Bond coat oxidation and its significance for life expectancy of thermal barrier coating systems

Abstract

AbstractAbstractThe time and temperature dependent evolution of the microstructure of thermal barrier coating systems under isothermal conditions between 950 and 1100 ° C up to 5000 h are investigated for two APS - TBC systems and two EB-PVD systems. Kinetics for the thermally grown oxide thickness values, the β phase depletion underneath the oxide scale and the physical defects in and around the thermally grown oxide are determined by extensive SEM and subsequent interactive image analysis. In the case of physical defects, the size of pores, interacting pore populations and maximum crack lengths are measured. Additionally, the latter are classified with respect to their local orientation in the thermally grown oxide or its vicinity. Finally, the results are discussed with regard to their significance in lifetime modelling of gas turbine components.Keywords: THERMAL BARRIER COATINGLIFETIME MODELLINGOXIDATIONPHYSICAL DEFECTS