Performance characterization and improvement of tungsten coating atmospheric plasma sprayed with submicron powder

Tungsten coatings were deposited on oxygen free copper substrate via atmospheric plasma spray technique with submicron W powder (600 nm on average). The properties of the tungsten coating such as microstructure, density, microhardness, oxygen content and thermal conductivity were characterized and measured. The results show that spraying with submicron W powder can achieve a relatively dense, high thermal conductivity tungsten coating. In order to improve the performance of tungsten coating, vacuum annealing was applied to the as-sprayed tungsten coatings. The results show that annealing in vacuum after deposition at suitable temperature can significantly improve the quality of the tungsten coating by increasing the grain size and decreasing the porosity. The oxygen content also decreased due to the decomposition of tungsten oxide in vacuum annealing. Compared with the as-sprayed W coating, the thermal conductivity of the annealed W coating was doubly improved.