Fabrication of tungsten coatings and monoliths using the vacuum plasma spray process

Abstract Tungsten is used in space nuclear power and propulsion applications for heat pipes, nuclear fuel cladding, and radiation shields. In this study, heat pipes were fabricated by vacuum plasma spraying tungsten powder onto tungsten tubes made with the chemical vapor deposition process. Five experiments were conducted using a statistical design of experiment. The varied parameters included electrical current, secondary-to-primary gas flow ratio, and total flow. The coating attributes evaluated were thickness, porosity, microhardness, surface roughness, and grain structure. After the tungsten samples were thermal cycled in a vacuum, the coating qualities were evaluated with respect to the influence of the processing parameters. This work presents a parameter-property-performance relationship for the process and an optimized coating design predicted by the Taguchi analysis.