A study of copper coatings electrodeposited in electrolyte with a metallic powder of chromium

Abstract

Copper coatings modified with chromium and sulfur inclusions were electrodeposited in acidic copper sulfate electrolytes containing a metallic powder of chromium. It was found that a metallic powder of chromium is not suitable to obtain Cu–Cr composites in contrast to chemical inert particles of other non-metallic powders. Due to electrochemical reduction of partially dissolved chromium ions it is rather an “alloying precursor with chromium” of a fine-textured Cu–Cr matrix. The aim of this paper was to present the data on investigations of the morphology of formed new materials and functionality based on their mechanical properties (hardness, wear resistance), electrical resistivity and thermal stability of smooth-faced copper coatings with chromium and sulfur inclusions as compared with those of crystalline surface of pure copper matrix. With respect to increase in the smoothness of coating surface the hardness (HV 50) increases from 180 to 240 kgf mm − 2 , and shows a significantly higher wear resistance and more intensive phase transformations of Cu–Cr–S coating surface at higher temperatures in nitrogen atmosphere. Meta-stable phases of CuS were formed at temperatures higher than 200 °C and Cr 2N or CrN higher than 600 °C, which may be a stabilized matrix of copper coating in nitrogen atmosphere in contrast to an oxidative degradation of copper coatings in oxygen-containing atmosphere at higher temperatures. The electrical resistivity being the basic functional property of the formed Cu–Cr–S coating is similar to that of pure copper coating. The increase in temperature from − 150 to 100 °C results in increase in resistivity of copper materials from 1.2 to 2.8 × 10 − 8 Ω m for pure copper and from 0.8 and 0.6 to 2.6 and 2.1 × 10 − 8 Ω m for Cu–Cr–S coatings.