Y-rich oxide distribution in plasma sprayed MCrAlY-coatings studied by SEM with a cathodoluminescence detector and Raman spectroscopy

SEM cathodoluminescence (CL) imaging and Raman spectroscopy were used to study the compound type, distribution and morphology of Y-rich oxide particles in MCrAlY-coatings at various stages of the manufacturing and oxidation exposure. Compared to conventional SEM/EDX, CL allows easy detection of Y-rich oxides at a high, sub-µm resolution with a fast image acquisition. Furthermore, phase analysis of the Y-rich oxide compounds based on the wavelength resolved Raman spectra and in some cases also using CL-spectra is possible. esented results of the cathodoluminescence and Raman spectroscopy studies indicate that the type of the Y-rich oxide phases after heat-treatment can be correlated with the content and/or reservoir of metallic Y in the coating. Hence, these analytical methods have potential to be applied as (non-destructive) quality control methods in the manufacturing of MCrAlY-coatings. The distribution of the Y-rich oxide precipitates formed during manufacturing has been shown to affect the growth rate and mechanical stability of the alumina scales during service. Y-oxide distribution in the MCrAlY-coatings, therefore, represents a factor, which influences the lifetime of overlay and TBC-coatings.