Plasma-produced erbia coatings for waste reduction in plutonium casting operations

Summary form only given. Disposal of molds used in plutonium casting operations creates a significant waste stream, since such molds are typically only used once or twice, due to the highly corrosive nature of molten plutonium. Erbia (erbium oxide) is inert to molten plutonium, but being a brittle ceramic material, is difficult to make adhere to mold surfaces under severe conditions of thermal expansion mismatch. We report on efforts to utilize an ion implantation process to improve the adhesion of erbia coatings deposited from a cathodic arc derived erbium plasma. Coatings were created using both DC and pulsed cathodic arc sources in a low pressure oxygen background. Ion implantation was achieved by pulse biasing the target to several 10's of kilovolts during some steps in the process. This high energy ion bombardment was found to produce superior coating adhesion, and treated samples successfully resisted attack from molten plutonium in a casting test. The effect of variations in ion implantation parameters, coating parameters, and coating stoichiometry will be discussed.