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Synchrotron X-Ray Diffraction Measurements Mapping Internal Strains of Thermal Barrier Coatings During Thermal Gradient Mechanical Fatigue Loading

Knipe, Kevin and Manero, Albert and Sofronsky, Stephen and Okasinski, John and Almer, Jonathan and Wischek, Janine and Meid, Carla and Karlsson, Anette M. and Bartsch, Marion and Raghavan, Seetha (2015) Synchrotron X-Ray Diffraction Measurements Mapping Internal Strains of Thermal Barrier Coatings During Thermal Gradient Mechanical Fatigue Loading. Journal of Engineering for Gas Turbines and Power, 137 (8), e082506. American Society of Mechanical Engineers (ASME). DOI: 10.1115/1.4029480 ISSN 0742-4795

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Abstract

An understanding of the high temperature mechanics experienced in thermal barrier coatings (TBC) during cycling conditions would be highly beneficial to extending the lifespan of the coatings. This study will present results obtained using synchrotron X-rays to measure depth resolved strains in the various layers of TBCs under thermal mechanical loading and a superposed thermal gradient. Tubular specimens, coated with yttria stabilized zirconia (YSZ) and an aluminum containing nickel alloy as a bond coat both through electron beam-physical vapor deposition (EB-PVD), were subjected to external heating and controlled internal cooling generating a thermal gradient across the specimen's wall. Temperatures at the external surface were in excess of 1000 degrees C. Throughout high temperature testing, 2D high-resolution XRD strain measurements are taken at various locations through the entire depth of the coating layers. Across the YSZ, a strain gradient was observed showing higher compressive strain at the interface to the bond coat than toward the surface. This behavior can be attributed to the specific microstructure of the EB-PVD-coating, which reveals higher porosity at the outer surface than at the interface to the bond coat, resulting in a lower in plane modulus near the surface. This location at the interface displays the most significant variation due to applied load at room temperature with this effect diminishing at elevated uniform temperatures. During thermal cycling with a thermal gradient and mechanical loading, the bond coat strain moves from a highly tensile state at room temperature to an initially compressive state at high temperature before relaxing to zero during the high temperature hold. The results of these experiments give insight into previously unseen material behavior at high temperature, which can be used to develop an increased understanding of various failure modes and their causes.

Item URL in elib:https://elib.dlr.de/98272/
Document Type:Article
Title:Synchrotron X-Ray Diffraction Measurements Mapping Internal Strains of Thermal Barrier Coatings During Thermal Gradient Mechanical Fatigue Loading
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Knipe, KevinUniversity of Central Florida, Orlando, FL, USAUNSPECIFIED
Manero, AlbertUniversity of Central Florida, Orlando, FL, USAUNSPECIFIED
Sofronsky, StephenUniversity of Central Florida, Orlando, FL, USAUNSPECIFIED
Okasinski, JohnAdvanced Photon Source, Argonne National Laboratory, Argonne, IllinoisUNSPECIFIED
Almer, JonathanAdvanced Photon Source, Argonne National Laboratory, Argonne, IllinoisUNSPECIFIED
Wischek, Janinejanine.wischek (at) dlr.deUNSPECIFIED
Meid, Carlacarla.meid (at) dlr.deUNSPECIFIED
Karlsson, Anette M.Cleveland State University, Ohio, USAUNSPECIFIED
Bartsch, Marionmarion.bartsch (at) dlr.deUNSPECIFIED
Raghavan, SeethaUniversity of Central Florida, Orlando, FL, USAUNSPECIFIED
Date:August 2015
Journal or Publication Title:Journal of Engineering for Gas Turbines and Power
Refereed publication:Yes
Open Access:No
In DOAJ:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:137
DOI :10.1115/1.4029480
Page Range:e082506
Publisher:American Society of Mechanical Engineers (ASME)
ISSN:0742-4795
Status:Published
Keywords:Synchrotron X-ray diffraction, Thermal Barrier Coatings, local strain, thermal gradient
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:propulsion systems
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Virtual Engine and Validation methods
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Experimental and Numerical Methods
Deposited By: Bartsch, Dr.-Ing. Marion
Deposited On:23 Sep 2015 13:46
Last Modified:08 Mar 2018 18:42

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