Indentation behaviour of 'soft film on hard substrate' composite system type

Abstract

This investigation has been carried out in order to analyse and compare the hardness response of different composite systems of the same type, named 'soft film on hard substrate' composite system. Composite systems of mono- and multilayered electrodeposited Ni and Cu thin films on (100) and (111)-oriented monocrystalline Si wafers and 100 µm-thick electrodeposited Ni film as the substrates were fabricated. The indentation behaviour of these composite structures was characterized using Berkovich nanohardness and Vickers microhardness testing. The measured hardness is so-called 'composite hardness', because the substrate participates in the plastic deformation during the indentation process. The contribution of the substrate to the measured hardness starts at indentation depths of the order of 0.07- 0.2 times the film thickness. Dependence of nanohardness and microhardness values on electrodeposition process conditions, substrate and film microstructure, total film thickness, layer thickness and Ni/Cu layer thickness ratio for different composite systems ratio was investigated. Composite hardness model of Chicot-Lesage (C-L) was chosen and applied to experimental data in order to determine absolute film hardness.