V. Simova1, S. Brown1, M. Cavarroc2, S. Knittel3, L. Martinu1 and J.E Klemberg-Sapieha1

1) École Polytechnique de Montréal, Department of Engineering Physics, Montréal, QC H3T 1J4, Canada
2) SAFRAN Tech - Rue des jeunes bois, Chateaufort, CS 80112, 78772 Magny-les-Hameaux, France
3) SAFRAN Aircraft Engines - Site Evry-Corbeil Rue Henri Auguste Desbruères - BP81 91003 Evry Cedex, France

γ-TiAl based alloys are promising candidates to replace Ni-based superalloys in the low-pressure stages of turbines due to their low weight and excellent mechanical properties. However, their application is limited by severe oxidation at temperatures above 750°C. The development of protective overlay coatings is necessary to increase the service temperature range of the γ-TiAl alloys. Amorphous Si‒B‒C‒N coatings possess very high-temperature stability and oxidation resistance. However, their use on γ-TiAl substrates is limited by a large mismatch of thermal expansion coefficients. In this work, Si‒B‒C‒N coatings were prepared by pulsed dc and rf magnetron co-sputtering from Si and B4C targets in Ar + N2 gas mixtures. The coating adhesion was promoted by deposition of an amorphous Si interlayer. Isothermal oxidation tests were conducted at 800°C for 100 hours in laboratory air. Stable amorphous Si‒B‒C‒N coatings exhibited significantly reduced mass gain and oxidation rate constant compared to uncoated γ-TiAl, indicating an efficient protection against high-temperature oxidation.