Alloy design strategies for promoting protective oxide scale formation

This article discusses general strategies for designing alloys to form prot ective oxide scales. Approaches based on classical alloy-oxidation theories work reasonably well for single-phase alloys. However, high-temperature al loy development has been and will increasingly be based on multiphase micro structures in order to achieve many of the needed, but usually opposing pro perties, such as high-temperature strength and room-temperature toughness. No theoretical-based, well-defined strategies exist for the design of oxida tion-resistant multiphase alloys. Still, key factors are beginning to emerg e, which can provide guidance for promoting the formation of protective sca les on multiphase alloys and for taking advantage of some unique mechanisms that are operative in multiphase alloys but not in single-phase alloys.