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1526 |
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Wednesday, June 04, 2008, Room 04 2:40 PM Gasturbines 5 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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Role of high temperature creep stress in thermally grown oxide growth of thermal barrier coatings |
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Dowon Seo* / Tohoku University, Japan Kazuhiro Ogawa / Tohoku University, Japan Yasuaki Nakao/ Tohoku University, Japan Dowon Seo/ Tohoku University, Japan Hideo Miura/ Tohoku University, Japan Tetsuo Shoji/ Tohoku University, Japan |
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Thermally grown oxide (TGO) grows at the top / bond coating interface of the thermal barrier coating (TBC) in service. It is supposed that the failures of the TBC occur due to thermal stress and the decrease of adhesive strength caused by the TGO growth. Recently, large local stress has been found to change both the diffusion constant of oxygen through an existing oxide and the rate of chemical reaction at the oxide / oxidized material interface. Since high thermal stress occurs in the TBC, the volume expansion of the newly grown oxide, and centrifugal force, the growth rate of the TGO may change depending on not only temperature but also the stress. The aim of this study is to make clear the influence of stress on the growth rate of the TGO quantitatively. As a result, the thickness of the TGO clearly increases with increase of the amplitude of the applied stress and temperature. The increase rate of the TGO thickness is about 23% when the applied stress is increased from 0 to 205 MPa at 900°C, and about 29% when the stress is increased from 0 to 150 MPa at 950°C. |