CMAS degradation of EB-PVD TBCs: The effect of basicity

The columnar, high porosity microstructure of electron-beam physical vapour deposited (EB-PVD) TBCs, typically found on high pressure turbine blades, makes them particularly susceptible to CMAS molten deposit attack. This paper investigates the effect of modifying the chemical composition of molten CMAS deposits on the degradation mechanisms of EB-PVD TBCs. This paper identifies a parameter termed “basicity index” which can be used to evaluate the severity and damage caused by these molten deposits to TBCs. It is believed that the higher temperatures expected to be observed in next generation aero-engines coupled with sand/dust chemistry varying around the world, and then basicity-driven TBC degradation will become more prevalent.