7.3. Oxidation and hot corrosion
The high-temperature corrosion behavior of Fe3Al alloys has recently been reviewed by Natesan and Tortorelli [53]. The formation of Al2O3 films provides oxidation resistance; the minimum Al content to form Al2O3 is 16–18 at.% and these films can form even in low pressures of oxygen. Small additions of Cr can reduce the minimum Al content somewhat. The mechanical integrity of the films and their reformation characteristics are critical to adequate behavior at long exposures. When Fe3Al is exposed to sulfur-bearing atmospheres, weight gain is adversely affected by the presence of large quantities of Cr, as shown in Fig. 17 [53]. Note that the binary Fe-12 wt.% Al alloy as well as Fe3Al alloy FA-61 shows no weight gain at 875°C. Apart from Cr, the only other solute which has been studied in detail is Zr, which appears to improve oxide adherence at elevated temperatures