MICROSTRUCTURES OF Y2O3-STABILIZED ZRO2 ELECTRON-BEAM PHYSICAL VAPOR-DEPOSITION COATINGS ON NI-BASE SUPERALLOYS

The microstructures of ZrO2-20 wt% Y2O3 thermal barrier coatings forme d by electron beam-physical vapor deposition on a Ni-base superalloy h ave been studied by transmission electron microscopy. The coating syst ems consist of several layers, including a superalloy substrate, a bon d coat, an Al2O3 scale, and the PVD coating. The overall ceramic therm al barrier coatings were characterized, with special emphasis being gi ven to the alpha-Al2O3 scale which forms between the bond coat and the ZrO2-Y2O3 coating. The oxide scale exhibited various morphologies in different coating systems; the majority of the porosity formed in this region for all coatings.