研究了P92钢在500~600℃/25 MPa超临界水中的腐蚀行为。用X射线衍射(XRD)和扫描电镜-电子能谱(SEM-EDX)分析了氧化膜微观组织,计算了试样在腐蚀过程中的吸氧量,分析了P92钢在超临界水中的腐蚀动力学规律。结果表明:氧化膜为双层结构,外层氧化膜为Fe3O4相,内层氧化膜为Fe3O4和FeCr2O4相,在接近氧化膜区域的基体内存在一个内氧化区。表面氧化膜中存在许多小孔,小孔数量随着腐蚀时间增加而减少。在生长过程中,氧化膜增重与厚度成线性关系,氧化膜平均密度相对为常数。氧化动力学遵循立方规律,温度对腐蚀速率影响大,600℃的腐蚀速率约为500℃和550℃腐蚀速率的3倍。P92在超临界水中的腐蚀仅表现为氧的吸收,而没有金属溶解。
The oxidation behavior of steel P92 exposed to supercritical water(SCW) at 500 ℃ to 600 ℃ and 25 MPa for 1000 h was investigated by means of gravimetry,SEM,EDX and XRD.The oxide scale was composed of an outer magnetite(Fe3O4) layer and an inner magnetite/spinel-mixed(Fe3O4/FeCr2O4) layer.The initial oxide scale was porous,and the pores decreased with the increase of exposure time.The oxidation rates followed the parabolic law,and increased obviously with the increase of test temperature.There were only oxidation(oxide formation) occurred under the SCW condition,without metal dissolution.