Study on thermal resistance performance of 8YSZ thermal barrier coatings

Abstract

The application of ceramic thermal barrier coatings (TBCs) can significantly increase gas turbine performance. The microstructure of TBCs fabricated by APS and EB-PVD is remarkably different. The thermal and mechanical properties of TBCs with the same material are determined by its microstructures. In order to establish structure-property relationships of TBCs with complex inhomogeneous geometry, in this work, various 3D-microstructures of TBCs were reconstructed using the geometric reconstruction software developed by our team. A three-dimensional model based on Lattice Bolzmann method (LBM) was developed to investigate the heat transfer behaviors in TBCs. The effect of microstructure parameters such as porosity, pore size and pore shape on the effective thermal conductivity of TBCs was studied in detail. The relationship between microstructures and effective thermal conductivity of TBCs was obtained. The calculated values of the effective thermal conductivity of 3D-TBCs agree well with the experimental values, and all relative errors are less than 4%. It can be found that the layered coatings should have larger size pores, and the columnar coatings should have smaller size pores. This can make the internal temperature distribution of TBCs more uniform. The effect of pores size on the thermal conductivity of two types of TBCs is different, but their thermal conductivity increase with the increase of porosity. The effective thermal conductivity of the columnar TBCs with the same porosity decreases with the decrease of pores size, but that of the layered TBCs increases with the decrease of pores size. The pores shape has a great influence on the effective thermal conductivity of the coating, especially for high porosity columnar coating. The effective thermal conductivity of the columnar coatings logarithmically increases with the length of the elongated pores, and it is increased by 21.6% when the porosity is 20%. However, the effective thermal conductivity of the layered structure coatings logarithmically decreases with the length of the elongated pores. The results will provide us a theoretical guide to design TBCs with a high thermal insulation property.