Development of a plasma coating system for induction melting zirconium in a graphite crucible

A plasma coating system has been developed for induction melting zirconium at 1900 C using a graphite crucible. This laminated coating system consists of plasma spraying the following materials onto the graphite: (1) molybdenum or tungsten, (2) a 50% blend by weight of the metal powder and calcia-stabilized zirconium oxide, and (3) calcia-stabilized zirconia followed by painting a final coating of nonstabilized zirconia on top of the plasma-sprayed coating system. Zirconium was melted in argon using both laminating systems without any degradation of the graphite crucible and with only a minimal amount of carbon absorption. This novel approach that is being proposed as an alternative method of melting zirconium alloys offers substantial cost savings over the standard practice of electric arc melting using a consumable electrode.