CMAS penetration-induced cracking behavior in the ceramic top coat of APS TBCs

Abstract The penetration of calcium-magnesium-alumino-silicate (CMAS) is one of the most vital factors inducing the failure of air plasma sprayed thermal barrier coatings (APS TBCs). In present study, a two-dimensional periodical model considering the microstructures in ceramic top coat (TC) is built to study the cracking behavior in the TC of APS TBCs penetrated by CMAS during the cooling process. The CMAS penetration process is considered by filling the microstructures with the same shape of CMAS. The results show that CMAS penetration into the microstructures of the TC changed the stress distribution around the microstructures and induced a mixed crack type here. A microstructure with a relatively sharper geometry will experience a more severe stress state when penetrated by CMAS. The material discontinuity due to CMAS penetration also causes a slightly higher stress level around the microstructure at the CMAS deposit/TC interface, the CMAS penetrated layer and TC/BC interface. Thus, the horizontal cracks are easier to initiate from the microstructures with sharper geometry in these three regions.