Structure Design Of Thermal Barrier Coatings Based On The Numerical Simulation Of Residual Stress

Due to the difference between the coefficient of thermal expansion (CTE) of termal barrier coatings (TBCs) and Ni-based substrate, the residual stress which usually generate during the process of preparation and service will greatly affect the performance of the substrate. As the material with mesh or porous structure possess good strain tolerance, the accumulated stress in TBCs can be reduced by introducing bond coating manufactured with this kind of material. This paper simulated the distribution of residual stress field in the manufactring and the practical working condition. The influence of the shape and size of the structured layer on the residual stress and the performence of thermal shock resistance in thermal barrier coatings were explored. From this work, the following conclusions are drawn:(1) A composite layer was designed by adding a bond coating layer and a structured layer between the ceramic layer and the substrate. With this composite layer the residual stress of TBCs under manufacturing could be effectively reduced. The tensile stress in the X direction decreases. It also releases the stress concentrated around the mesh layer.(2) The appropriate ratio of the spacing to the width of the structured layer is from 4 to 5. With this proportion, the internal stress of thermal barrier coatings and the tensile stress of the interface between the ceramic coat and bond coat reduced significantly. And the residual stress state could improved effectively.(3) Introducing a structured layer could effectively reduce the residual stress in the X direction when the TBCs is under the thermal shock. However it could cause the increase of tensile stress in the Y direction during the heating period. And the thicker the ceramic layer, the higher the tensile stress will be.(4) For different 3-dimensional shaped layer in the TBCs, the residual stress filed was similar. But their stress level were different. The residual stress in the thermal barrier coatings with a hexagon structured layer was lowest under the working condition.