Progress in coating development for fusion systems

Development of effective and reliable coatings is a key to the viability of most, if not all, fusion blanket systems. The specific purpose and requirements of the coatings vary widely, depending on the blanket concept. The efforts on coating development to date have focused primarily on electrically insulating coatings for the self-cooled lithium concepts with a vanadium alloy structure, and the tritium barrier coatings for the water-cooled, Pb–Li (WCLL) breeder concepts with ferritic steel structures. Although other coating materials are under consideration, most of the effort on the electrically insulating coatings has focused on CaO and AlN coatings on V–4Cr–4Ti alloy structure. Most of the effort on the tritium barrier coating development is focused on Al2O3 coatings formed on aluminized ferritic steels. This paper presents an overview of the status of coating development for the various fusion concepts with emphasis on the materials interaction and chemistry control issues associated with the formation, stability and performance of the coatings.