The corrosion of M38 and M38 with small additions of Y and Ce has been studied at the temperature range of 700-900 ℃. Mixtures of SO_2 and O_2 in the ratios of 2:1 and 1:4 were used. Equilibrium Pso_3 was obtained by positioning a Pt-10%Rh net catalyst at the exit of gases in-let tube. The corrosion kinetics was studied by a self-made apparatus using the non-continuous method. In all cases the curves of weight-gain versus time are analogous to the parabolic law. Surface morphology of the corroded specimens was examined using a scanning electron microscope. The element distributions were studied by a electron probe and the corrosion products analysed by x-ray diffraction. It was found that the product of M38 consists of three layers: a innerlayer of sulside, a outerlayer of several kinds of oxides and a interlayer of sulfides and oxides mixture. The preferential oxidation of Cr, Ti, Al, Ta and the small additions of Y and Ce were benificial to the corrosion of M38 in the mixed environments. In this paper, a model of sulfidation and oxidation was proposed and the effects of Cr, Ti, Al, Ta and Y, Ce were discussed.
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