First Prize Mechanical Properties of Thin Films Quantified Via Instrumented Indentation

Abstract

Metallic coatings are primarily designed to enhance surface properties such as corrosion resistance, thermal protection, and tribological behaviour of a particular component in service. However, the deposition of such coatings inherently modifies the microstructure of the coating, resulting in mechanical properties of the coating that may differ significantly from those of the starting material from which the coating was produced. In addition, residual stresses are often present in the coating, and are strongly dependent upon deposition method and coating thickness. These stresses can lead to failure of the component owing to through-thickness cracking or interface delamination. Thus, it is clear that in order to maximise coating performance, the mechanical properties and stress state of the coating must be well characterised. Instrumented depth sensing indentation provides a means of quantifying the mechanical behaviour of the coated component on various size scales, depending on the maximum depth of the indentation. In addition, once mechanical properties have been ascertained via indentation, this method can also serve as a non-destructive quality control test during production. In the present work experimental and computational studies of micro- and nanoindentation on monolithic and coated metallic systems, including structural engineering alloys and microelectronic thin films, are described. The effects of material anisotropy, crystallographic orientation, and film thickness on the indentation response are consid ered, and these are correlated with the mechanical properties and residual stress state of the various systems.