Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes

Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes

Bibliographic Details
Main Author: Gledhill, Andrew Dean
Language:English
Published: The Ohio State University / OhioLINK 2011
Subjects:
Materials Science
Thermal Barrier Coatings
TBCs
molten deposits
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=osu1321892196
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-osu13218921962021-08-03T06:04:03Z Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes Gledhill, Andrew Dean Materials Science Thermal Barrier Coatings TBCs molten deposits <p>Thermal barrier coatings (TBCs) are ceramic coatings used on component in the hottest sections of gas turbine engines, used for power generation and aviation. These coatings insulate the underlying metal components and allow for much higher engine operating temperatures, improving the engine efficiency.</p><p>These increase temperatures engender a new set of materials problems for TBCs. Operating temperatures in engines are now high enough for silicate impurities, either present in the fuel or ingested into the engines, to melt and adhere to the surface of the TBCs. The effects of four such impurities, two coal fly ashes, a petroleum coke-fly ash blend, and volcanic ash from the Eyjafjallajökull volcano were tested with conventional yttria-stabilized zirconia (YSZ) coatings, and found to penetrate through the entire thickness of the coating. This penetration reduces the strain tolerance of the coatings, and can result in premature failure. Testing on a newly built thermal gradient burner rig with simultaneous injection of ash impurities has shown a reduction of life up to 99.6% in these coatings when ash is present. </p><p>Coatings of an alternative ceramic, gadolinium zirconate (Gd2Zr2O7), were found to form a dense reaction layer with each of these impurities, preventing further penetration of the molten ash. This dense layer also reduces the strain tolerance, but these coatings were found to have a significantly higher life than the YSZ coatings. Testing with a small amount of ash baked onto the samples showed thirteen times the life of YSZ coatings. When the ash is continuously sprayed onto the hot sample, the life of the Gd2Zr2O7 coatings was nearly twice that of the YSZ.</p><p>Finally, a delamination model was employed to explain the degradation of both types of coatings. This elastic model that takes into account the degree of penetration, differential cooling in thermal gradient testing, and thermal expansion mismatch with the underlying substrate, predicted the failure of YSZ coatings with the observed degree of penetration. The model shows that deposition optimization can be employed to further enhance the life of Gd2Zr2O7coatings.</p> 2011-12-15 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1321892196 http://rave.ohiolink.edu/etdc/view?acc_num=osu1321892196 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Materials Science
Thermal Barrier Coatings
TBCs
molten deposits
spellingShingle Materials Science
Thermal Barrier Coatings
TBCs
molten deposits
Gledhill, Andrew Dean
Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes
author Gledhill, Andrew Dean
author_facet Gledhill, Andrew Dean
author_sort Gledhill, Andrew Dean
title Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes
title_short Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes
title_full Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes
title_fullStr Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes
title_full_unstemmed Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes
title_sort thermal barrier coatings chemically and mechanically resistant to high temperature attack by molten ashes
publisher The Ohio State University / OhioLINK
publishDate 2011
url http://rave.ohiolink.edu/etdc/view?acc_num=osu1321892196
work_keys_str_mv AT gledhillandrewdean thermalbarriercoatingschemicallyandmechanicallyresistanttohightemperatureattackbymoltenashes
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