Localised micro-hardness measurements with a combined scanning force microscope/nanoindentation system

Abstract

Thin-film coatings, modified surface layers and multiple phases are increasingly being used to improve the properties and functionality of engineering materials. Nanoindentation effectively meets the industrial need to measure hardness on a micro- and even nanometre scale and has proved its worth in caracterising the mechanical properties of surfaces, subsurface regions, interfaces, phases and grain boundaries in a quasi non-destructive way. The depth-sensing indentation method provides a means of evaluating the elastic and plastic deformations of the tested material, from which the hardness and the elastic modulus can be calculated. The combination of such an instrument with high resolution scanning force microscopy (SFM) and a conventional optical microscope provides a system capable of a more complete analysis of important surface parameters such as surface micro-roughness, topography and grain structure. In addition to the precise measurement of the indentation depth, the displaced material volume can also be measured together with other important information concerning the processes taking place on a microscale whilst performing such an indentation, e.g. plastic flow, micro-fracture, material compression and other interfacial effects. First results obtained on a multiphase high speed steel are presented, showing the net advantages of such a system in carrying out highly localised indentation studies together with precise measurement of imprints via SFM.