Improvement of Oxidation-Resistance of γ-TiAl Alloy by High Temperature Nb and Al Ion Implantation

Abstract

The Nb and Al ion implantation on a γ-TiAl based alloy of Ti-48Al-1.3Fe-1.1V-0.3B (at%) at different implantation temperatures of room temperature, 973 and 1173K were performed respectively, with the same dose of 3.0 × 10 21 ions/m 2 and the acceleration voltage of 50 kV. The influence of implantation temperature upon the element distribution in the modification layer and the isothermal oxidation behavior of Ti-48Al-1.3Fe-1.1V-0.3B (at%) at 1173 K for 349.2 ks in air were investigated. It is found that the thickness of the modification layer is significantly increased when the implantation temperature increased to 1173 K in the case of Nb implantation. As Al implantation temperature is raised, Al 2 O 3 is formed and the concentration of Al and Ti in the modification layer is strongly changed. The oxidation resistance of Nb and Al implanted alloys is enhanced as the implantation temperature increased and especially 1173 K Nb implanted alloy shows the best result. The improvement of the oxidation resistance of Nb implanted alloy is attributed to the outward diffusion of Al resulting in the formation of Al 2 O 3 in the oxidation scale and this chemical effect of Nb doping can be further enhanced by high temperature implantation. The formation of Al 2 O 3 in the modification layer during the process of high temperature Al implantation is the main reason for the lower mass gain of high temperature Al implanted alloy. In addition, the reduction of the lattice defect and the stability enhancement of the doping element stayed in modification layer of high temperature implanted alloy are also responsible for the improvement of the oxidation resistance.