Strategy for Applying Microanalytical Techniques

A combination of microanalysis techniques is used to reveal with great precision the composition and microstructure of typical features in engineering materials. In this paper small particles, very thin films, interfaces and their contiguous region are considered. Small silicon nitride particles in an iron matrix produced by nitriding are characterized quantitatively with High Resolution Electron Microscopy (HREM) and Electron Probe Micro Analysis (EPMA) using Wavelength Dispersive X-ray Spectrometry (WDS). Thin aluminium-oxide films grown on aluminium substrates by thermal oxidation at low pressure are investigated with HREM and X-ray Photoelectron Spectroscopy (XPS). Their thickness, composition and degree of crystallinity are established as a function of oxidation temperature and time. At and near the oxide-layer/MCrAlY-coating (M=Ni and/or Co) interface the aluminium and chromium depletion behaviour of the coating material due to high-temperature oxidation is studied with high-resolution Scanning Electron Microscopy (SEM), EPMA and Auger electron spectroscopy (AES). The composition-depth profiles obtained for the coating material are used to determine the composition dependent diffusion coefficients. These properties are crucial for the prediction through computational modelling of the coating material oxidation behaviour and enable the development of new coating materials.