engleski

Surface Quality Measurement of Ni - Al2O3 Composite Coatings

Nickel composite coatings were prepared by electrochemical deposition of nickel from conventional nickel sulphate bath in which -Al2O3-nanoparticles were suspended. Composite coatings were obtained at different current densities and different concentration of suspended particles in the bath but at a constant temperature and stirring rate. Depositing time was estimated based on the applied current density to get coatings of approximately the same thickness. Copper plates were used as a substrate in preparing the composite coatings. Surface topography and the structure of coatings were then investigated by using optical and SEM microscopy as well as metallographic analysis of cross-sectional areas of coatings and by X-ray analysis. To get better insight of coating surface, amplitude surface roughness parameters as: Ra, Rp, Rv, Rz were determined, as well as hybrid roughness parameters like Rpk, Rvk, Abbott – Firestone curves, Mr1, Mr2 were also measured. As a referent sample for comparison coatings obtained from nickel bath without particles but at the same other experimental conditions were used. It was found that the embedded alumina particles significantly affect the surface morphology as well as microstructure of composite coatings. Increase of the particles captured in coating causes increase change of its properties. Obtained results have shown an increase in surface roughness parameters with increasing both depositing current density and alumina particles concentration in the bath. Produced composite coatings have had a relatively flat (smooth) surface area (a low fraction of peaks, parameter Mr1), but with a lot of dents on the surface area (high value of parameter Mr2). Also, the values of other measured surface roughness amplitude parameters as well as the Abbott-Firestone curves, confirmed this findings. Optical and SEM microscopy analysis supported results obtained by measuring the surface roughness parameters. X-ray analysis proved the presence of Al2O3 particles in the coatings while the metallographic analysis has shown uniform distribution of particles within the whole coating depth.

Al2O3-nanočestice; elektrokemijsko taloženje kompozitne prevlake nikla; optička i SEM mikroskopija; površinska hrapavost; površinska topografija

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