Protective and non-protective scale formation of NiCr alloys in water vapour containing high- and low-pO2 gases
Protective and non-protective scale formation of NiCr alloys in water vapour containing high- and low-pO2 gases
复制标题
DOI：
10.1016/j.corsci.2008.03.001
复制
发表时间：
2008-06
影响因子：
8.3
通讯作者：
E. Essuman;G. H. Meier;J. Zurek;M. Hänsel;T. Norby;L. Singheiser;W. Quadakkers
中科院分区：
文献类型：
--
作者：
E. Essuman;G. H. Meier;J. Zurek;M. Hänsel;T. Norby;L. Singheiser;W. Quadakkers
研究了Cr含量为10、20和25 wt.%的NiCr合金的氧化行为，分别在Ar-O_2、Ar-O_2-H_2 O和Ar-H_2 O混合气体中进行了研究。TG和SEM分析表明，在湿气中形成在Ni-25 Cr上的氧化铬膜与在Ar-O2中形成的氧化铬膜基本上没有不同。对于两种“边界”合金Ni-10 Cr和Ni-20 Cr，向Ar-O2中添加水蒸气阻碍了保护性氧化铬氧化皮的形成，特别是对于Ni-10 Cr，与干燥气体中的暴露相比，导致氧化皮生长速率显著增加。与文献中描述的具有10- 20%的中间Cr含量的“边界”FeCr合金的许多观察结果不同，相应的NiCr合金在Ar-H2O中显示出比在Ar-O2-H2O中更小的非保护性垢形成趋势。这是由于NiO的生长速率随着测试气体的pO 2的降低而降低，具有在低pO 2气体（例如Ar-H2O）中促进外部氧化铬垢形成的次级效应。即使合金Cr含量太低而不能形成外部氧化铬皮，与低Cr FeCr合金相比，Ar-H2O中的氧化速率也会相当小，因为NiO在这种低pO 2气体中的生长速率非常慢。
The oxidation behaviour of NiCr alloys with Cr contents of 10, 20 and 25wt.%, respectively, were studied in Ar–O2, Ar–O2–H2O and Ar–H2O mixtures. TG and SEM analysis revealed that the chromia scales formed on Ni–25Cr in the wet gases did not differ substantially from those formed in Ar–O2. For the two “borderline” alloys Ni–10Cr and Ni–20Cr, addition of water vapour to Ar–O2hampered the formation of a protective chromia scale which, especially for Ni–10Cr, resulted in substantially increased scale growth rates compared to exposures in dry gas. Different from numerous observations described in the literature for “borderline” FeCr alloys with intermediate Cr contents of 10–20%, the corresponding NiCr alloys showed in Ar–H2O a smaller tendency for non-protective scale formation than in Ar–O2–H2O. This is caused by the decreasing growth rate of NiO with decreasing pO2of the test gas, with the secondary effect that external chromia scale formation is promoted in low-pO2gases such as Ar–H2O. Even if the alloy Cr content was too low to obtain external chromia scale formation, the oxidation rate in Ar–H2O would, in contrast to low-Cr FeCr alloys, be quite small due to the very slow growth rate of NiO in this low-pO2gas.