OPTIMIZED COATING PROCEDURE FOR THE PROTECTION OF TiAl INTERMETALLIC ALLOY AGAINST HIGH TEMPERATURE OXIDATION

AUTHOR/S: F. Arcobelloa, M. Tuluia, S.Sabbadinib, F. Pellisserob, M. Sebastianic, E. Bemporadc a Centro Sviluppo Materiali S.p.A. b AVIO S.p.A. c University of Rome “Roma Tre”, Mechanical and Industrial Engineering Department

ABSTRACT

The interest for TiAl intermetallic alloys is growing in the last years because of their excellent ratio between mechanical properties and density.A TiAl3 layer was obtained on the surface of Ti-Al intermetallic samples, depositing an Al coating by arc Physical Vapour Deposition, followed by a thermal treatment. The microstructure and the composition of the coating were characterised before and after the thermal treatment by Scanning Electron Microscopy, X-Ray Diffraction, Focused Ion Beam and Glow Discharge Optical Emission Spectroscopy. Layer investigated by means of scratch tests and nano-indentation. Static oxidations at 1123 K and thermal cycling between 1073 K and room temperature up to 800 cycles were carried out on coated and uncoated samples, in order to study the effect of the coating on the oxidation resistance of the samples. The aluminide coating provides a protection against oxidation in air at the considered temperatures due to its ability to form a continuous Al2O3 scale on the surface by the transformation of TiAl3 in TiAl2.

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