Fe-10Cr-0.5Al合金の高温酸化

Abstract

A study has been made on the oxidation behaviour of Fe-10Cr alloys with and without Al addition (0.5 mass%) in wet as well as dry oxygen of the atmospheric pressure at temperatures between 1073 and 1173 K. Aluminum addition has increased the protection above 1173 K, below which an effect apparently reversed has been observed within the limit of the test period, i.e., ∼160 ks (∼45 h). The mass gain of the Fe-Cr alloy has been less in the wet than in the dry atmosphere below 1123 K. The Fe-Cr-Al alloy, on the other hand, has not shown such an anomaly under any condition tested. This contrast is not intrinsic one, because the average thickness of the scale on the Fe-Cr-Al alloy in the wet oxygen has not been more than in the dry condition. The excess mass gain in the wet oxygen has been due to the excess in internal oxidation of Al. Further, in the Fe-Cr-Al alloy, two types of scales have been formed at the same time, i.e., a scale composed of outer (Fe, Cr)2O3 layer and inner layer of Al oxide, and the one composed of the internal oxidation zone of Al oxide particles in addition to the outer (Fe, Cr)2O3 layer. The formation of the inner layer, however, has been largely depressed and the internal oxidation zone has been slightly more developed in the wet oxygen.