High temperature corrosion of B2 iron aluminides

The high temperature oxidation of two B2-Fe40A1 Iron Aluminides has been studied in isothermal and cyclic conditions in the range 700 degrees C to 1100 degrees C and compared with a FeCrAlY alloy. One of the aluminides was prepared by mechanical alloying with the addition of an Y2O3-dispersion that conferred to it improved mechanical properties. No significative differences in the isothermal oxidation of the aluminides have been observed due to the presence of the Y2O3. Both aluminides presented higher oxidation rates than the FeCrAlY alloy at 758 degrees and 858 degrees C but lower rates at 1118 degrees C. The tests carried out under thermal cycling (100 1-hour cycles: 40 minutes at 900 degrees C plus 20 minutes at room temperature) showed that the FeCrAlY alloy presented a lower weight increase than both Iron aluminides. Scanning electron microscopy observations revealed a similar acicular morphology of the thin oxide layer formed on the aluminides. The oxide grown on the FeCrAlY alloy presented nodule formation. (C) 1998 Elsevier Science Ltd. All rights reserved.