Rezumat
CZU 541.138.2+621.9.047.7
The gluconate-based electrolyte was used for the electrodeposition of nanocrystalline Co-W coatings. A major influence of pH on the deposition rate, alloys content and structure, their microhardness and tribological properties is shown. It is supposed that coating characteristics are formed under the influence of high-molecular Co-gluconate and Cо-W-gluconate complexes generated in the electrolyte depending on the solution рН. The рН of 6–7 is found to be optimal for obtaining best coatings characteristics. Higher values (рН 8) cause the increase of the molecular weight of formed complexes from which sedimentation occurs. As a consequence, electrodeposition parameters and physicomechanical properties of coatings deteriorate. At lower рН values (pH 4–5) the tungsten content in the deposit decreases because of a higher rate of cobalt reduction from the Co-gluconate complex.
Keywords: Co-W alloys, nanocrystalline coatings, electrodeposition, heterometalic complexes, microhardness, friction and surface deterioration.