High-temperature oxidation behavior of TiAl-based alloys fabricated by spark plasma sintering

Alloys of Ti-45Al-8.5Nb-0.2B-0.2W-0.1Y and Ti-47.5Al-2.0V-1.0Cr have been prepared by spark plasma sintering (SPS). Their high-temperature oxidation behavior at 1000 degrees C in air has been investigated. The results indicate that the Ti-45Al-8.5Nb-0.2B-0.2W-0.1Y alloy possesses superior oxidation resistance, which is greatly better than that of Ti-47.5Al-2.0V-1.0Cr alloy under the same condition. The enhanced property is mainly attributable to 8.5 at.% Nb addition. For the Ti-47.5Al-2.5V-1.0Cr alloy, the outer oxide scale is dominated by TiO2 with a small amount of Al2O3, and the inner scale consists of many separate alternating Al2O3/TiO2 layers. By comparison, the inner oxide scale of Ti-45Al-8.5Nb-0.2B-0.2W-0.1Y underneath the outer TiO2-rich layer is composed of TiO2 and a minor amount of TiN. Additionally, Nb is found to be enriched at the interface of the oxide scale and the substrate. The addition of Nb promotes the formation of TiN in the oxide scale and Nb-enriched diffusion layer between the scale and the substrate, which is effective to impede the diffusion of Ti and O ions. (C) 2008 Elsevier B.V. All rights reserved.