高温炭酸ガス中におけるFe-Al合金の酸化におよぼすCrの影響

Abstract

The mechanical properties and oxidation resistance of Fe-Al-Cr alloys containing 8∼14% aluminium and 5% chromium in carbon dioxide gas at the temperatures of 600°∼900°C under a pressure of 10 kg/cm2 were studied. The results of experiments were summarized as follows:(1) The oxidation of Fe-Al-Cr alloys at the temperatures tested decreased with increasing aluminium content. The oxidation rate of the alloys decreased with time and finally approaches a plateau after 300 hr.(2) The oxidation resistance of Fe-Al alloys could be improved by the addition of more than 5% chromium provided that the content of aluminium is over 8%.(3) The internal oxidation of aluminium observed in the Fe-Al alloys containing 8-10% aluminium was inhibited by the addition of chromium.(4) The oxide formed at the temperature of 700°C was identified by an electron diffraction technique as a mixture of α- Fe2O3 and α-Al2O3, but the formation of α-Al2O3 was prodominant over 800°C.(5) The tensile properties and hardness of Fe-Al alloys at the temperatures of up to 800°C were not affected by the addition of chromium.(6) The ductility of Fe-Al(8%)-Cr(5%) alloy was makedly decreased by heating in carbon dioxide gas, and this phenomenon is attributed to the precipitation of chromium carbide at the grain boundary due to the carburization in high temperature gas.(7) The decrease of creep resistance of Fe-Al alloys with increasing aluminium content could not be improved by the addition of chromium.