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研究了掺杂0.2 mass%Yb和Dy对Fe-20Cr合金在900℃空气中的氧化性能的影响,应用电化学阻抗技术研究在中性硫酸钠溶液中合金表面氧化膜的电导率,对高温氧化膜的性能进行描述并建立适当的等效模型。结果表明,加入元素Yb和Dy有助于促进合金表面富Cr氧化膜的形成,提高氧化膜的粘附性,从而改善合金的抗氧化性能,其中元素Dy的作用效果比Yb更好。Fe-20Cr和Fe-20Cr-0.2Yb合金表面氧化膜在溶液中的电化学阻抗谱不能看到明显的双容抗弧特性,而Fe-20Cr-0.2Dy的双容抗弧特性明显,表明氧化膜是双层结构,且其表面氧化膜的电导率最小,显示更好的抗氧化性能,这与氧化动力学测量结果一致。通过与其它高温氧化分析方法进行比较,发现对于研究氧化膜的结构特点、孔隙率、缺陷性等电化学阻抗谱有其独特的优势。
The effects of doping 0.2 mass% Yb and Dy on the oxidation performance of Fe-20Cr alloy in air at 900 ℃ were studied. The electrochemical impedance spectroscopy was used to study the conductivity of the oxide film on the alloy surface in neutral sodium sulfate solution, The performance of the membrane is described and an appropriate equivalent model is established. The results show that the addition of Yb and Dy can promote the formation of Cr-rich oxide film on the alloy surface and improve the adhesion of the oxide film, thus improving the oxidation resistance of the alloy. The effect of elemental Dy is better than that of Yb. The electrochemical impedance spectroscopy of Fe-20Cr and Fe-20Cr-0.2Yb alloy oxide films in solution did not show obvious double capacitive arc behavior, but the double capacitive arc behavior of Fe-20Cr-0.2Dy was obvious, indicating that the oxidation The membrane is a bilayer structure, and the conductivity of the oxide film on the surface is minimal, indicating better oxidation resistance, consistent with the oxidation kinetics measurements. Compared with other methods of high temperature oxidation analysis, it is found that electrochemical impedance spectroscopy has unique advantages for the study of structural characteristics, porosity and defects of oxide films.