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High-energy X-ray phase analysis of CMAS-infiltrated 7YSZ thermal barrier coatings: Effect of time and temperature

Published online by Cambridge University Press:  28 August 2020

Zachary Stein ,
Peter Kenesei ,
Jun-Sang Park ,
Jonathan Almer ,
Ravisankar Naraparaju ,
Uwe Schulz  and
Seetha Raghavan Open the ORCID record for Seetha Raghavan [Opens in a new window]
Zachary Stein
Affiliation:
Department of Mechanical & Aerospace Engineering, University of Central Florida, Orlando, Florida32816, USA
Peter Kenesei
Affiliation:
Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois60439, USA
Jun-Sang Park
Affiliation:
Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois60439, USA
Jonathan Almer
Affiliation:
Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois60439, USA
Ravisankar Naraparaju
Affiliation:
Institute of Materials Research, German Aerospace Centre (DLR), Cologne51170, Germany
Uwe Schulz
Affiliation:
Institute of Materials Research, German Aerospace Centre (DLR), Cologne51170, Germany
Seetha Raghavan*
Affiliation:
Department of Mechanical & Aerospace Engineering, University of Central Florida, Orlando, Florida32816, USA
*
a)Address all correspondence to this author. e-mail: seetha.raghavan@ucf.edu
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Abstract

Calcium–magnesium–alumino-silicate (CMAS) particulates enter the aero-engine in a sandy environment, melt and infiltrate into 7 wt% yttria-stabilized zirconia (7YSZ) thermal barrier coatings (TBCs), reducing their lifetime. This leads to chemical degradation in 7YSZ accompanied by tetragonal to monoclinic phase transformation upon cooling. In this work, electron-beam physical vapor deposition coatings were infiltrated with a synthetic CMAS. Synchrotron X-ray diffraction measurements show that CMAS infiltration at 1250 °C has about 43% higher monoclinic phase volume fraction (PVF) at the coating surface compared to 1225 °C and remains consistently higher throughout the coating depth. Additionally, the increase in annealing time from 1 to 10 h results in a 31% higher monoclinic phase at the surface. Scanning electron microscopy revealed the presence of globular monoclinic phases corresponding spatially with the above findings. These results resolve the impact of time and temperature on CMAS infiltration kinetics which is important for mitigation.

Keywords

infiltration (chemical reaction)X-ray diffraction (XRD)coating

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Article
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Journal of Materials Research , Volume 35 , Issue 17: Focus Issue: Sand-phobic Thermal/Environmental Barrier Coatings for Gas Turbine Engines , 14 September 2020 , pp. 2300 - 2310
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Copyright
Copyright © The Author(s), 2020, published on behalf of Materials Research Society by Cambridge University Press

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