Oxidation protection of TiAl alloys by plasma-based ion implantation of fluorine

Plasma-based ion implantation (PBII) of fluorine is a promising technique for enhancing the high-temperature oxidation resistance of γ-TiAl alloys. This talk is in two parts. The first part summarizes our recent progress in utilizing the PBII process. Experimental results are presented that give an insight into the behavior of the ion-implanted fluorine and its role in the formation of a protective alumina scale under conditions of both isothermal and thermal cyclic oxidation at temperatures in the range of 720° to 1050°C. Although PBII of F is not yet a commercially feasible proposition, shown are examples that give a flavor of potential applications (turbine blades and turbochargers). The second part of the talk deals with enhancing the environmental durability of Ti and some low-Al content (typically < 10 at.%) Ti-base alloys at elevated temperatures by forming a protective coating on the alloy surface. The coating is accomplished through a three-step process, namely co-deposition of Ti and Al by magnetron sputtering onto a substrate material followed by vacuum annealing to form a layer of γ-TiAl, which is finally treated by PIII of F to provide the necessary conditions for triggering the halogen effect. Shown are analysis data detailing the microstructure and the phase formation in the coating material.