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5365 |
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Coupled thermo-mechanical analysis of the ceramic thermal barrier coatings of 8YSZ Gd2Zr2O7 and Gd2Zr2O7/8YSZ double ceramic layer type |
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Grzegorz Moskal* / Silesian University of Technology, Poland Grzegorz Kokot / Silesian University of Technology, Poland Anna Jasik/ Silesian University of Technology, Poland |
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The paper is devoted to thermal and thermo-mechanical analysis of the plasma sprayed thermal barrier coatings (TBC) of different type. The temperature and stress distribution using the finite element method in the microscopic scale is presented. The finite element model is based on the microscopy scan (dimension 5mmx3.5mm) and represent three levels of barrier structure: substrate alloy AMS 5599, bond-coat of NiCrAlY type and ceramic layer of three types: standard ZrO2×8Y2O3, new type material of Gd2Zr2O7 type and solution consisted both of analysed ceramic materials in the form of double layered ceramic thermal barrier coatings (DCL TBC). The layers material properties are fully temperature dependent and coupled thermo-mechanical analysis is performed. The numerical results will be compared with the experimental one. The plasma sprayed thermal coating barrier are the new way for raising the thermal efficiency of the new gas turbine and rotor blades. There are many experimental method for determining their physical properties and investigating the metallographic structure. The TBC work condition are very hard and still the best layer structure, durability and crack resistance are looking for. The research methods come from experiments and numerical simulations. This work presents mainly the numerical simulations of TBCs using the finite element method. This method widely use to solve large class of thermal and mechanical problems is helpful above all in investigating stresses distribution in the TBCs. Taking into account the complicated work conditions, temperature dependent materials, full coupled thermo-mechanical process it is possible to precisely determine temperature, stresses and strain distributions what gives important information from the proper design and manufacturing process point of view. The presented research results are connected with stress distribution in TBC whit three types of ceramic layers: based on the ZrO2×8Y2O3, Gd2Zr2O7 and DCL type Gd2Zr2O7/ZrO2×8Y2O3. Obtained results were verified by experiments in the range were it was possible. Performed analyses shows that differences in stress state in this three cases. Stresses in TBC with Gd2Zr2O7 are nearly twice higher than in the TBC with ZrO2×8Y2O3 what is caused by different thermal expansions coefficient of this two ceramic layers. But in the case of DCL type of insulation layer obtained data suggest that stress in this case is much lower than for ZrO2×8Y2O3 and Gd2Zr2O7 systems. All of layers work fine as the thermal barrier what can be seen from the temperature distributions. Application of the finite element method as the research methodology in TBCs designing and manufacturing extends the possibility of searching the best solutions in this types of advanced structure. |