Oxidation resistant Ti-Al-Cr alloy for protective coating applications

Ternary Ti-Al-Cr alloys offer excellent oxidation stability at elevated temperatures due to the formation of a continuous alumina surface layer during oxidation in air. We have investigated the oxidation kinetics and surface oxide characteristics of several Ti-Al-Cr compositions. It is shown that alloys containing mainly the τ and Laves phase exhibit superior oxidation stability over a wide range of temperatures (750–1100°C). The best oxidation stability is exhibited by the (Ti0.25Al0.55Cr0.2) alloy containing near 70–75 at. % of τ and 25–30% Laves phases. Further improvement of this alloy's oxidation stability results from synergistic doping by a small amount (01–0.2% atomic) of active metals such as Hf and Y as well as Si (above 1%).