Crystallographic texture evolution in ZrO₂-Y₂O₃ layers produced by electron beam physical vapor deposition

Texture evolution in ZrO₂-4 mol% Y₂O₃ thermal barrier coating layers deposited by electron beam physical vapor deposition (EB-PVD) process was investigated using morphological and crystallographic observation. The preheating temperature and the deposition time strongly influence the structures and orientations of the columnar grains that grow in the coating layer. From the results of X-ray diffractometry analysis, only {1 0 0} planes ((1 0 0) and (2 0 0)) are observed after 120 s in a sample deposited at T _preheat=1211 K. However, {1 1 1} planes could be observed at T _preheat=925 K from 12 to 300 s. In this paper, the kinetics of crystal selection and the resulting orientations of coating layer are discussed on the basis of the 'competitive-crystal-growth model'. This model predicts a linear correlation between the lifetime of a crystal and the reciprocal of the sine of the angle between the fastest growth orientation and the crystal orientation. Experimental measurements of the lifetimes of oriented crystals are in good agreement with estimates based on this model.