Effect of substrate rotation on texture evolution in ZrO 2-4 mol.% Y 2O 3 layers fabricated by EB-PVD

Abstract

Changes in the crystallographic texture of thermal barrier coatings (TBCs) produced by electron beam physical vapor deposition (EB-PVD) as a function of substrate-rotation speed have been investigated using SEM, X-ray diffraction and pole figure analysis. It is demonstrated that the substrate rotation strongly influences the morphologies and orientations of the EB-PVD TBC layers. During stationary deposition, (111) planes become oriented parallel to the substrate surface and the deposited layer forms a dense structure instead of the conventional columnar texture. Moreover, the surfaces of stationary samples consist of piles of triangular facets with no particular in-plane orientation. In contrast, when the substrate is rotated, (100) planes form parallel to the surface and many pyramidal facets are observed on the surface by SEM. Columnar grains grew in layers deposited on substrates rotated at speeds from 1 to 10 rev./min. As the rotation speed increased, the width of the columns became thinner and the in-plane orientation became more pronounced. At slow rotation speeds, such as 1 rev./min, the columns developed a wavy structure. In this article, the curvature of the columns is estimated from theory. The difference in the theoretical curvature and that measured experimentally suggests that the shadowing effect has a strong influence on texture growth in EB-PVD TBCs.