Influence of additional elements on the oxidation behaviour of TiAl

Abstract

The influence of alloying additions on the high-temperature oxidation behaviour of TiAl and materials based on it is critically reviewed in the light of currently proposed mechanisms, i.e. the valence-control rule, Wagner's scaling model and the formation of a barrier layer in the scale. In addition, our newly obtained results are presented, where additions of 0·2 Zr and 0·2 Hf and Nb-ion implantation are dealt with. All the treatments resulted in the formation of highly protective alumina scales which were sound even under thermal cycling conditions. Modification of the initially formed alumina scale is proposed as a fourth mechanism on the basis of our results. Fundamental knowledge on the oxidation of TiAl is also provided for a better understanding.