Role of reactive elements in alloy protection

Abstract

Reactive element additions may promote the formation of protective oxide scales on high temperature alloys, and improve long term oxidation resistance by limiting the rate of scale growth and inhibiting scale failure processes. Various modifications to transport properties and mechanical behaviour have been proposed to explain the observed benefits. These mechanisms are reviewed with reference to available experimental evidence. Key steps in enhancing oxidation resistance are probably the provision of reactive element oxide particles for incorporation into a scale and consequent segregation of reactive element ions to high diffusivity pathways and interfaces. Such behaviour is consistent with known variations in protection resulting from changes in reactive element type, concentration, and initial distribution. MST/1055