Alloy design strategies for promoting protective oxide scale formation

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