Oxidation Behavior of Gamma-Titanium Aluminide Alloys

Abstract

ABSTRACTThe oxidation behavior of a number of gamma-TiAl alloys with ternary additions has been studied for extended periods during rapid thermal cycling to temperatures of up to 1000°C in flowing air. Under these conditions, binary alloys, such as Ti-48a/oAl and Ti-52a/oAl form flaking scales with sub-scale embrittlement, although the initial oxidation rate decreases with increasing aluminum content. Ternary Ti-Al-Cr and Ti-Al-Ta alloys with up to 4 a/o Cr or Ta also show a tendency to form spalling scales at these temperatures. On the other hand, the addition of niobium or tungsten results in a dramatic improvement in oxidation resistance at 850 °C, although at 1000°C even these alloys begin to spall after an induction period of several hundred hours.