High-Temperature Oxidation of Intermetallic Compounds of Ti-Al System

Abstract

The resistance to oxidation of Ti-Al Intermetallic compounds (Ti-34% Al and Ti-37% Al) at high temperature under atmospheric oxygen was investigated by continuous (heating for 108 or 180ks) and cyclic oxidation (heating and cooling were repeated) tests. Prior to the oxidation tests, the structures of matrices were controlled by heat treatment and/or isothermal forging. Since the delamination between oxide film and matrix developed on cooling, the oxidation rates of Ti-34Al and Ti-37Al under the cyclic oxidation were faster than those of the continuous oxidation. Under the cyclic oxidation, the oxidation resistance of the Ti-37Al was superior to that of Ti-34Al. The grain size of single phase Intermetallic compounds (Ti-37Al) becomes smaller by forging, but it resulted in the degradation of oxidation resistance. In the case of Ti-37Al, Ti₃Al phase was produced at the interface of matrix and oxide scales. The outer layer of oxide scale on matrices consisted of TiO₂, but the inner layer the mixtures of TiO₂ and Al₂O₃.