Two-source jumping beam evaporation for advanced EB-PVD TBC systems

The continuous increase of the turbine inlet temperature in gas turbines necessitates new TBCs with a temperature capability beyond the current partially yttria stabilized material coatings. The present paper focuses on two-source jumping EB-PVD processed novel candidate layers for future TBC applications. It is shown that mixtures of oxides with widely different vapor pressures can be manufactured by this technique. The microstructure of the layers depends strongly on deposition conditions and on materials properties as well. Partial yttria stabilized zirconia coatings show no differences in microstructure and phase formation if deposited either by two-source jumping-beam or by one-source one-beam evaporation, while for ceria stabilized zirconia coatings large differences mainly in chemistry are found; depending on the jumping frequency multilayers are formed. In mixed silica zirconia coatings, crystalline zircon (ZrSiO4) was formed neither in the as coated condition nor after annealing. Finally, jumping beam experiments allowed a detailed understanding of the growth kinetics of EB-PVD TBCs and the formation of a feather-like structure within the columns.