Characterization of oxidized Ni-based superalloys by GD-OES

Abstract

In this work, the analysis of various high-temperature materials after oxidation using Glow Discharge Optical Emission Spectrometry (GD-OES) will be presented. The results of depth profiles of four Ni-based superalloys that form different oxide scales after oxidation at high temperatures will be shown. It was determined that GD-OES is a very flexible method allowing for analysis of different types of oxide scales formed on the alloys after operation. This method enables analysis of the oxides varying in chemical composition, as well as thickness (ranging between a few μm up to 150 μm). It will be shown that the GD-OES method is not only suitable for analysis of oxide scales, but also for studying protective coatings on a superalloy substrate, commonly used in the hot sections of gas turbines or jet engines. It was found that the GD-OES technique allows to obtain depth-resolved information with relatively good depth resolution at very thick layers, where other techniques fail due to e.g. sputtering time. The presence of precipitates and laterally inhomogeneous oxides additionally excludes other techniques with high lateral resolution. The results of GD-OES analysis will be confirmed by other analytical techniques, such as light optical microscopy (LOM) and scanning electron microscopy (SEM).