8 - Development of plasma spray-physical vapor deposition for advanced thermal barrier coatings

Abstract

Growing demands on high-performance thermal barrier coatings (TBCs) have promoted the development of new materials and advanced manufacturing technologies. Plasma spray-physical vapor deposition (PS-PVD) is a novel coating technology, which has attracted increasing attention in recent years due to its promising potential in processing various functional coatings, such as thermal/environmental barrier coatings. Depending upon the specific process conditions, deposition may be in the form of very fine molten droplets, vapor phase deposition, or a mixture of them. On the one hand, droplet-dominated deposition produces a very fine lamellar microstructure which can be much thinner but nevertheless dense compared to conventional plasma spray coatings. On the other hand, the vapor-deposited coatings tend to have columnar microstructures that are similar to coatings produced by electron beam-physical vapor deposition (EB-PVD). Finally, unlike EB-PVD or traditional plasma spraying, evaporated feedstock material can be transported to non-line-of-site locations to be deposited and form a coating even there. These features make PS-PVD a promising process for the manufacture of TBCs. This book section reviews the worldwide research done on PS-PVD to manufacture TBCs. The chapters follow the three stages of energy transfer in thermal spraying: generation of a hot working gas jet, interaction of feedstock and hot gas, and feedstock deposition on the substrate and coating growth as complete and up-to-date as possible. At the end, a corresponding outlook comprising also other applications than TBCs is given. By this book section, a comprehensive, complete, and up-to-date understanding can be passed to the readers.