Abstract
The alloys based on γ-TiAl have attractive properties as light weight heat-resisting material. The poor oxidation resistance is one of the drawbacks to limit their application. This results from the high growth rate of TiO2 in the scale and the spallation of the oxide scale during cooling. In the present study, the influence of Zr addition on the oxidation behavior of TiAl has been investigated with emphasis on scale adherence. The oxidation behavior of Ti-45Al (in mol %), Ti-45Al-6Nb alloys containing 0 - 0.2% Zr, Ti-Nb and Ti-Zr binary alloys were investigated. The oxide scale was analyzed by conventional methods including X-ray diffractometry, SEM and EPMA. The addition of Nb to TiAl results in a remarkable decrease in mass gain, while the Zr addition to TiAl results in a slight decrease. The Ti-45Al-Nb alloy with Zr shows scale spallation after long term exposure. Concerning the binary alloys, the addition of Zr to Ti more than 20 mol% accelerates the oxide growth significantly. The XRD for Ti-45Al-6Nb-0.2Zr after oxidation shows the formation of Zr oxides and Ti-Zr complex oxides in the scale. The scale spallation observed in this alloy is due to the enrichment of Zr at scale / alloy interface and formation of Zr oxide in the scale.
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