Cyclic oxidation behaviour of rare earth oxide coated Fe–20Cr alloys

Abstract

The use of rare earths (REs) to increase high temperature oxidation resistance of chromium dioxide and alumina forming alloys is well known. The REs can be added as elements (or oxides) to the alloys or applied as an oxide coating to the alloy surface. The sol gel technique is very efficient to apply fine oxide particle coatings. The influence of various RE oxide gels such as La₂O₃, CeO₂, Pr₂O₃, Nd₂O₃, Sm₂O₃, Gd₂O₃, Dy₂O₃, Y₂O₃, Er₂O₃ and Yb₂O₃ on cyclic oxidation behaviour (RT-900°C) of Fe–20Cr alloy has been studied. The morphology and coverage of the RE oxide gels varied with the type of RE. The cyclic oxidation resistance increases with increase in time at temperature required to reach a specific chromium dioxide layer thickness and this is influenced by RE ion radius and characteristics of the RE oxide coating such as morphology, stability, coverage, resistance to thermal stresses and consequently adhesion.