Effect of pulse current parameters on microstructure of tungsten coating electroplated from Na2WO4-WO3-NaPO3

The tungsten coatings with low oxygen content were prepared on copper alloy substrate by pulse electroplating in Na2WO4-WO3-NaPO3 molten salt. A series of tungsten coatings with compact morphologies were successfully obtained under various conditions. The influences of current density, duty cycle and period on tungsten grain size and coatings thickness were investigated. The results demonstrated that current density was the most important factor influencing tungsten grain size, which had a positive correlation with current density. The thickness of coating decreased when the current density was up to 80 mA cm−2. However, the tungsten grain size, tungsten coating thickness and current efficiency changed a little with the increase in pulse periods.