Advanced coatings to suppress environmental embrittlement of TiAl alloys (ACETAL)


Bild Forschungsprojekt

Hochtemperaturofen in Betrieb

Period: 2010-01-01 to 2011-12-31
Funder: Federal Ministry for Economics and Technology (BMWI, Germany) via AiF
Project Manager: Laurent Bortolotto
Research Group: High Temperature Materials

With half the density and equivalent mechanical properties of Ni-based superalloys, titanium aluminides aim at progressively replacing these alloys as structural materials for rotating components in aero-engines. A first milestone was recently achieved as General Electric introduced titanium aluminides as blades in the low pressure turbine of the GENx engine powering the Dreamliner. However, because of their poor oxidation resistance at high temperatures (T>700°C), further expansion of technical titanium aluminides to other engine components is a real challenge.

In addressing this problem, the project cluster ACETAL, a consortium of research institutes and companies from 3 European countries, aims at developing advanced coatings capable of protecting the alloy against the rapid diffusion of oxygen at high temperatures which leads to structural damage of the material. Indeed, Al-rich TiCrAl-based coatings are expected to promote the formation of a protective alumina layer at high temperatures while affording more room temperature ductility in the base material. Additionally, as opposed to most ceramic top coats, they exhibit a natural compatibility with the substrate.

Advanced coatings are being produced at DECHEMA-Forschungsinstitut by means of a chemical vapour deposition process using a mixture of inorganic precursors. The substrates, supplied by our project partners, are manufactured from Ti-48Al-2Cr-2Nb ingots (composition of the alloy qualified for flight). The coating effect on the oxidation behaviour of the base alloy is investigated under isothermal (up to 1000°C) and thermocyclic conditions in air. 

The mechanical properties of coated and uncoated samples after atmospheric exposure are compared using 4-point bend tests. The use of the halogen-effect in addition to the advanced coatings is also investigated in the scope of this project. 

The best coating composition and deposition technique for efficient oxidation protection of TiAl, which are being investigated by the different project partners, will lead to a subsequent technical implementation. 

Research institutions such as the DECHEMA-Forschungsinstitut, TU Freiberg, GKSS or ATZ, and SME or larger companies such as GfE, Rolls-Royce or Plansee are part of the ACETAL task force.


Das IGF-Vorhaben Nr. 24EBG 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.

Become a benefactor