Effect of water vapour on cyclic oxidation of Fe–Cr alloys / N. K. Othman in Materials and corrosion, Vol. 62 N° 6 (Juin 2011)  

Public ISBD [article]  inMaterials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 496–503 Titre : Effect of water vapour on cyclic oxidation of Fe–Cr alloys Type de document : texte imprimé Auteurs : N. K. Othman, Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur Année de publication : 2011 Article en page(s) : pp. 496–503 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Alloy depletion Breakaway Cyclic oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model Fe–Cr alloys containing 9, 17 or 25 wt% Cr were subjected to repeated 1 h cycles of exposure at 700 °C to flowing gas mixtures of Ar-20O2, Ar-20O2-5H2O and Ar-5O2-20H2O (all in volume %) for up to 400 cycles. The kinetics and morphological development of these reactions were compared with those found during isothermal exposure to the same gases. Under isothermal conditions, all alloys developed thin protective chromium-rich scales in dry oxygen. Addition of 5% H2O induced breakaway for Fe-9Cr within 48 h, but had little effect on higher chromium alloys. Isothermal chromia scale growth on Fe-17Cr and Fe-25Cr was accelerated by the addition of 20% H2O, but breakaway did not result. Under cyclic conditions in dry oxygen, Fe-9Cr quickly entered breakaway, oxidising according to fast, linear kinetics, but the higher chromium alloys exhibited protective behaviour. When 5% H2O was added to the oxygen, the 17% Cr alloy also underwent fast breakaway oxidation, but Fe-25Cr continued to be protected by a chromia scale. In the 20% H2O gas, all alloys failed under cyclic conditions, producing thick, iron-rich oxide scales. The synergistic effects of water vapour and temperature cycling are discussed in terms of alloy chromium depletion and the effects of H2O(g) on oxide transport properties. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005866/abstract [article] Effect of water vapour on cyclic oxidation of Fe–Cr alloys [texte imprimé] / N. K. Othman, Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur . - 2011 . - pp. 496–503. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 496–503 Mots-clés : Alloy depletion Breakaway Cyclic oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model Fe–Cr alloys containing 9, 17 or 25 wt% Cr were subjected to repeated 1 h cycles of exposure at 700 °C to flowing gas mixtures of Ar-20O2, Ar-20O2-5H2O and Ar-5O2-20H2O (all in volume %) for up to 400 cycles. The kinetics and morphological development of these reactions were compared with those found during isothermal exposure to the same gases. Under isothermal conditions, all alloys developed thin protective chromium-rich scales in dry oxygen. Addition of 5% H2O induced breakaway for Fe-9Cr within 48 h, but had little effect on higher chromium alloys. Isothermal chromia scale growth on Fe-17Cr and Fe-25Cr was accelerated by the addition of 20% H2O, but breakaway did not result. Under cyclic conditions in dry oxygen, Fe-9Cr quickly entered breakaway, oxidising according to fast, linear kinetics, but the higher chromium alloys exhibited protective behaviour. When 5% H2O was added to the oxygen, the 17% Cr alloy also underwent fast breakaway oxidation, but Fe-25Cr continued to be protected by a chromia scale. In the 20% H2O gas, all alloys failed under cyclic conditions, producing thick, iron-rich oxide scales. The synergistic effects of water vapour and temperature cycling are discussed in terms of alloy chromium depletion and the effects of H2O(g) on oxide transport properties. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005866/abstract

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