超临界二氧化碳环境下耐热钢T91腐蚀行为机理研究

Corrosion behavior and mechanism of heat-resistant steel T91 in supercritical carbon dioxide environment

超临界二氧化碳循环发电系统具有效率高、设备体积小和用水量小等优点,其应用前景广阔,该系统高温部件结构材料的抗腐蚀性能是确保系统长周期安全高效运行的决定因素之一。本文在超临界二氧化碳环境下开展高温部件典型材料耐热钢T91的腐蚀机理试验,利用X射线衍射仪、扫描电子显微镜和辉光放电光谱仪分析耐热钢T91表面腐蚀产物类型、成分及其分布。结果发现:在试验条件下超临界二氧化碳环境中,耐热钢T91腐蚀动力学规律符合抛物线型腐蚀规律,说明腐蚀过程受离子扩散控制;耐热钢T91腐蚀的主要类型为全面腐蚀,并且腐蚀产物表面出现C富集现象;耐热钢T91表面的腐蚀产物从气固界面到基体依次为Fe3O4、(Fe,Cr)3O4与碳化物和弥散于基体的碳化物;超临界二氧化碳环境中腐蚀产物(Fe,Cr)3O4层与耐热钢T91基体出现渗碳现象,说明腐蚀过程中发生氧化和碳化反应,研究结果丰富了超临界二氧化碳腐蚀中C元素的演变规律。

The supercritical carbon dioxide cycle power generation system has the advantages of high efficiency,small space occupation and huge water saving,which has broad application prospects.To ensure the long-term safe and efficient operation of this system,the corrosion resistance of high-temperature structural materials is one of the decisive factors.In the experiment,the corrosion behavior and mechanism of the heat-resistant steel T91 was studied on a supercritical carbon dioxide corrosion platform.X-ray diffractometer,scanning electron microscopy and glow discharge spectrometer were used to analyze the type,compositions and distribution of the corrosion products on surface of the heat-resistant steel.The results showed that,the corrosion law of the heat-resistant steel T91 in supercritical carbon dioxide environment followed a parabolic corrosion law,indicating that the corrosion process was controlled by the ion diffusion.The main type of corrosion of heat-resistant steel T91 was general corrosion,and the C-rich products were detected on surface of the corrosion products on T91.The corrosion products on surface of the heat-resistant steel T91 were Fe3O4,(Fe,Cr)3O4 and carbides,and carbides dispersed in the matrix from the gas-solid interface to the substrate.In the supercritical carbon dioxide environment,carburization phenomenon occurred on the(Fe,Cr)3O4 layer and the substrate,indicating that oxidation and carbonation reaction occurred during the corrosion process.The results enriched the evolution law of C element in supercritical carbon dioxide corrosion.