Analytical study of the evolution of alumina scales formed on an ODS alloy

Abstract

An original deflection technique, in association with TEM observations, allowed study of the transformation of metastable alumina phases to α phase. This transformation is mainly characterised by a 14% volume decrease. Deflection experiments were performed on PM 2000 after pre-oxidation, in order to create a 3 µm alumina scale, and subsequent mechanical oxide removal of one large sample face. This technique allowed evaluation of the kinetics of transformation. The microstructural and chemical evolutions of the oxide, the interface (morphology, segregation) and the alloy (aluminium depletion, oxide dispersion) were characterised using TEM analyses and thermogravimetric measurements were done in the same conditions as the deflection tests to determine the oxidation rate constants