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Endommagement sous sollicitations thermiques et mécaniques d'un aluminiure de nickel et d'une barrière thermique déposés sur un superalliage monocristallin

Abstract : Thermal Barrier Coatings (TBCs) are used to protect turbine blades in the SNECMA-M88 aeroengine. A bondcoat (NiAl-Pt) lies between the substrate, a single crystal superalloy and a ceramic layer (EBPVD ZrO2-7% Y2O3).
The bondcoat rheology has been studied in the brittle and the viscoplastic domains and a fatigue failure criterion has been established and applied to the thermal fatigue behaviour.
The study of the whole TBC is focussed on its interfacial resistance after annealing at 1373K, its behaviour under low cycle fatigue at 1373K and thermal-mechanical fatigue between 373K and 1373K. Annealing at 1373K of adhoc samples, followed by a monotonic tensile test at RT led to cohesive delamination of the interface between the aluminaforming bondcoat and the alumina scale which was affected by cavitation. Spalling of the two oxides could then occur.
Delamination was also studied locally by interfacial indentation tests. Low cycle fatigue tests at 1373K conducted with several different mechanical cycles led to oxidized transverse cracking of the bondcoat. Possible delamination at the alumina/bondcoat interface was related to cavitation. Anisothermal cycling induced multiple cracking at the beginning of the test and cavitation within the alumina scale. The increasing number of cavities and their coalescence led to an adhesive delamination very near the alumina/zirconia interface.
Thermal, mechanical and growth stresses were taken into account in the analyses. The distributions of the alumina scale thicknesses and interfacial cavities sizes have been quantified. These two parametres have been correlated to the substrate curvature in isothermal conditions. A model developed gives an estimation of the critical interfacial energy release rate. In anisothermal conditions, the oxidation kinetics cannot only be related to the substrate curvature. The model developed, based on reinitialisations of the isothermal kinetics, describes well the experimental results.
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https://pastel.archives-ouvertes.fr/tel-00311996
Contributor : Anny Murad-Bickard <>
Submitted on : Sunday, August 24, 2008 - 1:53:56 AM
Last modification on : Thursday, September 24, 2020 - 6:30:04 PM
Long-term archiving on: : Thursday, June 3, 2010 - 6:47:36 PM

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  • HAL Id : tel-00311996, version 1

Citation

Anny Murad-Bickard. Endommagement sous sollicitations thermiques et mécaniques d'un aluminiure de nickel et d'une barrière thermique déposés sur un superalliage monocristallin. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 1998. Français. ⟨tel-00311996⟩

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