The oxidation behavior of Fe-18Cr-3Al alloys containing 0.015-0.12% carbon and 0-1.0% titanium has been investigated in air at 1000°C and 1200°C.
At 1200°C carbon and titanium contents have remarkable effects on the oxidation resistance of Fe-Cr-Al alloys, but little effect at 1000°C. Weight gain increases and the formation of unusual oxide scales is accelerated, with increasing carbon content. Though it increases weight gain, the addition of titanium has a tendancy to prevent exfoliation of scales by formation of titanium oxide in scales, and consequently suppresses unusual oxidation.
Stable oxidation is achieved by continuous formation of α-Al2O3, a small amount of TiO2, and Al-Ti oxide. An appearance of iron oxides causes unusual oxidation. The excellent oxidation resistance of Fe-18Cr-3Al alloy is obtained with a carbon content less than 0.03% and titanium content of 0.2 to 0.4%.
