Wetting of Surface and Grain Boundaries in Tungsten with Melted Nickel

Abstract

The paper describes the wetting of polycrystalline and bicrystalline tungsten samples. A process flow chart is described for wetting solid tungsten with molten nickel in a vacuum at temperatures between 1550 and 1800°C. The structure of the samples was studied using scanning electron microscopes equipped with energy-dispersive spectrometers, which allowed the identification of chemical elements. The formation of chemical compounds Ni₄W and NiW₂ and nickel-tungsten solid solutions in regions along the initial nickel-tungsten interfaces was established. Decreasing values of the contact angles of wetting tungsten with nickel from ~15° to 4° with increasing temperature in the specified temperature range were observed. Penetration of molten nickel was detected along the interface between single crystals in the tungsten bicrystal, the content of which decreased from the surface of the sample in a quadratic dependence. The nature of the interaction of polycrystalline and bicrystal tungsten with molten nickel is practically identical. The obtained results can be used in the development of composite materials and alloys, including pseudoalloys, in determining the area of their use, as well as in optimizing the processes of soldering and obtaining nickel-containing coatings on refractory metals.