ABSTRACT

The oxides formed on T12 ferritic steel surface after exposure to 560 °C/25 MPa supercritical water with dissolved oxygen contents of 300 ppb was characterised by various techniques. It was found that the weight gain and thickness of the oxide scale increase with the increasing exposure time and the oxidation kinetics of T12 followed with parabolic law. The Cr content at the outermost layer increases while the Cr content at the inner/outer layer interface decreases with the increasing of exposure time. The Cr-rich haematite layer oxide was observed on the specimen surface when the test duration extended to 1000 h. The mechanism for the formation of the Cr-rich haematite layer was proposed based on the Cr can diffuse outward through the magnetite layer by short-circuits of the oxide layer and reach the magnetite/haematite interface.

摘要

T12 铁素体钢在暴露于 560 °C/25 MPa 的超临界水中后形成的氧化物，溶解氧含量为 300 ppb，通过各种技术进行表征。发现随着暴露时间的增加，氧化皮的增重和厚度增加，T12的氧化动力学遵循抛物线规律。随着暴露时间的增加，最外层的Cr含量增加，而内/外层界面的Cr含量减少。当试验时间延长至 1000 h 时，在试样表面观察到富铬赤铁矿层氧化物。提出了富铬赤铁矿层的形成机制，基于铬可以通过氧化层的短路通过磁铁矿层向外扩散并到达磁铁矿/赤铁矿界面。