ABSTRACT
Protection against oxidation in aluminides and aluminide matrix composites is expected to be due to the formation of alumina scale. Of course, the thermodynamic stability of the oxide scale, along with the strength of its adhesion to the underlying alloy substrate, needs to be considered. The difficulty in formation of protective Al2O3 scale arises because of the competitive oxidation of other alloy constituents, which leads to formation of multiple oxide phases. As a result, internal growth stresses are generated. The scale continuity is interrupted due to spallation or loss of volatile oxidation products. The products of oxidation are also found to vary with temperature. The mechanisms of oxide-scale formation and spallation, as well as the factors influencing such phenomena and also the issues of scale adherence to the alloy underneath, are discussed in this chapter.
