Oxidation of FeCrAl alloys at 500-900 °C in dry O2
Oxidation of FeCrAl alloys at 500-900 °C in dry O2
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DOI：
10.1002/maco.200503882
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发表时间：
2005-11-01
影响因子：
1.8
通讯作者：
Johansson, LG
中科院分区：
文献类型：
--
作者：
Josefsson, H;Liu, F;Johansson, LG
本文报道了一种商用FeCrAl合金Kanthal AF在500-900 ℃温度范围内的氧化。使用热天平将样品等温暴露在干燥氧气中长达72小时。此外，在管式炉中进行168小时暴露。通过掠角X射线衍射（XRD）、扫描电子显微镜/能量色散X射线分析（SEM/EDX）和俄歇电子能谱（AES）对暴露样品进行了研究。在所有暴露温度下，样品表面的大部分被薄而光滑的基底氧化物覆盖。此外，富稀土颗粒，具有1-3 μ m的典型尺寸的形式。在800和900摄氏度的厚氧化物补丁出现，具有位于基础氧化物顶部的针状微晶。厚的氧化物通常在富Y氧化物颗粒周围形成。氧化物中铁和铬的浓度随温度的升高而降低。XRD证明在700 ℃下已经形成了α-Al 2 O3。α-Al 2 O3形成的低温归因于初始氧化物中存在铬。有人建议，促进表面上的同质结构的埃科莱特，（Cr2 O3）组成的Cr2 O3形核。在900 ℃下暴露后，AES显示氧化物的外部部分中有大量的Mg，通过XRD检测到MgAl 2 O 4以及γ-和α-Al 2 O3。
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.