The effect of substrate temperature on the thermal diffusivity and bonding characteristics of plasma sprayed beryllium

Plasma spraying is under investigation as a method for in-situ repair of damaged beryllium and tungsten plasma facing surfaces for the International Thermonuclear Experimental Reactor (ITER), the next generation magnetic fusion energy device, and is also being considered as a potential fabrication method for beryllium and tungsten plasma-facing components for the first wall of ITER. Investigators at Los Alamos National Laboratoryʹs Beryllium Atomization and Thermal Spray Facility have concentrated on investigating the structure-property relationship between the as-deposited microstructures of plasma sprayed beryllium coatings and the resulting thermal properties of the coatings. In this study, the effect of substrate temperature on the resulting thermal diffusivity of the beryllium coatings and the thermal diffusivity at the coating/beryllium substrate interface was investigated. Results have shown that increases in the beryllium substrate temperature can improve the thermal diffusivity of the beryllium coatings. Results also indicate that the thermal resistance at the interface between the beryllium coating and the beryllium substrate were minimal and showed little dependence on the substrate temperature. The effective bond strength and failure characteristics of plasma spray beryllium on beryllium surfaces were predominately dominated by mechanical interlocking at low substrate temperatures and increased metallurgical bonding at higher substrate temperatures.