Effect of porous microstructure on the elastic modulus of plasma-sprayed thermal barrier coatings: Experiment and numerical analysis

Abstract

The effective modulus of thermal barrier coatings (TBCs) can be obtained via different experimental or image-based numerical methods. An alternative method for estimating the effective properties which can reduce a lot of workloads was proposed in this paper. The elastic moduli of plasma-sprayed YSZ coatings with different porosities were obtained through bending experiments combined with digital image correlation (DIC) method. The results show that the elastic modulus decreases with the increasing porosity linearly when the heat treatment time (HTT) reaches more than 1h. The internal pores and cracks will shrink or partially close when exposed to the high temperature environment for a period of time, as a result of the diffusion phenomena of ceramic materials.In addition, the image-based finite element method (FEM) was proposed according to the SEM observation. Several factors of pores and cracks were taken into account to explain the effect of porous microstructure on elastic modulus of coatings. The simulation results show that the crack length has significant effect on the elastic modulus of coatings, while the distance ratio of pores (DRP) was found to be a negligible factor. Finally, a method for the estimation of the effective properties of coatings based on the 2D models and the principle of superposition was proposed and proved to be practicable.