Ti-Al-Cr Based Coatings for High Temperature Oxidation Protection of γ-TiAl

Abstract

Due to much lower density and excellent mechanical properties γ-TiAl alloys are promising candidates to replace the heavy steels and Ni-based superalloys typically applied in the field of aerospace and automotive industry. Protective coatings are necessary to exploit the full potential of γ-TiAl at temperatures higher than 750°C; however, so far no coating system tested has proven sufficient performance for long-term use. The paper is focused on the development of Pt-based coatings produced by magnetron sputtering. Two Pt containing systems with different aluminum contents - PtAl and PtAl2 - were investigated aiming at the formation of a slow growing and protective Al2O3 scale. The oxidation resistance of each coating system was tested under cyclic conditions at 950°C up to 1000 1h-cycles and compared to the oxidation behaviour of pure Pt deposited on γ-TiAl. Investigations of microstructure evolution will be presented observed by means of SEM and EDS analysis after exposure.