Investigation of Vapor Phase Deposited Columnar Plasma Spray Coatings

Abstract

Abstract The relatively new PS-PVD method (Plasma Spray – Physical Vapor Deposition) allows for an almost complete evaporation of the spray powder by means of a high energy input and a low ambient pressure. On the substrate to be coated, the spraying material condenses to columnar, feather-like structured layers as are known from the EB-PVD process (Electron Beam – Physical Vapor Deposition). These layer structures are of interest in applications in which high strain tolerances are required, such as for thermal barrier coatings in gas turbines where cyclic heating and cooling of the coatings takes place. Courtesy of the high growth rate, PS-PVD can represent a more cost-effective alternative to EB-PVD. The main difference compared to EB-PVD coatings is the higher porosity of the PS-PVD coatings. However, this higher porosity leads to difficulties during the preparation when coatings are characterized. This publication describes how YSZ-coatings (Yttrium-stabilized zirconia) produced by means of PS-PVD are characterized with regard to specific surface area, density, pore distribution, hardness, and sintering activity and compared with EB-PVD coatings.