engleski

Electrodeposition of nickel composite coatings with Al2O3 and TiO2

Composite coatings containing either alumina or titania particles in a nickel matrix were prepared by means of electrochemical deposition from nickel plating baths in which fine submicron size particles of -alumina (Buehler USA) or titania (Cinkarna Celje Slovenia) were kept suspended by mechanical stirring. Conventional nickel sulphate plating bath was used in all electroplating experiments. Coatings were prepared under constant stirring rate and temperature but at different current densities and different concentration of particles suspended in the bath. Deposition time was adjusted accordingly to the operating current to obtain an approximately constant coating thickness. Copper plates were used as a substrate for nickel composites coatings. Particles content in the composites was determined by dissolving of samples of coatings and analyzing the obtained solutions by AAS-ICP method. Optical and SEM microscopy were used in studying the surface morphology of coatings. The structure and mechanical properties of the composites were investigated as a function of applied current density and particles content in the coatings. The surface morphology and microstructure was significantly altered due to the particles embedded in the coatings. Metallographic analysis has shown a uniform particles distribution across the coating. Particles content significantly affects the microhardness of composites as well as the wear resistance. Coatings prepared from a particles-free bath served for comparison with composite ones.

electrodeposition of nickel; composite coatings; Al2O3; TiO2

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