Microcrack propagation induced by dynamic infiltration of calcium-magnesium-alumino-silicate in columnar structures for thermal barrier coatings

Columnar-structured thermal barrier coating systems (TBCs) possess a strain tolerant columnar microstructure wherein the gaps between the columns are filled with high-porosity oxides. A numerical model is proposed to estimate the stress fields of the microcrack induced by calcium-magnesium-alumina-silicate (CMAS) infiltration and microcrack propagation behavior in the yttria stabilized zirconia column induced by dynamic CMAS infiltration is studied using the extended finite element method. The results demonstrate that both the stress and energy release rate near microcracks were found to dramatically increase when CMAS reached a microcrack. The present analysis reveals that the vertical cracks easily initiate from the microstructure column and coalesce with adjacent horizontal and vertical pores, thereby resulting in premature failure of TBCs via delamination.

Automated summary

Columnar-structured thermal barrier coating systems possess a strain tolerant microstructure, but the stress and energy release rate near microcracks increase significantly when CMAS infiltration occurs. Vertical cracks easily initiate from the microstructure columns and coalesce with adjacent pores, leading to premature failure of TBCs.