High temperature oxidation resistance of fluorine-treated TiAl alloys: Chemical vs. ion beam fluorination techniques

Surface modification of TiAl alloys by introducing fluorine is known to improve significantly their oxidation behaviour at high temperatures. The effect is based on the preferential reaction of the aluminium with the applied fluorine at the oxide/alloy interface, and is associated with the formation of an adherent and stable protective alumina layer.
Well-defined fluorine profiles beneath the surface of the material can be formed by either fluorine beam line ion implantation (BLI²) or plasma immersion ion implantation (PI3). As an alternative to the implantation-based approach, chemical fluorination techniques such as gas-phase treatment and dipping in F-based solutions have also been investigated in the present work. The fluorine depth profiles have been measured before and after oxidation at 900 °C using non-destructive ion beam analyses (Proton Induced Gamma-ray Emission, Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analysis). The results of this study enable one to optimize the fluorination conditions and to produce surface-modified technical TiAl alloys suitable for industrial applications.