Oxidation behavior of TiAl protected by Si plus Nb combined ion implantation

The combined ion implantation of Si c Nb at room temperature and at 1173 K with C contamination was employed to improve the oxidation resistance of a gamma -TiAl based alloy [Ti-48Al-1.3Fe-1.1 V-0.3B (at%)]. The implantation was conducted with a dose of 3.0 x 10(21) ions/m(2) and at an accelerate vo ltage of 50 kV for each element. The isothermal oxidation behavior of above treated alloys was tested at 1173 K for 349.2 ks in air. The oxide scales formed by short-term and long-term oxidation were characterized by AES, SEM and XRD. It was found that the alloy implanted with Si + Nb at 1173 K with C contamination shows excellent long-term oxidation resistance in comparis on to that of the room temperature Si;Nb implanted alloy, although the latt er also significantly lowers the oxidation rate of non-implanted alloy. A c ontinuous, compact and thus a protective Al2O3 layer was formed in the scal e of the alloy implanted with Si + Nb at 1173 K with C contamination after long-term oxidation, and this layer contributed to the best oxidation resis tance. It is also indicated that the introduction of Si into Nb modified la yer and, in particularly C in conjunction with Nb and Si in the modified la yer can further effectively favor the formation of the continuous Al2O3 lay er in the scale on alloy during high temperature oxidation. (C) 2001 Elsevi er Science Ltd. All rights reserved.