Enhanced oxidation of the 9%Cr steel P91 in water vapour containing environments
Enhanced oxidation of the 9%Cr steel P91 in water vapour containing environments
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DOI：
10.1016/j.corsci.2006.02.002
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发表时间：
2006-11-01
影响因子：
8.3
通讯作者：
Quadakkers, W. J.
中科院分区：
文献类型：
--
作者：
Ehlers, J.;Young, D. J.;Quadakkers, W. J.
研究了9%Cr钢P91在650℃、含氧量相对较低(1%)的N-2-O-2-H2O混合气体中的短期氧化行为。用(H2O)-O-18-示踪剂研究了氧化膜的生长机理，并用MCS+-SIMS深度剖面仪分析了氧化膜的组成和分布。用光学显微镜、扫描电子显微镜和X射线衍射仪对腐蚀产物进行了表征。结果表明，从保护性的富铬氧化物到非保护性的混合氧化膜的转变是由H2O(G)/O-2比而不是H2O(G)的绝对水平决定的。示踪研究的结果结合现场气体变化实验的数据清楚地表明，在普遍的条件下，水蒸气分子的渗透触发了强化氧化，并维持了在高H2O(G)/O-2比的大气中形成的保护性较差的富Fe氧化膜的高生长速度。如果假设氧化膜内外表面的氧和水蒸气分子的竞争吸附以及在瞬时氧化过程中形成挥发性氢氧化铁，则可以解释实验观察到的结垢增长。在低H2O(G)/O-2-比的气氛中，抑制了非保护性富铁氧化膜的形成，促进了氧化膜的愈合。(C)2006爱思唯尔有限公司。保留所有权利。
The short term (similar to 100 h) oxidation behaviour of the 9%Cr steel P91 was studied at 650 degrees C in N-2-O-2-H2O gas mixtures containing a relatively low oxygen level of 1%. The oxidation kinetics were measured thermogravimetrically and the oxide scale growth mechanisms were studied using (H2O)-O-18-tracer with subsequent analyses of oxide scale composition and tracer distribution by MCs+-SIMS depth profiling. The corrosion products were additionally characterised by light optical microscopy, SEM-EDX and XRD. It was found that the transition from protective, Cr-rich oxide formation into non-protective mixed oxide scales is governed by the ratio H2O(g)/O-2 ratio rather than the absolute level of H2O(g). The results of the tracer studies in combination with the data obtained from experiments involving in situ gas changes clearly illustrated that under the prevailing conditions the penetration of water vapour molecules triggers the enhanced oxidation and sustains the high growth rates of the poorly protective Fe-rich oxide scale formed in atmospheres with high H2O(g)/O-2 ratios. The experimental observations can be explained if one assumes the scale growth to be governed by a competitive adsorption of oxygen and water vapour molecules on external and internal surfaces of the oxide scales in combination with the formation of a volatile Fe-hydroxide during transient oxidation. The formation of the non-protective Fe-rich oxide scales is suppressed in atmospheres with low H2O(g)/O-2-ratios, and the healing of any such scale is promoted. (c) 2006 Elsevier Ltd. All rights reserved.