Electrodeposition of high-tungsten W-Ni-Cu alloys. Impact of copper on deposition process and coating structure

A simple method of electrodeposition of a new class of materials – W-Ni-Cu alloys – has been proposed. The mean tungsten content was higher than 20 at.% which is a substantial increase compared to other reported in the literature values: 5–10 at.%. The major influencing factors of the plating process were identified and examined. This allowed us to settle the conditions for deposition of various W-Ni-Cu materials. These ternary alloys can be deposited from aqueous citrate solutions by employing the appropriate ratio of concentrations of W, Ni and Cu in the bath. The galvanic bath used for the electroplating is environmentally friendly and of low toxicity. The deposits are metallic, uniform, shiny and highly adhesive to various substrates. The layers colour, depending on copper percentage, can vary from dark silvery to bright silver-orange. Also, various mechanical properties of the deposits can be obtained by properly adjusting bath composition and therefore layer stoichiometry. The internal structure of the deposits was investigated and it was found that the size of structurally organized regions was circa 3–5 nm. The obtained material consists of two phases: a) nanocrystaline of a structure similar to cupronickel with decreased percentage of W and b) fully amorphous phase/matrix containing higher, than the mean value, percentage of W. The galvanic W-Ni-Cu layers did not exhibit preferred orientation in the [111] direction which is typical for the binary tungsten – iron-group-metal electrodeposited alloys.