Journal Article

PreJuSER-12260

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Oxidation Kinetics of Y-doped FeCrAl-Alloys in Low and High pO2 Gases

Young, D. J. ; Naumenko, D.FZJ* ; Niewolak, L.FZJ* ; Wessel, E.FZJ* ; Singheiser, L.FZJ* ; Quadakkers, W. J.FZJ*

2010
Wiley-VCH Weinheim [u.a.]

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Please use a persistent id in citations: doi:10.1002/maco.200905432

Abstract: A model Fe-20Cr-5Al-0.05Y alloy was oxidized in Ar-20%O-2 and Ar-4%H-2-7%H2O at 1200-1300 degrees C. Two-stage oxidation experiments using oxygen isotope tracers showed that inward oxygen diffusion was predominant in both gases, but more isotope exchange was observed in the H-2/H2O gas reaction. The alumina scales formed in both gases were composed of columnar grains, the lateral size of which increased linearly with depth beneath the scale surface. Thermogravimetric measurement of oxygen uptake revealed kinetics which were intermediate to parabolic and cubic kinetic rate laws. A model based on grain boundary diffusion control coupled with competitive oxide grain growth accounts satisfactorily for the results when the requirement for a divergence-free flux within the scale is imposed. This treatment shows that the oxide grain boundary diffusion coefficient is lower when H2O is the oxidant. It is concluded that hydrogen slows the grain boundary diffusion process by altering the nature of the diffusing species.

Keyword(s): J

Note: The authors are grateful to Mr. H. Cosler at the Forschungszentrum Julich for thermogravimetry measurements and two-stage oxidation experiments. Part of the work was performed under the funding of the European Commission (Project acronym SMILER, G5RD-CT-2001-0530) and Deutsche Forschungsgemeinshaft (Project No. NA-615-2).

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Research Program(s):

1. Rationelle Energieumwandlung (P12)

Appears in the scientific report 2010

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