Oxidation-resistant high temperature alumina-forming alloys

Alloys in the Ti-Al system arc of interest for high temperature systems such as aircraft engines because they have low density and maintain strength at high temperature. However, their resistance to oxidation and interstitial embrittlement is a concern. Those alloys which form alumina scales have excellent resistance to surface re-... 

From Fig. 7-1 it can be seen that after silica forming materials, those materials with the next most protective oxide scale would be alumina formers. Since alumina scales are less sensitive to impurities, AIN and AI4C3 appear, at first glance, to be ideal high temperature oxidation resistant materials. However, the recession rates in this figure are based on those observed for alumina forming metal alloys. Oxidation of both of these ceramic materials results in the formation of gaseous products which can alter the protective qualities of the alumina scale. 

Because of their excellent oxidation resistance, Fe-Cr-Al alloys are commonly used construction materials for components that have to operate at high temperature. The oxidation resistance relies on the formation of slowly growing, well adherent alumina-based surface oxide scales, which form during high temperature exposure. Examples of the application of Fe-Cr-Al alloys are heating element strips or wires, fibre-based domestic and industrial burners, car catalyst carriers, furnace tubes, etc. 

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