Magnetron Sputtered Pt-based Coatings for Oxidation Protection of Titanium Aluminides

Abstract

In the field of aerospace and automotive industry the development of light weight materials with resistance against high mechanical stresses as well as extreme environment 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 superalloys. 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 Pt-based coatings produced by magnetron sputtering. Three Pt containing systems with different aluminum contents - pure Pt, PtAl and PtAl₂ - were investigated aiming at the formation of a slow growing and protective Al₂O₃ scale. Oxidation resistance of all coating systems was tested at 950°C up to 1000 1h-cycles. Investigations of microstructure evolution will be presented observed by means of SEM and EDS analysis after exposure with regard to oxidation kinetics and lifetimes of the coating systems.