Yb/Dy掺杂改性Fe-Cr合金热生长氧化膜的电化学阻抗谱研究

ELECTROCHEMICAL IMPEDANCE MEASUREMENT ON THERMAL GROWN OXIDE FILMS OF RARE EARTH ELEMENT Yb/Dy-MODIFIED Fe-Cr ALLOYS

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 effect of 0.2 mass%Yb/Dy additives on the oxidation resistance of Fe-20Cr alloy at 900℃in air was studied,and EIS was used to investigate the electrical conductivity of oxide scales formed on the alloys at 900℃.Experimental results indicated that the addition of Yb and Dy to Fe-20Cr promoted the formation of a Crrich oxide scale,increased the adhesion of oxide scales,and thus improved its oxidation resistance,with a better effectiveness observed for the element Dy.Electrochemical impedance spectra for the oxidized Fe-20Cr-0.2Dy in neutral Na_2SO_4 solution bubbled with N_2 were composed of double capacitive loops,suggesting a two-layer structure of the films,however,which was not obviously observed from EIS of the oxidized Fe-20Cr and Fe- 20Cr-0.2Yb.The lowest electrical conductivity was observed for the scales formed on Fe-20Cr-0.2Dy,indicating a better oxidation resistance,as confirmed by kinetic measurements.The capacitance and resistance obtained can be related to the thickness and defectiveness of oxide scales,so electrochemical impedance spectroscopy was a proper investigating method for the oxidation and corrosion of metal and the results of other analytical techniques were in agreement with the EIS data.