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1102 |
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Wednesday, June 04, 2008, Room 04 10:40 AM Gasturbines 4 Coatings for mobile and stationary turbines, protection against wear, high temperature corrosion and thermal stresses, clearance control coatings for a better efficiency |
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TGO growth and crack propagation in a thermal barrier coating |
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Weijie Chen* / National Research Council Canada, Canada R. Archer / Carleton University, Canada X. Huang/ Carleton University, Canada B.R. Marple/ National Research Council Canada, Canada |
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In thermal barrier coating (TBC) systems, a continuous alumina layer developed at the ceramic topcoat/metallic bond coat interface helps to protect the bond coat from further oxidation and improve the durability of the TBC system under service conditions. However, other oxides such as spinel and nickel oxide, formed in the oxidizing environment, are believed to be detrimental to TBC durability during service at high temperatures. It has been reported that in an APS-TBC system, post-spraying heat treatments in low-pressure oxygen environments could suppress the formation of the detrimental oxides by promoting the formation of an alumina layer at the ceramic topcoat/metallic bond coat interface, leading to an improved TBC durability. This paper presents the influence of post-spraying heat treatments in low-pressure oxygen environments on the oxidation behaviour and durability of a thermally sprayed TBC system with APS-produced ZrO2-8%Y2O3 topcoat and HVOF-produced Co-32Ni-21Cr-8Al-0.5Y (wt.%) bond coat. Oxidation behaviour of the TBCs was evaluated by examining the microstructural evolution of the TBCs, growth kinetics of the thermally-grown-oxide (TGO) layers, as well as crack propagation during low frequency thermal cycling at 1050°C. The relationship between the TGO growth and crack propagation is discussed. |