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Coatings 2018, 8(9), 320; https://doi.org/10.3390/coatings8090320

Capturing the Competing Influence of Thermal and Mechanical Loads on the Strain of Turbine Blade Coatings via High Energy X-rays

1
Department of Mechanical and Aerospace Engineering, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816, USA
2
German Aerospace Center, Institute of Materials Research, Linder Höhe, 51147 Köln, Germany
3
X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
4
Washkewicz College of Engineering, Cleveland State University, 2121 Euclid Ave, Cleveland, OH 44115, USA
*
Author to whom correspondence should be addressed.
Received: 12 July 2018 / Revised: 22 August 2018 / Accepted: 30 August 2018 / Published: 10 September 2018
(This article belongs to the Special Issue Thermal Barrier Coatings)
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Abstract

This paper presents findings of synchrotron diffraction measurements on tubular specimens with a thermal barrier coating (TBC) system applied by electron beam physical vapor deposition (EB-PVD), having a thermally grown oxide (TGO) layer due to aging in hot air. The diffraction measurements were in situ while applying a thermal cycle with high temperature holds at 1000 °C and varying internal air cooling mass flow and mechanical load. It was observed that, during high temperature holds at 1000 °C, the TGO strain approached zero if no mechanical load or internal cooling was applied. When applying a mechanical load, the TGO in-plane strain (e22) changed to tensile and the out of plane TGO strain (e11) became compressive. The addition of internal cooling induced a thermal gradient, yielding a competing effect, driving the e22 strain to compressive and e11 strain to tensile. Quantifying TGO strain variations in response to competing factors will provide a path to controlling the TGO strain, and further improving the lifetime assessment and durability design strategies for TBC systems. View Full-Text
Keywords: thermal barrier coatings; thermal gradient mechanical load; synchrotron thermal barrier coatings; thermal gradient mechanical load; synchrotron
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Manero, A.; Knipe, K.; Wischek, J.; Meid, C.; Okasinski, J.; Almer, J.; Karlsson, A.M.; Bartsch, M.; Raghavan, S. Capturing the Competing Influence of Thermal and Mechanical Loads on the Strain of Turbine Blade Coatings via High Energy X-rays. Coatings 2018, 8, 320.

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