Vacuum annealing enhances the properties of a tungsten coating deposited on copper by atmospheric plasma spray

A tungsten (W) coating (∼900 μm) was deposited on a copper (Cu) substrate via the atmospheric plasma spray (APS) technique, and then annealed in vacuum. Measurements of microstructure, density, oxygen content, microhardness and thermal conductivity show that an appropriate thermal annealing treatment can dramatically improve the quality of the coating. The oxygen content was found to drop from 0.48 wt.% before annealing to 0.06 wt.% after; microhardness increased by about 50%; and thermal conductivity nearly doubled. These results indicate that a vacuum-annealed APS-W coating can match or even surpass the quality of W coatings deposited by vacuum plasma spray (VPS). Compared with VPS, annealed APS is a more convenient and cheaper method to obtain W coatings suitable for fusion applications.