INFLUENCE OF ELECTROLYSIS CONDITIONS ON THE COMPOSITION OF ELECTROLYTIC COMPOSITE COATINGS BASED ON COBALT

Abstract

The composite coatings electrodeposition with the refractory metals with cobalt makes it possible to obtain a coating with a unique combination of physicochemical properties that are unattainable when using other application methods. One of the reasons for the limited use of the electrolytic method of coating with such composites is the difficulty of controlling the process. The properties of alloys of the iron subgroup with refractory metals and composites depend not only on the chemical composition (the content of the refractory component) but also on the deposition conditions. By varying the composition of the electrolyte in galvanostatic mode it is impossible to obtain high-quality composite coatings with a high content of refractory components and current efficiency. As an alternative, it was suggested the use of pulsed electrolysis mode that allows to improve the producing of composite coatings. The process of formation of composite electrolytic coatings based on cobalt Co-W-ZrO2 on a copper substrate in pulse mode with a diphosphate-citrate electrolyte was investigated. The effect of current density, pulse duration and frequency on the coating composition, surface morphology, and current efficiency of compositional electrolytic coatings based on cobalt with refractory metals. An increase in current density causes a decrease in the content of refractory metals in compositional electrolytic coatings and an increase in oxygen content. The resulting coatings differ in a uniformly developed surface without cracks, which provides a sufficiently high adhesion. It is established that the size of the globe on the surface of the alloy decreases with increasing current density to 10 A/dm2. The control of the composition of Co-W-ZrO2 galvanic alloys in a quite wide range of alloying components concentrations is being achieved by varying the parameters of the pulse electrolysis, which allows adapting of the deposition technology to the needs of the modern market.