Oxidation of MCrAlY coatings on Ni-based superalloys

Abstract

This research is concerned with advanced characterisation of thermally grown oxides (TGO) on MCrAlY bond coats with differing chemical compositions. The purpose of the research is to develop an improved understanding of TGO growth and related failure mechanisms aimed at enhancing the lifetime prediction methods for coated blade systems used in industrial power generation. It is shown that a continuous alumina layer forms on a NiCoCrAlY bond coat comprising primarily of the β and γ phases, whereas a two layer oxide, rich in both chromium and aluminium respectively, is formed on a NiCrAlY bond coat which contains the γ′ and β phases. In both cases, the grain structures within the TGO are extremely fine, and additional complex precipitates are found only within the alumina.