2006 Volume 55 Issue 6 Pages 252-258
The high-temperature oxidation behavior of intermetallic compound TiAl was investigated in oxygen containing trace amounts of halide vapor as NaCl, NaBr or NaF at 1323 K. Mass gain due to oxidation for the TiAl specimen was large in pure oxygen without any halide vapors. In this case, a thick scale consisting mostly of TiO2 was formed on the specimen. In the oxygen containing trace amounts of halide vapor, on the contrary, a small mass gain was observed, not depending on the kind of halide. The result corresponded to the formation of a thin scale consisting of α-Al2O3. Consequently, it was found that a protective alumina scale was preferentially formed on the TiAl in the oxygen containing trace amounts of halide vapor, leading to an improvement in the oxidation resistance of the TiAl in this atmosphere. The reason for the preferential formation of alumina scale was discussed from the standpoint of thermodynamics. A model for the alumina scale formation was proposed that it was caused by a repetition of the halogenating of aluminum at the scale/substrate interface and the oxidation of the aluminum halide in the scale.