Effect of Temperature of Citrate Electrolyte on Properties of Co–W Coatings

Abstract

The influence of temperature on the properties of nanocrystalline Co–W coatings obtained from a citrate electrolyte at pH 6.7 and deposited under natural convection conditions was studied. The influence of the electrolyte temperature on the morphology, composition, structure, and roughness of coatings, as well as their corrosion and tribological properties, is demonstrated. It is shown that the structure of the coating can change from the X-ray amorphous to the crystalline one when the deposition temperature of the coating is increased to 90°С. The average value of the mass wear of Cо–W coatings formed at 80°С and measured under the linear friction condition of 0.08 mg is 62 times lower than that of a Cr coating (4.95 mg) and 84 times lower that at the surface of steel SK-5 (6.71 mg). When testing by the reciprocating wear method, the value of the volumetric wear of Co–W coatings obtained in the 50–70°С temperature range was 0.00109 mm³, which is 55 times lower than the wear value of a Cr coating (0.0596 mm³) and 41 times lower than that of the steel SK-5 surface (0.0449 mm³). The paper also shows a slight decrease in the currents of corrosion coatings and a decrease in the dispersion values of the corrosion potentials obtained after mechanical polishing of the surface of the coatings at temperatures in the range of 20–90°С. Under the corrosive effect of 3.5% sodium chloride, an increase in the deposition temperature of the coating is accompanied by a slight increase in the corrosion current.