Pulse Reverse Deposition of Thick Tungsten Coating

Tungsten has a very high melting point, very high strength, very small electron overflow work, and good chemical and chemical properties such as good chemical stability and high temperature conductivity. Therefore, tungsten has excellent properties in the electronics industry and aerospace technology. Application prospects, molten salt electrodeposition is a method for preparing high-quality metals, with its simple equipment composition and operation methods, as well as its good bonding ability and other advantages have been widely concerned.

A method of pulse reverse electrodeposition of thick tungsten coating has been proposed to solve the problems of low electrodeposition efficiency, uneven coating distribution and uneven surface in the existing single pulse electrodeposition of thick tungsten coating.

A.Pretreatment: The low activation steel plate and tungsten plate were cut into sheets by wire cutting, and then grinded with 240 #, 500 #, 800 # sandpaper in turn. Then the surface of anode and substrate was cleaned by ultrasonic wave with acetone and dried for reserve.

B.Molten salt disposition: Before molten salt disposition, sodium tungstate and tungsten trioxide were dried at 250 ℃ for 12 h. Sodium tungstate and tungsten trioxide with molar ratio of 3:1 were grinded and mixed evenly and then put into a high-purity alumina crucible. The crucible was heated to 850 ℃ in a resistance furnace. The crucible was kept warm for use.

C.Pulse reverse electrodeposition: the treated low-activation steel plate and tungsten plate were connected by platinum wire and immersed completely in molten salt, the low-activation steel plate was cathode, the tungsten plate was anode, and the distance between the anode and cathode was 10 cm. Before electrodeposition, the substrate surface impurities were removed by anodic electrodeposition for 5 minutes and current density of 5 mA cm^-2.

D.Ultrasonic cleaning: The electrodeposited samples were ultrasonic cleaned for 30 minutes in 2.5 M NaOH solution to remove the impurities attached to the surface and obtain tungsten coating. The thickness of tungsten coating obtained is 220 um.

The surface roughness of tungsten coating is controlled. The thick tungsten coating is compact, smooth and crack-free. Compared with the single-phase pulse electrodeposition, the highly inhomogeneous anodic current distribution caused by the reverse current can make the protruding part of the coating dissolved and smoothed, and the concentration of metal ions on the cathode surface can be rapidly increased, thus reducing the concentration polarization, thus resulting in the formation of the prepared tungsten. The coating surface is more smooth and the electrodeposition efficiency is increased.

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