Functionally graded EB PVD coatings

The paper gives the results of an investigation of electron beam evaporation from one source of multicomponent mixtures of metallic and non-metallic materials, prepared in the form of compacted tablets or composite ingots. It is demonstrated that appropriate purpose-oriented selection of components with different vapour pressures at the evaporation temperature allows the structure and properties of gradient coatings to be varied in a broad range. Examples of functionally graded coatings with an outer ceramic layer of oxides and carbides are considered. Special attention is given to thermal barrier coatings of yttria-stabilised zirconia (YSZ) with gradient bond coats of NiAl intermetallic, deposited in one cycle. Mechanisms of vapour flow condensation on the substrate, involving the liquid phase are discussed, that provide a high adhesion of the coating to the substrate. (C) 2002 Elsevier Science B.V. All rights reserved.