Oxidation Protection of Titanium Aluminides and Ni-Base Superalloys at High Temperatures by the Halogen Effect – Principles and Applications
The oxidation protection of TiAl-alloys at temperatures above 750°C can be improved by the fluorine effect. The results of thermodynamical calculations predict a corridor for a positive fluorine effect. Ion implantation of F was performed because of giving the best results. After a high F-loss during heating a thin protective alumina scale acts as a diffusion barrier. The F-depth profiles show a distinct maximum at the metal/oxide interface. The diffusion coefficient of F in TiAl for 900°C was determined. The stability of the F-effect after long oxidation time at 900°C and 1000°C can be explained by the existence of a constant F-amount at the metal/oxide interface ensuring a slow growth of the alumina scale. The fluorine effect was also applied to Ni-base superalloys to improve their high temperature oxidation resistance by forming a dense continuous protective alumina scale.
Toshio Maruyama, Masayuki Yoshiba, Kazuya Kurokawa, Yuuzou Kawahara and Nobuo Otsuka
H. E. Zschau and M. Schütze, "Oxidation Protection of Titanium Aluminides and Ni-Base Superalloys at High Temperatures by the Halogen Effect – Principles and Applications", Materials Science Forum, Vol. 696, pp. 366-371, 2011