys containing ≤17% Cr. However, this accelerating effect was not evident for Fe25Cr alloy. At low p O2, breakaway oxidation of alloys with chromium concentration ≤ 17% occurred after 300 cycles. Fe25Cr alloy did not undergo significant oxidation. XRD and metallographic analyses showed that for Fe25Cr alloy, a thin Cr 2O 3 layer was formed. However, for other low chromium content, hematite, magnetite and spinel (FeCr 2O 4) were also detected in the form of different layers in the thick oxide scale. An internal oxide zone with spinel was also formed for these low Cr alloys. Morphologies and growth kinetics of these oxides varied with the alloy composition and reaction condition. The variation of this oxidation behaviour at different oxygen potentials, and the effect of water vapour were discussed in connection with the microstructure of the oxides.

Original languageEnglish
Title of host publication48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008
Pages485-495
Number of pages11
Publication statusPublished - 2008
Externally publishedYes
Event48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008 - Wellington
Duration: 16 Nov 200819 Nov 2008

Other

Other48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008
CityWellington
Period16/11/0819/11/08

Fingerprint

oxidation
kinetics
boundary layer separation
water vapor
chromium
oxides
spinel
chromium alloys
hematite
magnetite
atmospheres
microstructure
cycles
oxygen

Keywords

  • Breakaway oxidation
  • Cr O
  • Fe-Cr alloys
  • Internal oxidation
  • Water vapour

ASJC Scopus subject areas

  • Surfaces and Interfaces

Cite this

Othman, N. K., Zhang, J., & Young, D. J. (2008). Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation. In 48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008 (pp. 485-495)

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

48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008. 2008. p. 485-495.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Othman, NK, Zhang, J & Young, DJ 2008, Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation. in 48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008. pp. 485-495, 48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008, Wellington, 16/11/08.
Othman NK, Zhang J, Young DJ. Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation. In 48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008. 2008. p. 485-495
Othman, Norinsan Kamil ; Zhang, J. ; Young, D. J. / Kinetic and microstructural analyses of chromia forming alloys during cyclic oxidation. 48th Annual Conference of the Australasian Corrosion Association 2008: Corrosion and Prevention 2008. 2008. pp. 485-495
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N2 - Three Fe-Cr model alloys (Cr: 9, 17, and 25 wt %) were subjected to cyclic oxidation in Ar-10%H 2-5%H 2O (p O2= 3.6 x 10 -22 atm), Ar-20%O 2 and Ar-20%O 2-5%H 2O atmospheres at 700°C. In general, increasing alloy chromium levels reduced the oxidation rate. At high p O2, in the absence of water vapour, the 9%Cr alloy exhibited breakaway oxidation at the early stage 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%O 2 accelerated the oxidation of alloys containing ≤17% Cr. However, this accelerating effect was not evident for Fe25Cr alloy. At low p O2, breakaway oxidation of alloys with chromium concentration ≤ 17% occurred after 300 cycles. Fe25Cr alloy did not undergo significant oxidation. XRD and metallographic analyses showed that for Fe25Cr alloy, a thin Cr 2O 3 layer was formed. However, for other low chromium content, hematite, magnetite and spinel (FeCr 2O 4) were also detected in the form of different layers in the thick oxide scale. An internal oxide zone with spinel was also formed for these low Cr alloys. Morphologies and growth kinetics of these oxides varied with the alloy composition and reaction condition. The variation of this oxidation behaviour at different oxygen potentials, and the effect of water vapour were discussed in connection with the microstructure of the oxides.

AB - Three Fe-Cr model alloys (Cr: 9, 17, and 25 wt %) were subjected to cyclic oxidation in Ar-10%H 2-5%H 2O (p O2= 3.6 x 10 -22 atm), Ar-20%O 2 and Ar-20%O 2-5%H 2O atmospheres at 700°C. In general, increasing alloy chromium levels reduced the oxidation rate. At high p O2, in the absence of water vapour, the 9%Cr alloy exhibited breakaway oxidation at the early stage 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%O 2 accelerated the oxidation of alloys containing ≤17% Cr. However, this accelerating effect was not evident for Fe25Cr alloy. At low p O2, breakaway oxidation of alloys with chromium concentration ≤ 17% occurred after 300 cycles. Fe25Cr alloy did not undergo significant oxidation. XRD and metallographic analyses showed that for Fe25Cr alloy, a thin Cr 2O 3 layer was formed. However, for other low chromium content, hematite, magnetite and spinel (FeCr 2O 4) were also detected in the form of different layers in the thick oxide scale. An internal oxide zone with spinel was also formed for these low Cr alloys. Morphologies and growth kinetics of these oxides varied with the alloy composition and reaction condition. The variation of this oxidation behaviour at different oxygen potentials, and the effect of water vapour were discussed in connection with the microstructure of the oxides.

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