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Oxidation of FeCrAl alloys at 500-900 degrees C in dry O-2

Helena Josefsson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Fang Liu (Institutionen för teknisk fysik, Mikroskopi och mikroanalys) ; Jan-Erik Svensson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Mats Halvarsson (Institutionen för teknisk fysik, Mikroskopi och mikroanalys) ; Lars-Gunnar Johansson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi)
MATERIALS AND CORROSION-WERKSTOFFE UND KORROSION 56 (11): 801-805 NOV 2005 (ISSN: 0947-5117 ). Vol. 56(11) (2005), p. 801-805.
[Artikel, refereegranskad vetenskaplig]

This paper reports on the oxidation of a commercial FeCrAl alloy, Kanthal AF, in the temperature range 500-900 degrees C. The samples are exposed isothermally in dry oxygen for up to 72 h using a thermo-balance. In addition, 168 h exposures are carried out in a tube furnace. The exposed samples are investigated by grazing angle Xray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), and auger electron spectroscopy (AES). The rate of oxidation increases with temperature, the kinetics being parabolic in the range 700-900 degrees C. At all exposure temperatures, most of the sample surface is covered by a thin smooth base oxide. In addition, RE-rich particles, with a typical size of 1-3 mu m form. At 800 and 900 degrees C patches of thick oxide appear, featuring needle-formed crystallites situated on top of the base oxide. The thick oxide usually forms around Y-rich oxide particles. The concentration of iron and chromium in the oxide decreases with increasing temperature. XRD proves the formation of alpha-Al2O3 already at 700 degrees C, The low temperature of formation of alpha-Al2O3 is attributed to the presence of chromium in the initial oxide. It is proposed that corundum nucleation is facilitated on a surface consisting of the isostructural escolaite, (Cr2O3). After exposure at 900 degrees C AES shows large amounts of Mg in the outer part of the oxide, MgAl2O4 being detected by XRD together with gamma- and alpha-Al2O3.

Nyckelord: KeyWords Plus: ALUMINA SCALES; FOIL; BEHAVIOR; YTTRIUM; GROWTH


Addresses: Josefsson H (reprint author), Chalmers Univ Technol, High Temp Corros Ctr, Gothenburg, S-41296 Sweden Chalmers Univ Technol, High Temp Corros Ctr, Gothenburg, S-41296 Sweden Chalmers Univ Technol, Dept Environm Inorgan Chem & Expt Phys, Gothenburg, S-41296 Sweden E-mail Addresses: helenaj@chem.chalmers.se



Denna post skapades 2006-01-19.
CPL Pubid: 12107

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)
Institutionen för teknisk fysik, Mikroskopi och mikroanalys (2005-2012)

Ämnesområden

Miljökemi

Chalmers infrastruktur