Applied Surface Science, Vol.317, 867-874, 2014
Effect of direct current density on microstructure of tungsten coating electroplated from Na2WO4-WO3-NaPO3 system
Pure tungsten coating with body-centered cubic (bbc) structure was successfully electrodeposited from Na2WO4-WO3-NaPO3 molten salt at 1153K in atmosphere. The coatings comprised an inner layer of tooth-like grains and an outer layer of columnar grains with a thin diffusion layer of tungsten in the Cu substrate. The effects of current density and electrodeposition duration on the morphology and microstructure of the coatings were investigated in this paper. With increasing of current density from 50 to 80 mA cm(-2), the grain size of the tungsten coating increased from 7.01 mu m to 12.44 mu m. With the increase of the current density, the thickness of the coating changed from 25.92 mu m to 34.40 mu m, and then dropped to 29.72 mu m. The preferred orientation of the coatings changed from (2 2 0) to (2 1 1). With the increasing of duration, the grain size and thickness of tungsten coatings increased while the (2 1 1) favored orientation dot not changed. Because of the low current efficiency at long duration of direct current electrodeposition, it should not be suitable for the electroplating of thick tungsten coating. (C)) 2014 Elsevier B.V. All rights reserved.