Microstructure of ZrO2 thermal barrier coatings applied by EB-PVD

The electron beam physical vapor deposition process (EB-PVD) provides distinctive coatings of a unique columnar microstructure for gas turbine components. The main advantage of this microstructure is its superior tolerance against stresses, erosion and thermoshock, thus giving it a major edge in lifetime. This paper describes recent investigations of microstructure and texture of yttria-partially stabilized zirconia (Y-PSZ) thermal barrier coatings. Close to the substrate a thin zone of varying thickness consisting of equiaxed ZrO2 grains is observed which can be explained by a geometrical model. A fourfold texture is formed on rotated substrates via evolutionary selection of the fastest growth directions. Rotation causes a layered structure of bent columns. Texture and morphology of the coatings are drastically changed under stationary deposition conditions.