The improvement of the oxidation resistance of TiAl alloys by fluorine plasma-based ion implantation

Plasma-based ion implantation (PBII) with fluorine ions has been applied for improvement of the oxidation behavior of TiAl alloys. The plasma was produced from Ar-5 vol.%F2 mixed gas with a RF power supplier. 15–30 keV fluorine ions were implanted into Ti50Al (at.%) alloys for 1 h. The oxidation behavior of TiAl alloys was then investigated in air at 850 °C. XPS measurements revealed that prior to oxidation, fluorine ions were located in a very shallow surface region with a peak concentration, and reacted mainly with aluminum to form aluminum fluoride. TiAl treated by fluorine PBII showed a very low oxidation rate, and a protective continuous Al2O3 scale formed on the surface. The beneficial effect of fluorine on oxidation resistance of TiAl was due to that the preferentially formed volatile aluminum fluoride attributed to formation of the continuous Al2O3 scale. Fluorine PBII treatment proves to be a promising surface modification method for improving the oxidation resistance of TiAl alloys.