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The oxidation properties of Fe-20Cr,Fe-20Cr-0.2Dy and Fe-20Cr-1Dy alloys were studied using gravimetric and electrochemical techniques.The high-temperature oxide films of Dy-doped Fe-20Cr alloys were prepared in air at 900 oC for 24,48 and 100 h,respectively.The electrochemical experiment was performed by a three-electrode electrochemical cell and in 0.1 mol/L Na2SO4 aqueous solution.Proper models were built for describing electrochemical impedance spectroscopy of the different oxide layers and the spectra were interpreted in terms of a two-layer model of the films.The results revealed that the oxide films of Dy-doped Fe-20Cr alloys became compacter than that of undoped alloys and retained their good protective ability for a relatively long time.With increasing content of Dy,the protection of the oxide films slightly decreased.Mott-Schottky curves indicated that all the oxides were n-type semi-conductors,and the Nd value of oxide film on Fe-20Cr was much larger than that of Dy-doped Fe-20Cr alloys.The results of kinetic curves and SEM were in agreement with electro-chemical impedance spectroscopy and Mott-Schottky data.
The oxidation properties of Fe-20Cr, Fe-20Cr-0.2Dy and Fe-20Cr-1Dy alloys were studied using gravimetric and electrochemical techniques. The high-temperature oxide films of Dy-doped Fe-20Cr alloys were prepared in air at 900 oC for 24, 48 and 100 h, respectively. The electrochemical experiment was performed by a three-electrode electrochemical cell and in 0.1 mol / L Na2SO4 aqueous solution. Proper models were built for describing electrochemical impedance spectroscopy of the different oxide layers and the spectra were interpreted in terms of a two-layer model of the films. The results revealed that the oxide films of Dy-doped Fe-20Cr alloys became compacter than that of undoped alloys and retained their good protective ability for a relatively long time. Worth increasing content of Dy, the protection of the oxide films slightly decreased. Mott-Schottky curves indicated that all of the oxides were n-type semi-conductors, and the Nd value of oxide film on Fe-20Cr was much larger than that of Dy-doped Fe -20Cr alloys. The results of kinetic curves and SEM were in agreement with electro-chemical impedance spectroscopy and Mott-Schottky data.