Influence of implantation of a few metal ions on the oxidation behaviour of TiAl at high temperatures

TiAl coupon specimens were implanted with Ar, Al, Si, Cr and Nb ions of a dose of 10/sup 21/ ions/spl middot/m/sup -2/ at an acceleration voltage of 50 keV. Varying doses between 10/sup 20/ and 10/sup 18/ ions m/sup -2/ were also examined for Nb implantation. In addition, implantation of Zr was also examined with doses of 10/sup 20/ and 10/sup 19/ ions/spl middot/m/sup -2/ and acceleration voltages of 50 and 180 keV. The oxidation resistance was assessed by cyclic oxidation tests with temperature varying between room temperature and 1200 K in a flow of purified oxygen under atmospheric pressure. The holding time at temperature was 72 ks (20 h) or 3.6 ks (1 h). Conventional metallographic examinations were performed for implanted specimens and oxidised specimens using glancing angle X-ray diffractometry, AES, SIMS, SEM and EDS. The implantation of Ar ions significantly enhances the oxidation. Al and Si suppress the oxidation during the initial period. This effect is much larger for the implantation of Si. The implantation of Cr does not improve the oxidation resistance. The implantation of Nb of the highest dose results in the excellent oxidation resistance by forming very protective Al/sub 2/O/sub 3/ scales, The oxide scale does not spall for at least up to 300 cycles (300 h). This effect decreases when the dose is decreased. The implantation of Zr improves the oxidation resistance to some degree.