Enhanced thermal isolation in porous thermal barrier coatings by the formation of pore guided thermal-shock cracks

Pore structure design is an effective strategy to tailor the thermal isolation capability of thermal barrier coatings (TBCs). Pursuing optimal porosity is crucial to balance the requirements of thermal isolation and mechanical reliability since the pore structure shields thermal heat transfer but increases mechanical degradation. In this work, we investigate how thermal heat transfer couples with fracture propagation in porous TBCs by the using thermo-mechanical coupling phase field model for fracture. The simulated results show that cracks induced by thermal shock favor deflection that is sometimes perpendicular to the direction of heat flow. The thermal conductivity degradation by the transverse cracks significantly impedes thermal heat transfer, leads to enhanced reduction of the effective thermal conductivity of TBCs, decreases the average thermal stress of the substrate, and thus decreases the risk of the crack penetrating into the substrate. The numerical results demonstrate that the phase field method fully considering the thermo-mechanical interaction between cracks and pores can be a useful tool to improve the thermal isolation of porous TBCs under extreme thermal shock loadings through pore structure design.