Al-rich precipitation in CoNiCrAlY bondcoat at high temperature |
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Authors: | T Koomparkping S Damrongrat P Niranatlumpong |
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Affiliation: | (1) Department of Energy and Materials, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand;(2) National Metal and Materials Technology Center, Pathumthani, Thailand |
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Abstract: | A thermal barrier coating (TBC) is applied on a surface of a gas turbine blade to provide a thermal barrier and oxidation
resistant properties for the components. The ability to resist oxidation of the coating arises from the self-healing, protective
Al2O3 scale on top of the bondcoat, which is formed during service. However, if Al depletion occurs within the bondcoat, the protective
scale will lose its self-healing ability, and hence, its oxidation-resistant property. This paper investigated the depletion
of Al within the bondcoat by studying the microstructure of the bondcoat on a gas turbine blade after it has been in 4000
h service at 1200 °C. The results showed that Al depletion had occurred at different levels throughout the turbine blade.
In the area where Al depletion had not yet occurred, precipitation of an Al-rich phase was detected. Most of the Al was contained
within this phase, leaving only small amount of Al in the surrounding matrix. A well-defined boundary was observed between
the depleted and non-depleted regions. |
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Keywords: | Al-depletion bondcoat precipitation thermal barrier coating thermally grown oxide |
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