Optimization of reactive-element additions to improve oxidation performance of alumina-forming alloys

It is well-known that the addition of reactive elements (including yttrium, zirconium, lanthanum, cerium, and hafnium) improve the high-temperature oxidation performance of alumina-forming alloys. Less studied are strategies for optimizing these additions for developing a high-performance, wrought FeCrAl alloy with maximum oxidation-limited component life. Results from the literature are summarized regarding potential improvements. One promising strategy is the addition of two reactive elements, such as yttrium and hafnium, which has been effective in commercial and laboratory nickel-based alloys and appears to impart the expected benefits, such as reducing the scale growth rate while minimizing detrimental effects, such as the formation of reactive element-rich oxides in the scale and internal oxidation. Although there are promising data, the long-term studies are not yet complete, and it is difficult to predict if "co-doped" FeCrAl alloys will produce superior oxidation-limited lifetimes in high-temperature environments.