Micromechanical and structural properties of nickel coatings electrodeposited on two different substrates

Abstract

Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness.

Sitnozrne prevlake nikla su elektrodeponovane iz sulfamatnog kupatila na različitim supstratima: hladno-valjanom polikristalnom bakru i monokristalnom silicijumu (111) orijentacije. Uticaj supstrata i odabranih parametara elektrodepozicije na mehanička i strukturna svojstva ovih kompozitnih struktura ispitivan je testovima mikrotvrdoće po Vickers-u pri različitim opterećenjima. Iznad kritične dubine utiskivanja, izmerena vrednost tvrdoće nije tvrdoća elektrodeponovanog filma, već takozvana 'kompozitna mikrotvrdoća', jer supstrat učestvuje u plastičnoj deformaciji tokom procesa utiskivanja. Odabrana su dva modela kompozitne tvrdoće bazirana na različitim principima (model Chicot-Lesage i Korsunsky) i primenjena na eksperimentalne rezultate u cilju izračunavanja tvrdoće filma. Vrednosti mikrotvrdoće elektrodeponovanih prevlaka nikla zavise od vrednosti gustine struje. Povećanje gustine struje vodi smanjenju veličine zrna i povećanju vrednosti mikrotvrdoće.