Investigation of plasma-sprayed laminates for high-temperature melting operations

Melting of reactive metals, such as zirconium (Zr), is normally accomplished either by vacuum-arc skull melting using consumable electrodes or by vaccum-induction melting, which is limited to small castings using water-cooled copper crucibles. An alternate process is being proposed to vacuum-induction melt large castings in a coated graphite crucible. The laminated coating would consist of plasma-sprayed layers of metal and ceramic that are designed to withstand temperatures approaching 2000{degrees}C while maintaining enough integrity to prevent contamination of the melt with carbon (C). This paper describes the selection process, experimental results, and feasibility of using laminated coatings that are plasma sprayed on graphite crucibles for melting Zr.