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Detailed Program
Paper Number : AD-I02
Time Frame : 15:25~15:50
Presentation Date : Thurseday, 27, November
Session Name : Advanced Coating for Gas Turbines
Session Chair 1# : Yoonsuk Oh
Session Chair 2# : Shunkichi Ueno
Mechanical Behavior of Thermal Barrier Coatings after Thermal Shock using Spherical Indentation Analysis
Kee Sung LEE
KOOKMIN UNIVERSITY
Thermal barrier coating (TBC) is exposed to high temperature from 1100 up to 1600oC during gas turbine operation, by thermal cycling and thermal shock. The thermal expansion coefficient mismatch between ceramic topcoat and metallic bondcoat during thermal shock or cycling causes delamination of coating layer. Sintering of ceramic topcoat during thermal shock or cycling is the other issue to cause the mismatch. Therefore evaluations on the mechanical behavior of thermal barrier coatings after thermal shock are important issue to understand the lifetime of thermal barrier coating.
Mechanical durability are tested in terms of failure modes of thermal barrier coatings. For example, the mode of foreign object damage (FOD) has been studied recently, which can cause cracks at high temperature by particle impact. The other failure mode, erosion, may lead to progressive loss of thickness during operation. Mechanical fatigue by vibration causes damage accumulated failure of thermal barrier coatings.
In this study, materials and structures are designed in the thermal barrier coatings during APS (air plasma spray) and EBPVD (electron beam physical vapor deposition) coatings of YSZ (yttrium stabilized zirconia). Some coatings are conducted using Gd2Zr2O7 (gadolinium zirconate) material. Thermal shock tests between 1100oC and room temperature are conducted for 800~1200 cycles in air. Mechanical deteriorations are evaluated by load-displacement behavior from ball-indentation test as shown in Fig. 1. Additionally, the wear tests are conducted and compared in the thermal barrier coatings using the same spherical ball.
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