Hochtemperaturverschleißschutzschichten für TiAl-Legierungen

Bild Forschungsprojekt
Laufzeit: 01.01.2018 – 30.06.2020
Geldgeber: Bundesministerium für Wirtschaft und Energie über AiF
Bearbeiter: Lukas Mengis
Arbeitsgruppe: Hochtemperaturwerkstoffe

Belonging to the intermetallics, gamma-based titanium aluminides have already been established as high-temperature materials in aerospace applications. In the low-pressure section of the turbine engine they have partially substituted heavier nickel-based superalloys as blade materials because of their outstanding combination of thermo-physical properties. Most notably they possess low density (~3.9-4.2 g/cm³), high-temperature strength as well as good oxidation and creep resistance below 800°C.

However, their oxidation resistance at temperatures above 800°C is insufficient and thus rules out their potential application in the hotter stages of the turbine engine, which would otherwise lead to an additional increase in overall process efficiency. Furthermore, as turbine blades are usually fitted into the turbine disc using a unique dovetail construction, metallic surfaces are inevitably in direct contact under high mechanical loads inducing friction and wear.

As previous studies focus mostly on improving either the oxidation or the wear resistance of the titanium aluminide substrate, a combined approach is undertaken within the scope of this study addressing both drawbacks equally. The so-called MAX phase has been chosen as an appropriate coating candidate for this specific application due to its integrated metallic and ceramic characteristics. Depositions of the MAX phase will be conducted using pack carburisation, nitridation as well as a one-step pack carbo-nitridation.

To begin with, the basic oxidation behaviour of the bare substrate will be investigated at different temperatures and under variation of the exposure time (up to 1000 h). Additionally, the tribological properties of the substrate will be tested at room temperature using a tribometer (pin-on-disk) with various counterpart materials. Finally, coated samples will be tested under long-term high-temperature conditions to investigate their required oxidation resistance, while high-temperature pin-on-disk measurements will be used to characterise the modified wear and friction behaviour.

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Das IGF-Vorhaben Nr. der Forschungsvereinigung DECHEMA e.V., Theodor-Heuss-Allee 25, 60486 Frankfurt am Main wurde über die AiF im Rahmen des Programms zur Förderung der industriellen Gemeinschaftsforschung (IGF) vom Bundesministerium für Wirtschaft und Energie aufgrund eines Beschlusses des Deutschen Bundestages gefördert.

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