Some Observations on the Effects of Sulfur and Active Elements on the Oxidation of Fe-Cr-Al Alloys

摘要

A very-low-sulfur-content industrial Fe-Cr-Al alloy has been used both as a baseline and as a charge material for laboratory melts with variable sulfur and rare-earth additions. No significant differences in behavior were observed in cyclic oxidation tests on 1-mm-thick coupons at 1100℃, except for an excessive rare-earth content, which led to accelerated scale growth. At 1300℃, alloys without rare-earth additions developed high growth stresses in the oxide, leading to large tensile strains in the substrate. The oxide-metal interface in the low-sulfur (< 2 ppm) material resisted these stresses and the oxide remained adherent. However, as little as 4 ppm S was sufficient to cause considerable spalling. Rare-earth additions markedly reduced growth stresses and eliminated both dimensional instability and spalling.