Analysis of the composite and film hardness of electrodeposited nickel coatings on different substrates

Fine-grained nickel thin films were electrodeposited from a self-made sulphamate-based electrolyte on different substrates: polycrystalline cold-rolled copper and single crystal silicon with two different orientations, namely (100) and (111). The influence of the substrate and chosen plating conditions on mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called “composite hardness”, because the substrate also participates in the plastic deformations during the indentation process. Four composite hardness models (Jönsson–Hogmark, Burnett–Rickerby, Chicot–Lesage and Korsunsky models) are chosen and applied to the experimental data. The applicability of mentioned models is critically tested on two types of composite systems: Ni film on Cu substrate, which is example for “hard film on soft substrate” and electrodeposited Ni on Si substrate (“soft film on hard substrate”) and their reliability is given.