High-temperature oxidation of Ti{sub 3}Al-based titanium aluminides in oxygen
- Indian Inst. of Tech., Kanpur (India). Dept. of Materials and Metallurgical Engineering
The oxidation behavior of Ti-25Al, Ti-24Al-15Nb, and Ti-25Al-11NB (at. pct) titanium aluminides was studied in dry oxygen at atmospheric pressure in the temperature range 1,000 to 1,300 K for 4 to 6 hours by thermogravimetry. The oxidation products were characterized by X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray (EDX) analysis. Although some departures from the parabolic rate law were found, the analysis of data revealed that the parabolic rate law was a more reliable basis for interpretation of results as compared to the empirical power law. Parabolic rate constants (k{sub p}) for Ti-24Al-15Nb and Ti-25Al-11Nb were almost the same at the same temperature. However, k{sub p} values for Ti-25Al were 2 to 8 times larger than niobium-containing alloys except at 1,000 K, where k{sub p} values for all three alloys were approximately the same. The effective activation energy (Q{sub eff}) was 289 kJ/mole for Ti-25Al in the range of 1,000 to 1,300 K, while in the case of Ti-24Al-15Nb and Ti-25Al-11Nb, Q{sub eff} values were 329 and 330 kJ/mole, respectively, in the range of 1,100 to 1,300 K. In general, the scales on Ti-25Al were porous and exhibited significant spallation above 1,100 K. The scales were thinner, compact, and adherent for niobium-containing alloys. The scales formed on these alloys were predominantly composed of TiO{sub 2}, while Al{sub 2}O{sub 3} was also present as a minor constituent. The superior oxidation resistance of the niobium-containing alloys has been attributed to the doping effect of niobium in TiO{sub 2}.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 438562
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 12 Vol. 27; ISSN 1073-5623; ISSN MMTAEB
- Country of Publication:
- United States
- Language:
- English
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