The Radiation Properties Of Air Plasma Spraying Thermal Barrier Coatings

Thermal barrier coatings(TBCs)are comprehensively used in aero-gas turbines to protect alloy components from high temperature,due to excellent thermal shock resistance,high stability under high temperature and good insulation performance.As the inlet temperature of aero-gas turbines is increasing,the wavelength of energy radiated from hypothermal gas is analogous to the size of microstructures inside thermal barrier coatings.Radiation heat transfer through the coatings holds a bigger portion of the total transferred heat,and the microstructures have a profound effect on the thermal radiation properties of TBCs.In this work based on the structures generated by Quartet Structure Generation Set algorithm,a Finite-Difference-Time-Domain method is employed to investigate the microstructural effects on the thermal radiation properties of TBCs.The results show that porosity and pore size as well as pore shape have significant influence on the radiation heat transfer through TBCs,and the volume scattering inside the coatings is a crucial factor to the radiation properties of TBCs.An optimized microstructure with the thickness of 50 microns is proposed to make the thermal barrier coating reach a total blackbody radiation reflectance of 0.837.Besides,air plasma spraying functionally graded thermal barrier coatings(APS FGTBCs)are fabricated and scanned by SEM to investigate their radiation properties by experiment.The experimental results show that thickness and porosity along with the components of each layer can heavily affect the hemispherical reflectance of FGTBCs.A larger thickness of top ceramic coat can improve the insulation performance and keep a good mechanical property as well.This work is a good guidance and reference for future fabrication improvement and study on radiation properties of TBCs.