Preparation of tungsten coatings on graphite by electro-deposition via Na2WO4–WO3 molten salt system

• Tungsten coatings on graphite were firstly obtained by electro-deposition method via Na2WO4–WO3 molten salt system.
• Uniform and dense tungsten coatings could be easily prepared in each face of the sample, especially the complex components.
• The obtained tungsten coatings are with high purity, ultra-low oxygen content (about 0.022 wt%).
• Modulate pulse parameters can get tungsten coatings with different thickness and hardness.

Tungsten coating on graphite substrate is one of the most promising candidate materials as the ITER plasma facing components. In this paper, tungsten coatings on graphite substrates were fabricated by electro-deposition from Na2WO4–WO3 molten salt system at 1173 K in atmosphere. Tungsten coatings with no impurities were successfully deposited on graphite substrates under various pulsed current densities in an hour. By increasing the current density from 60 mA cm−2 to 120 mA cm−2 an increase of the average size of tungsten grains, the thickness and the hardness of tungsten coatings occurs. The average size of tungsten grains can reach 7.13 μm, the thickness of tungsten coating was in the range of 28.8–51 μm, and the hardness of coating was higher than 400 HV. No cracks or voids were observed between tungsten coating and graphite substrate. The oxygen content of tungsten coating is about 0.022 wt%.