EB-PVD Y2O3- and CeO2/Y2O3-stabilized zirconia thermal barrier coatings - Crystal habit and phase composition

ZrO2-based ingot sources with stabilizing oxides of 6.5 and 20 wt.% Y2O3 and 25/2.5 wt.% CeO2/Y2O3 respectively were used to deposit thermal barrier coatings (TBCs) on rotating cylindrical electron beam physical vapour deposition (EB-PVD) NiCoCrAlY-coated IN 100 substrates by reactive high rate EB-PVD. The TBCs were investigated by scanning electron microscopy, X-ray fluorescence and X-ray diffraction. The phases within the TBCs were t' tetragonal for 6.5 wt.% Y2O3-ZrO2 and cubic for 20 wt.% Y2O3-ZrO2 TBCs. The phases found in ceria-stabilized TBCs were tl, cubic and monoclinic depending on the compositional fluctuations within the layers. Compositional variations were due to wide differences in the respective vapour pressures of the various oxides in ceria-stabilized ingot sources which become effective in single-source EB-PVD processing. The apparent crystal habits in the TBCs were correlated with process parameters, phases and chemistry and With regard to structural growth models.