Studies concerning the effect of nitrogen on the oxidation behavior of TiAl-based intermetallics at 900°C |
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Authors: | N. Zheng W. J. Quadakkers A. Gil H. Nickel |
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Affiliation: | (1) Research Centre Jülich GmbH, Institute for Materials in Energy Systems, 52425 Jülich, Germany;(2) Academy of Mining and Metallurgy, Krakow, Poland |
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Abstract: | The oxidation behavior of the titanium aluminides Ti-50Al and Ti-48Al-5Nb has been investigated in Ar+20%O2 and in air at 900°C. Thermogravimetric studies in combination with structural analyses using optical metallography, SEM/EDX and X-ray diffraction show a marked influence of nitrogen on the composition and growth rate of the oxide scales. For a more detailed study concerning the effect of nitrogen on the scale-growth kinetics, thermogravimetrical analyses were carried out during which the gas atmosphere was changed from air to Ar–O2, and vice versa, without intermediate cooling of the specimen. The results show, that nitrogen adversely affects the formation of the initially formed alumina scale and that it enhances the growth rate of the rapidly growing Ti-rich oxide. This effect was observed in both alloys investigated, although the thermogravimetric results at first sight indicated an opposite effect for the Nb-containing alloy. This apparent contradiction is caused by internal oxidation which occurs in this alloy during exposure in Ar–O2. |
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Keywords: | TiAl intermetallics high-temperature oxidation Nb additions Al2O3 scales |
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