Oxidation of FeCrAl alloys at 500-900 degrees C in dry O-2
Artikel i vetenskaplig tidskrift, 2005

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.

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KeyWords Plus: ALUMINA SCALES

Författare

Helena Josefsson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Fang Liu

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Jan-Erik Svensson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Mats Halvarsson

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Lars-Gunnar Johansson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

MATERIALS AND CORROSION-WERKSTOFFE UND KORROSION 56 (11): 801-805 NOV 2005

0947-5117 (ISSN)

Vol. 56(11) 801-805

Ämneskategorier

Miljövetenskap