Development of Magnetron Sputtered TiAl_x Coatings for Optimised Oxidation Protection of Titanium Aluminides for High Temperature Applications

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; however, as yet no coating system tested has proven sufficient performance for long-term use in automotive and aerospace industry. The paper is focused on the development of TiAl_x coatings by means of magnetron sputter process. With various aluminum contents (x ≥ 2,33) a stable TiAl₃ phase on the substrate material should be formed intending the formation of a slow growing and protective Al₂O₃ scale. The effect of different Al-contents on the high temperature behavior at 950°C up to 1500 1h-cycles will be presented highlighting microstructure features by means of SEM and EDS analysis after exposure with regard to oxidation kinetics and lifetimes of the coating systems.