Surface roughness and microstructure of yttria stabilized zirconia EB-PVD coatings

Microstructural properties and surface roughness of ZrO₂-4 mol% Y₂O₃ coating layers fabricated by EB-PVD were investigated as a function of substrate rotation speed during deposition. The coatings were applied to zirconia substrates of the same composition as the coating material. Coating layers consist of porous, aligned columnar grains with a feather-like structure. Specimens deposited at 1 rpm form a wavy columnar structure. The average width of columns in the coating layers increased with increasing substrate rotation speed, with columns capped with a cone- or pyramid-like shape at the surface. The surface roughness as well as porosity of the coating layers also increased with increasing substrate rotation speed. High concentrations of nanopores are found both inside the cores of the columns and within the feather-like features of the columns.