Hideo Ike1 and Hirobumi Okabe1
Osaka Prefectural Industrial Research Institute, Osaka
The oxidation of Fe-Cr-0.3%Al alloys containing 15∼28%Cr in atmospheric dry oxygen at 1173∼1473 K has been studied by thermogravimetric methods, metallography and scanning electron microscopy. Effects of Al on the oxidation resistance decrease with an increase in the Cr content of the alloys. Spallation of the oxide scales after cooling can be completely avoided by the addition of Al below 1273 K. Above 1373 K, however, the effect of Al decreases as the Cr content in the alloy increases. Uniform single-layered scales of (Fe,Cr)2O3 rich in Cr are produced. All of the alloys tested with Al additions form internal oxidation zones of α -Al2O3. A brief discussion has been given on the optimal amount of Al within a small range of addition. The apparent activation energies are within a range from 205 to 223 kJ/mol. The durations which obey the parabolic rate law are longer for the alloys without Al addition below 1273 K. Finally, the spalling behaviour of the scales has been discussed in some detail.
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