Growth mechanisms of oxide scales on ODS alloys in the temperature range 1000–1100°C

Abstract

AbstractAfter a short overview of the production, microstructure and mechanical properties of nickel‐ and iron‐based Oxide Dispersion Strengthened (ODS) alloys, the oxidation properties of this class of materials is extensively discussed. The excellent oxidation resistance of ODS alloys is illustrated by comparing their behaviour with conventional chromia and alumina forming wrought alloys of the same base composition.ODS alloys exhibit improved scale adherence, decreased oxide growth rates, enhanced selective oxidation and decreased oxide grain size compared to corresponding non‐ODS alloys. It is shown, that these experimental observations can be explained by a change in oxide growth mechanism. The presence of the oxide dispersion reduces cation diffusion in the scale, causing the oxides on the ODS alloys to grow mainly by oxygen grain boundary transport. As oxide grain size increases with time, the oxide growth kinetics obey a sub‐parabolic time dependence especially in the case of the alumina forming iron‐based ODS alloy.