Oxidation Behaviour of TiAl-Based Intermetallics-Influence of Heat Treatment.

Abstract

The oxidation behaviour of two TiAl - based intermetallic alloys, Ti - 48Al - 2Cr and Ti - 48Al - 2Cr -2nb (at%) were studiedat 800°C in air. Emphasis was placed on the effect of microstructures, obtained by various heat treatments, in a range relevant for practical applications. Ti - 48Al -2Cr-2Nb showed the higher corrosion resistance. Thermal cyclic oxydation experiments showed that localised spallation of the oxide scale formed on Ti-48Al-2Cr initiated after about 175 one- hour cycles leading to significant material loss upon extended exposure. Spallation was limited in the case of Ti - 48Al -2Cr -2Nb. For both materials the growth rate and spallation behaviour of the oxide scale, as well as its composition, structure and morphology showed no major relation to the microstructure of the base material.