Degradation study of 7Â wt.% yttria stabilised zirconia (7YSZ) thermal barrier coatings on aero-engine combustion chamber parts due to infiltration by different CaO-MgO-Al2O3-SiO2 variants

Furnace cycle tests (FCT) were conducted at 1135 °C on TBC coated buttons with and without CMAS. The extent of TBC damage strongly correlates to the CMAS composition. The presence of Ca-sulphate (CaSO4, anhydrite) in the CMAS plays a large role in damaging the 7YSZ and infiltration depth of CMAS. With raising temperature, the depth of infiltration increases rapidly and the CMAS has penetrated completely throughout the TBC thickness at 1250 °C. In addition, the time to failure of the TBCs strongly depended on the type of CMAS deposited. The life time of the samples with CaSO4 containing CMAS was found to be the lowest compared to the samples without CMAS and with the CaSO4 free CMAS variant.