Influences of the near-spherical 3D pore on failure mechanism of atmospheric plasma spraying TBCs using a macro-micro integrated model

The near-spherical 3D pores in the thermal barrier coatings (TBCs) by atmospheric plasma spraying (APS) affect the thermal insulation and anti-spalling performance of the coating. To explore the effects of near-spherical 3D pores on the coating failure, a macro-micro integrated model is developed. The randomly distributed pores are implanted into the ceramic layer inside the micro region by the secondary development of Python program. The dynamic propagation, coalescence, or branching of cracks in the ceramic layer are achieved by embedding cohesive elements between adjacent solid elements. The effects of pore characteristic parameters: porosity, aspect ratio, and orientation angle on the crack evolution are investigated. In addition, the effect of TGO on the ceramic cracking is also examined in the porous model. The results show that the stress concentration near the near-spherical pores can induce early crack initiation. Regular spherical pores with a porosity of about 10% are more conducive to the improvement of coating life. When a large number of near-spherical 3D pores appear, TGO thickening still induces premature spallation of the coating. These results can provide important theoretical guidance for the advanced TBC system design with long lifetime.