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Oxidation kinetics of Y-doped FeCrAl-alloys in low and high pO2 gases / D. J. Young in Materials and corrosion, Vol. 61 N° 10 (Octobre 2010) 

Public ISBD [article]  in Materials and corrosion > Vol. 61 N° 10 (Octobre 2010) . - pp. 838–844 Titre : Oxidation kinetics of Y-doped FeCrAl-alloys in low and high pO2 gases Type de document : texte imprimé Auteurs : D. J. Young, Auteur ; D. Naumenko, Auteur ; L. Niewolak, Auteur Année de publication : 2011 Article en page(s) : pp. 838–844 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Alumina  scales;  grain  boundary  diffusion;  FeCrAlY  alloy;  oxidation  kinetics Résumé : A model Fe-20Cr-5Al-0.05Y alloy was oxidized in Ar-20%O2 and Ar-4%H2-7%H2O at 1200–1300 °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 H2/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. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905432/abstract [article] Oxidation kinetics of Y-doped FeCrAl-alloys in low and high pO2 gases [texte imprimé] / D. J. Young, Auteur ; D. Naumenko, Auteur ; L. Niewolak, Auteur . - 2011 . - pp. 838–844. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 61 N° 10 (Octobre 2010) . - pp. 838–844 Mots-clés : Alumina  scales;  grain  boundary  diffusion;  FeCrAlY  alloy;  oxidation  kinetics Résumé : A model Fe-20Cr-5Al-0.05Y alloy was oxidized in Ar-20%O2 and Ar-4%H2-7%H2O at 1200–1300 °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 H2/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. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.200905432/abstract