Incoloy 800H合金在碱性高温高压水中的表面特性研究

Surface property of Incoloy 800H alloy in alkaline high-temperature and high-pressure water

对675℃时效0~10 000 h的Incoloy 800H合金(800H合金)在300℃/10 MPa的碱性高温高压水化学环境中的腐蚀电化学行为和氧化膜显微特征进行了系统研究。通过腐蚀电化学测试、长期浸泡、扫描电镜/透射电镜观察、拉曼光谱/快速傅里叶变化分析等方法,掌握了800H合金腐蚀电化学行为、表面膜形态成分特征随时效时间的变化规律。研究结果表明:时效处理可使800H合金传热管在高温高压水中的开路电位和自腐蚀电位Ecorr小幅升高,但时效时间延长对电化学行为影响不显著;800H合金在高温高压水中呈现钝化过钝化转变,生成的氧化膜呈多层结构,最外层为弥散分布的大颗粒氧化物,组成为Fe2O3或NiFe2O4;中间层为较为致密的小尺寸氧化物,多为NiFe2O4或FeCr2O4;内层则是致密且连续的氧化物,为含Cr和少量Fe的非晶或纳米晶氧化物。800H合金在300℃/10 MPa的碱性高温高压水中具有较好的抗腐蚀性和表面稳定性。

The high-temperature and high-pressure(300 ℃/10 MPa) corrosion electrochemical behavior and oxide film microscopic features of Incoloy 800H alloy aged at 675 ℃ for 0~10 000 h in alkaline environament were investigated systematically. By means of electrochemical test, long-term immersion test, scanning electron microscope/transmission electron microscope observation, Raman spectroscopy/fast Fourier transform analysis and other methods, the electrochemical activity, evolution of oxide film morphology and composition characteristics of the 800H alloy with extension of aging time were systematically studied. The results show that, the value of open circuit potential and self-corrosion potential Ecorr of the 800H alloy in high-temperature and high-pressure water can be slightly increased by aging treatment, but the effect of aging time extension on the electrochemical behavior was not significant. A passive to trans-passive process was depicted. The oxide film of the 800H alloy formed in hightemperature and high-pressure water had a multilayer structure: the most outer layer was the dispersed large particle oxides composed of Fe2O3or NiFe2O4;the middle layer was relatively compact small size oxides, mostly NiFe2O4or FeCr2O4;while the inner layer was dense and continuous oxides, amorphous or nanocrystalline oxide containing Cr and a small amount of Fe. The 800H alloy has good corrosion resistance and surface stability in alkaline high temperature and high pressure water of 300 ℃/10 MPa.