Oxidation study of Pt–Al based coatings on γ-TiAl at 950 °C

In the present study, Pt-based aluminide coatings were deposited on γ-TiAl (Ti–45Al–8Nb–08C; at.%) by magnetron sputtering and tested under high temperature conditions. The Pt-content in the layer was varied (31, 47 and 100 at.%) to find an optimized oxidation resistant coating. The Pt-53Al coating showed the best oxidation resistance at 950 °C due to the formation of a continuous thin alumina layer on top compared to the fast oxidizing pure Pt and aluminum rich Pt–69Al coatings. Depending on the testing time different Pt–Ti–Al phases were formed below the grown oxide layer which is caused by the outward diffusion of Ti and the inward diffusion of Pt at the interface between coating and base material, respectively. Beside mass gain measurements microstructural examinations were performed via scanning electron microscopy (SEM), energy-dispersive X-Ray spectroscopy (EDS) as well as X-Ray diffractometry (XRD) to study the evolution of phase formation