The microstructure of a NiCoCrAlY bond coat (BC) of a thermal barrier coating (TBC) system is investigated in dependence on the heat treatment temperature between 770 and 980 degrees C by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Besides the major gamma and phases, additionally gamma precipitates within the beta phase, alpha-Cr precipitates within the phase, grains of the Cr-rich intermetallic sigma phase and M23X6 phase occur. The gamma' precipitates are observed within the bond coat up to a certain distance from the substrate depending on the temperature. This range decreases with temperature between 920 and 800 degrees C linearly. At higher temperatures, almost no gamma' precipitates are detected. The a-Cr precipitates within the grains are found within all [ grains for heat treatment temperatures below 770 degrees C. For higher temperatures up to 860 degrees C, they exist only within p grains near the substrate and are not proven for temperatures higher than 890 degrees C.