High temperature oxidation of Fe–Cr alloy in O2–H2–H2O atmospheres; microstructure and kinetics
High temperature oxidation of Fe–Cr alloy in O2–H2–H2O atmospheres; microstructure and kinetics
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DOI：
10.1016/s0921-5093(03)00527-6
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发表时间：
2003-11
期刊：
影响因子：
6.4
通讯作者：
L. Mikkelsen;S. Linderoth
中科院分区：
文献类型：
--
作者：
L. Mikkelsen;S. Linderoth
在 1173K 的空气和 7% H2/93% Ar（均含有 1% 或 12% 水蒸气）中检查了合金 Fe0.78Cr0.22 的氧化物微观结构和氧化动力学。在还原条件下生长的氧化铬鳞片上观察到了氧化物晶须和脊，而在空气中生长的氧化铬鳞片中则没有它们。这种差异是由空气中生长的水垢中铬物质的蒸发引起的。讨论了晶须的生长机理。研究发现，在氢气/氩气中生长时，氧化铬鳞片比在空气中生长时能更好地粘附在合金上。这可能是由于在还原条件下清除杂质造成的。鳞片的生长速率与氧活性无关，这可以通过氧化铬鳞片的间隙生长机制来解释。生长速率随着空气中含水量的增加而降低。这是由于生长过程中铬物质从水垢中同时蒸发造成的。与氧化铬垢的稳态生长相反，脱离氧化很大程度上受到反应气氛中氧活性的影响。低氧活度可以保护合金免受在较高氧活度下观察到的灾难性氧化行为。氧活度的调节可能有助于铁铬合金在还原条件下的长期氧化。
The oxide microstructure and oxidation kinetics of the alloy Fe0.78Cr0.22were examined at 1173K in air and in 7% H2/93% Ar, both containing 1 or 12% water vapour. Oxide whiskers and ridges were observed on the chromia scales grown under reducing conditions, while they were absent from the chromia scales grown in air. This difference is caused by vaporization of chromium species from the scale grown in air. The growth mechanism of whiskers is discussed. The chromia scales were found to adhere much better to the alloy when grown in hydrogen/argon than in air. This is probably caused by a scavenge of impurities under reducing conditions. The growth rate of the scales is independent of the oxygen activity, which is explained by an interstitial growth mechanism of the chromia scales. The growth rate decreases with increasing water content in air. This is caused by a simultaneous vaporization of chromium species from the scale during the growth. In contrast to steady-state growth of chromia scales, the breakaway oxidation is highly affected by the oxygen activity in the reaction atmosphere. A low oxygen activity can protect the alloy from the catastrophic oxidation behaviour observed at larger oxygen activities. Tuning of oxygen activity may be useful for long-term oxidation of Fe–Cr alloys under reducing conditions.