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Effects of Water Vapour on the Oxidation of Chromia Formers

Journal Materials Science Forum (Volumes 595 - 598)
Volume High Temperature Corrosion and Protection of Materials 7
Edited by Pierre Steinmetz, Ian G. Wright, Alain Galerie, Daniel Monceau and Stéphane Mathieu
Pages 1189-1197
DOI 10.4028/www.scientific.net/MSF.595-598.1189
Citation David J. Young, 2008, Materials Science Forum, 595-598, 1189
Online since September, 2008
Authors David J. Young
Keywords Chromium, Diffusion, Hydrogen Doping, Oxidation, Volatilisation
Abstract

Water vapour interacts with growing chromia scales in several different ways. Formation and volatilisation of Cr2O2(OH)2 is shown to account quantitatively for chromium loss from thin alloy foils reacted with air-steam mixtures over periods of 103 h. In the shorter term, water vapour is shown to refine the grain structure of Cr2O3 scales grown on Ni-25Cr. Scaling kinetics are at the same time accelerated by an additional, larger contribution to diffusion by a grain boundary species, either OH- or H2O. A slight increase in scaling rate observed at low water vapour partial pressures in H2/H2O gases is thought to be due to hydrogen doping.

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