Effects of C, Nb and C+Nb combined ion implantation on the oxidation resistance of γ-TiAl based alloy

Abstract

The isothermal oxidation behavior of Ti–48Al–1.3Fe–1.1V–0.3B (at.%) implanted with C, Nb or C+Nb was investigated at 1173 K for 349.2 ks in air. Dose was 3.0×10 21 ions per m 2 and the acceleration voltage was 50 kV for each element. The purpose of this study is to improve the high-temperature oxidation resistance of the alloy by suitable implantation process and clarify the effects of C, Nb and their interaction on the formation of the oxide scale. Thermobalance, auger electron spectroscopy (AES) and scanning electron microscopy (SEM) were used to characterize the oxidation behavior and the scale structure. It was found that the C implantation is harmful to the long-term oxidation resistance, the Nb implantation significantly decreases the oxidation rate, and the C+Nb implantation can further improve the beneficial effect of the Nb implanted alloy and thus gives the best oxidation resistance. It was also found that for the C implantation, the C rich layer can act as a barrier to the inward diffusion of O in the early stage of the oxidation, but this effect will disappear after oxidation for about 3.6 ks due to the fast consumption of C. The presence of Nb can promote the formation of an Al enriched layer in the external scale. The co-existence of Nb and C would enhance their respective stability remained in the external scale or substrate with high peak concentration and thus prolong and intensify their respective beneficial effects. The significant improvement of the oxidation resistance of the C+Nb combined implantation is attributed to the above respective C and Nb beneficial effect and their interaction during the oxidation.