The influence of ternary element addition on the oxidation behaviour of TiAl intermetallic compound in high temperature air

Abstract

A variety of ternary element additions were made to a binary TiAl (Ti-34.5 wt% Al) intermetallic compound and the oxidation behaviour was studied with particular interest in the influences of the ternary elements. As a result of the oxidation tests in air at temperatures between 1073 and 1273 K, the effect of various elements was classified into three groups, i.e. (a) detrimental—Cu, Y, V, Cr and Mn; (b) neutral—Sn, Zr, Hf, Ta, Ni and Co; (c) beneficial—Si, Nb, Mo and W. Their influence was very significant, the difference in the weight gain between the best and the worst alloys being approximately two orders of magnitude. Particularly, the W- and the Mn-modified alloys were approximately 200 and 100 K more resistant than the binary alloy. The mechanism for the improvement by the W and Mo additions may be explained as follows: the elements are enriched on the metal side of the scale/metal interface and may cause the formation of β and/or δ phases in which Al diffusion may be fast and oxygen solubility may be small. This leads to Al-enriched scale formation and/or Al 2O 3 layer formation along the interface.