Study of the mechanical properties of single- layer and multi-layer metallic coatings with protective-decorative applications

¹ Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl.4, 1113 Sofia, Bulgaria
² Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl.11, 1113 Sofia, Bulgaria

^* Corresponding author: sabina_cherneva@yahoo.com

Abstract

Single thin coating of matt nickel (N_imat), a mirror bright copper (Cu_bright), a mirror bright nickel (Ni_bright) and their combinations were electrochemically deposited on brass substrate with thickness 500 μm. The basic aim was electrodeposition of two-layer Cu_bright/N_imat and Ni_bright/Cu_bright systems, and three-layer Ni_bright Cu_brigh/N_imat system, which are among the most widely applied protective and decorative systems in light and medium operating conditions of corrosion. The thicknesses of the obtained films varied from 1 μm to 3.25 μm. They were investigated via nanoindentation experiments, in order to characterize their basic physical and mechanical characteristics, related with their good adhesion and corrosion protective ability, as well as ensuring the integrity of the system “protective coating/substrate” to possible mechanical, dynamic and/or thermal stresses. As a result, load-displacement curves were obtained and indentation hardness and indentation modulus were calculated using the Oliver & Pharr approximation method. The dependence of the indentation modulus and the indentation hardness on the depth of the indentation, surface morphology and structure of the obtained coatings, their texture and surface roughness were investigated too. The obtained results showed that the three-layer Ni_bright/Cu_bright /Ni_imat/CuZn37 system has highest indentation modulus and indentation hardness, following by two-layer Ni_bright/Cu_bright system and single layer coatings.