Abstract
The oxidation behaviors of iron and aluminium alloys containing up to 13.65% of aluminium in carbon dioxide gas at the temperature of 500°∼900°C under a pressure of 10 kg/cm2 were studied. The results of experiments were summerized as follows:
(1) The alloys showed a better oxidation resistance with increase in aluminium content at the testing temperature of 500°C. However, at 600°C, the oxidation rate increased, especially for the alloys containing up to 10% aluminium.
(2) This phenomenon is attributed to internal oxidation of aluminium observed in the alloys containing 8.26∼10.46% aluminium.
(3) The internal oxidation of the alloys containing more than above 8% aluminium was not observed at 700°C, and hence the oxidation rate was slower than at 600°C. At 800°C, the oxidation rate further decreased as compared with that at 700°C, but the rate again increased at 900°C.
(4) The oxide film of the alloys containing more than 8.26% aluminium tested at 600°C comprised Fe3O4 and FeO, but the co-existence of Fe3O4 and α-Fe2O3 was found at 700°C, and only the formation of α-Fe2O3 was detected at 800°C. At 900°C α-Al2O3 was observed together with FeO·Al2O3. These changes in the composition of surface oxide films could well explain the effect of testing temperatures on the oxidation rate of the alloys mentioned above.
(5) The creep resistance of iron-aluminium alloys decreased with the concentration of aluminium.
