Study on Internal Stress of Electrodeposition Layer of High Tungsten Ni-W Alloy

Abstract

This paper introduces the effects of current density on the microstructure, coating composition and internal stress of electrodeposited Ni-W alloys in the citrate system. The effect of carbon content on the internal stress of the coating is also studied by adding 2-Butyne-1,4-diol to increase the carbon content of the coating. The Ni-W alloy is investigated by XRD, SEM, EDS, TEM and XPS methods. The results show that the tungsten presents as a solute within a solid solution of Ni–W, which is FCC structure with a preferred orientation of (111). Both the tungsten content and the current efficiency increase with the increase of the current density. The carbon content dominates the change of the internal stress of the coating, and the higher the carbon content, the smaller the internal stress, because the carbides originating from the decomposition of the complexing agent occupy the position near the grain boundary and it inhibits the shrinkage of the coating when the hydrogen escapes.

Keywords: Electrodeposition, Ni-W alloy, internal stress, carbon content, high tungsten content