The Oxidation of Fe-Al Alloys Containing Chromium, Nickel, or Manganese Available to Purchase

A review of recent work into the oxidation characteristics of iron-aluminum alloys containing between 1 and 5 Wt% aluminum is presented, with emphasis on the effect of ternary alloying additions. Those described are chromium (a ferrite stabilizer), nickel, and manganese (both austenite stabilizers), in concentrations of up to 30 to 40 Wt%. While binary iron-aluminum alloys require greater than 7 Wt% aluminum for excellent oxidation resistance at 800 C, it is shown that chromium additions of greater than 5 Wt % enable a protective alumina scale to be established on alloys with as little as 2.5 Wt% aluminum. Nickel and manganese additions are less effective in promoting alumina scales and higher aluminum concentrations are required to maintain similar levels of resistance compared to binary Fe-Al or ternary Fe-Al-Cr alloys. It is shown that it is impossible in either alloy system to develop austenitic alloys that form protective alumina scales. However, highly oxidation resistant ferritic, alumina-forming alloys exist over a wide range of ternary compositions.