Improving the Oxidation Resistance of TiAl-Alloys with Fluorine

The technical TiAl-alloy gamma-MET (Ti-46.5Al-4(Cr, Nb, Ta, B)) was oxidised thermocyclically (24h-cycle-test) at 900 degrees C in wet and dry air. In this paper results of untreated and fluorine treated TiAl-samples are presented. Their oxidation behaviour will be shown. Several methods were used to apply the halogens to the surface, e.g. beamline ion implantation, spraying of or dipping into a halogen containing liquid. A pure protective alumina scale was found, e.g. after treatment with a fluorine containing polymer and thermocyclic oxidation up to 1 year at 900 degrees C in laboratory air. On the other side thick fast growing and non-protective mixed oxide scales were found on the untreated samples.