Effect of coating on oxidation of impure (C,Mn) iron at 700°c: yttrium–impurity interactions

Abstract

A study of the interactions between carbon and manganese impurities and yttrium has been performed during the oxidation of iron base specimens under an oxygen partial pressure of 0·04 Pa and at a temperature of 700°C. It was found that yttrium coated specimens always exhibit better oxidation behaviour than uncoated specimens. For a manganese containing alloy (Fe–0·2Mn), the protective effect of yttrium is attributed to the formation of a YMnO₃ subscale at the oxide-metal interface. On Fe and Fe–0·054C substrates the beneficial effect is attributed to the formation of Fe₂ YO₄ (which is more protective than YMnO₃ ). The best improvement is obtained with coated Fe–0·18Mn–0·041C alloys as a result of the formation of a YMnO₃ subscale at the scale-alloy interface, and because the yttrium coating hinders carbon segregation at the oxide-alloy interface, thus producing better scale adhesion.