Characterisation of MCrAlY powder before and after thermal coating

MCrAlY (M= Ni, Co) is one of the commonly used alloys for bond coat in aircraft engines or where high temperature tolerance is needed. MCrAlY consists of two major phases among which β-NiAl phase is of most importance as it provides Al for stable α-Al₂O₃ formation. In the present work, we will study the oxidation behaviour of MCrAlY powder in relation to its microstructure before coating, after thermal coating, and after thermal treatment. Characterization will be carried out by scanning electron microscope coupled with an Energy-dispersive X-ray spectroscope (EDS) and an Electron Backscatter Diffraction (EBSD) analyser to determine the shape/size/distribution of phases and their role in oxide layer formation. In addition, identification of oxide formed, and quantification of oxygen content will also be a major part of the study as we want the formation of stable slow growing α-Al₂O₃ instead of fast-growing oxides like NiO, NiAl₂O₄, etc.

This study will establish a relationship between microstructural features and oxidation behaviour and help us find ideal conditions for thermal spray to get the best results i.e. conditions where we can obtain a dense MCrAlY layer while limiting the formation of phases that can have detrimental effects on the overall coat.