Abstract No.:
2618

 Scheduled at:
Tuesday, September 27, 2011, Saal A 11:50 AM
Aviation Industry 1


 Title:
Improving long term oxidation protection for gamma-TiAl substrates

 Authors:
Thomas Frederik Linke* / Institut für Oberflächentechnik RWTH Aachen University , Germany
Kirsten Bobzin / RWTH Aachen University IOT - Surface Engineering Institute, Germany
Thomas Schläfer/ RWTH Aachen University IOT - Surface Engineering Institute, Germany
Thomas Warda/ RWTH Aachen University IOT - Surface Engineering Institute, Germany
Markus Brühl/ RWTH Aachen University IOT - Surface Engineering Institute, Germany

 Abstract:
For improving next generation jet engines, material development is a key element, at which high temperature stability and weight reduction are among the most important objectives. Gamma Titanium Aluminide, a potential material for the application in aviation turbine industry is a lightweight alloy, characterized by high mechanical load capacity. However due to oxidation, operation of Gamma Titanium Aluminides is currently limited to temperatures up to approximately 700 °C. Higher temperatures can lead to the formation of instable mixed oxides, leading to fast chipping and material diminution. In previous work, a thermal spray multilayer system showed promising results regarding oxidation behaviour, which encouraged further research activities. Diffusion of substrate material was successfully inhibited by a ceramic ZrO2 coating as well as building up a dense and stable oxide layer could be achieved by additional application of an MCrAlY top coat, leading to improved oxidation resistance and thus showing feasibility. In this work the main focus for development was put on enhancing adhesion and lowering residual stresses of the coatings in order to allow long term and cyclic testing without delamination taking place. Being a very brittle material, Gamma Titanium Aluminides require special surface treatment to enable roughening which is crucial for a strong mechanical bond between substrate and coating. Alternatives to grid blasting as a standard preparation method were investigated. These were Micro-Abrasive Blasting, blasting at elevated temperature to allow a more ductile behaviour and adding a third Layer to act as a bond coat. The paper will highlight the implications by means of these measures and will also show the present development status of the multilayer system on the basis of EDX line scans after thermal exposure.


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