Investigations on the oxidation behaviour of MAX-phase based Ti₂AlC coatings on γ-TiAl

Abstract

In the field of aerospace and automotive industry the development of light materials with resistance against high mechanical stresses is a main focus especially for economic and ecological reasons. With much lower density and excellent mechanical properties γ-TiAl alloys are promising candidates to replace the heavy steels and Ni-based super alloys. Protective coatings are necessary to exploit the full potential of gamma titanium aluminides at temperatures higher than 750°C with regard to a much lower oxidation rate. In this study the oxidation resistant and MAX-phase based material Ti₂AlC was investigated as coating material on γ-TiAl deposited by magnetron sputtering. The phase formation was enhanced after the deposition process by heat treatment under high vacuum conditions. This phase should intend the formation of a slow growing and protective Al₂O₃ scale when exposed to air at 950°C. The results of that test will be presented in relation to a non-pre-treated coating highlighting microstructure features by means of SEM and EDS analysis after exposure with regard to oxidation kinetics and lifetimes of the coating systems.