Physical vapour deposition processes

Abstract

AbstractAbstractPhysical vapour deposition (PVD) is the process whereby metals and alloys may be transferred in the vapour state from one source to another. It was known as early as 1857, and since 1912 has been operated in vacuum form, both experimentally and commercially, for applying coatings and fabricating bulk shapes. Over the years the basic PVD process has been modified and used in a number of different ways, and these have been given different names. The development of this sometimes conflicting and confusing nomenclature is reviewed as an introduction to a discussion of the background and present status of the PVD process for depositing overlay protective coatings on gas turbine components, a process which has been in use commercially for over 15 years. The requirements for this application are very different from those for most other uses, and these are discussed in terms of their effects on the adherence, structure, and post–coating processing of the applied coatings. The limitations of the process, such as required compositional ranges, growth defect tolerance, line–of–sight deposition, low–angle coatings, and the ability to deposit elements having widely different vapour pressures, are considered. The latest forms of the PVD process are discussed in terms of how these limitations affect them. The present status of PVD processes is examined in the light of the current economic climate and future technological developments.MST/283