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| Abstract No.: |
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Scheduled at:
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Tuesday, June 03, 2008, Auditorium 2 1:40 PM
Gasturbines 3
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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| Title: |
Self healing thermal barrier coatings
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| Authors: |
Wim G. Sloof / Delft University of Technology
Department of Materials science and Technology, The Netherlands
Vadym Kochubey* / Delft University of Technology, Department of Materials Science and Engineering, The Netherlands
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| Abstract: |
A high temperature coating system comprises a thermal barrier coating (TBC) on top of a bond coating (BC) with a thermally grown oxide (TGO) layer in between. The TBC is made of partially yttria stabilized zirconia (PYSZ) to allow higher operation temperatures. The BC is usually composed of a NiCoCrAlY alloy, which protects the underlying substrate material. This part of the coating system has proven to exhibit excellent self-healing behavior, because it repairs damage of the protective TGO layer by forming alumina during operation of the turbine engine. The TBC, however, does not show any self-healing behavior despite being one of the most critical parts of the coating system for the lifetime of a coated component. The coating system life span is set by the development of crack patterns due to stresses induced during heating and cooling. These cracks coalesce and ultimately lead to failure by delamination of the coating.
To heal these cracks particals are included in the TBC consisting of a carrier element alloyed with stabele oxide forming elements as healing agent. The carrier element forms a volatile oxide and will leave the coating via the crack path thereby compensating for the volume increase upon oxidation of the healing agent. The healing agent will be released and form a stable solid oxide at the front of the crack gap.
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