Characterization of Thin Oxide using FIB-SIMS and FIB-TEM Techniques

The use of SIMS for the characterization and study of biomaterial surfaces is fast gaining popularity in the development of bio-functional and bioactive tissue compatible interfaces. The presence of TiO
2
oxide in metallic Ti implants and its ability to promote bioactivity is still unclear. FIB-SIMS (Focused Ion Beam-Secondary Ion Mass Spectrometry) and FIB-TEM (FIB-Transmission Electron Microscopy) techniques represent powerful tools for characterizing the oxide layer. This paper investigates the oxygen transport mechanism of thermal barrier coating systems applied on nickel-base superalloy turbine blades. In this study, a two-stage oxidation experiment is used.
¹⁸
O
2
is used as a tracer during the second stage oxidation on previously oxidized Ni-base superalloys with a layer of bond coat material. The aluminium oxide grown in
¹⁶
O
2
during the first stage oxidation serves as a background oxide. Mass spectra collected by FIB-SIMS reveal the counter mass transportation by inward diffusion of oxygen and outward diffusion of aluminium. New oxide formation during the second stage oxidation under an
¹⁸
O
2
enriched environment is observed at both the gas/oxide interface as well as oxide/superalloy interface. Transmission Electron Microscopy (TEM) can be used to identify the very fine phases developed in both the inter-diffusion zone as well as the thermally grown oxide layer. The use of Focused Ion Beam (FIB) technique allows for selective nano-machining of areas of interest for the production of TEM samples. FIB-SIMS and TEM are carried out to determine the specific phase transformations occurring in the TBC system.