Structural Features of Ni–W Alloy Deposited from Pyrophosphate Electrolyte

Abstract

The composition and structure of Ni–W alloys prepapred from pyrophosphate electrolyte have been studied. It was demionstrated that, regardless of the deposition current density in the range 2–5 A dm–2, alloys are a single-phase system and represent a solid solution of tungsten in nickel with a face-centered cubic lattice. At low deposition current densities in the coating there exists an impurity oxygen-containing phase of tungsten compounds of an intermediate oxidation state. It was found that the oxygen-containing impurity is distributed unevenly over the coating thickness. Impurity grains are formed only at the initial moment of deposition of the coating at the interface with the substrate together with nickel nanocrystals, and only after some time does the formation of the alloy phase begin. The data obtained are explained in term of the cluster mechanism of induced coprecipitation of alloys of refractory metals with metals of the iron group, proposed earlier.