Characterisation of tungsten coatings by pulsed current plating from molten salt in air atmosphere

摘要

Pure and compact tungsten coatings with high (200)-orientation were successfully electro-deposited from Na_2WO_4-WO_3 binary oxide molten salt by direct and pulse current techniques on copper based alloy substrate in air atmosphere at 1173 K. The tungsten coatings and copper alloy substrates combined well with no obvious voids and cracks. In addition, the influence of pulse plating on the microstructure, crystal structure and Vickers microhardness of coatings, adhesive strength between coatings and substrates as well as the current efficiency was investigated. It was also observed that applied pulse current led to tungsten coatings with better mechanical properties than those obtained by direct current plating. In addition, a tungsten coating of 500 μm which had lower oxygen content and higher adhesive strength than the coating obtained by the plasma spray method was obtained.