The Change in Growth Mechanism of Scales due to Reactive Elements

摘要

An analysis of the effect of reactive elements, or their oxides, upon high temperature-oxidation behavior of chromia-forming alloys is presented in this note. The change in mechanism for the growth of "pure" chromia, cation motion in the scale, to that formed on alloys containing the reactive elements, anion motion in the scale, is attributed to the fact that almost all reactive-element oxides are, on the basis of ion motion, anionic conductors. Thus, the reactive-element oxide present as an adsorbed layer at the chromia grain interfaces as well as fine particles residing at these interfaces restricts cation motion and imposes anion diffusion along these primary paths of scale growth. The effect of scale adherence is not addressed.