Combining scanning force microscopy with nanoindentation for more complete characterisation of bulk and coated materials

Abstract

The mechanical properties of thin films as well as bulk materials can be measured by a variety of different techniques, with nanoindentation being one of the most recent developments in this growing field. By using a depth-sensing indentation method it is possible to obtain quantitative values for the hardness and modulus, and thus gain better insight into the response of a material to controlled deformation at such small scales. However, the calculation of such values from conventional load-displacement curves can prove inaccurate owing to the effects of pile-up and sink-in which invariably occur during the indentation of many types of material and which seriously affect the calculation of residual contact area. This paper addresses the problem and suggests the use of scanning force microscopy (SFM) as a complimentary tool which allows the true residual contact area to be measured. In addition, some experimental results are presented for a variety of bulk and coated materials, these confirming the use of the SFM for obtaining significant additional information concerning the true response of a material to instrumented indentation at a nanometric scale, e.g., elastic/plastic deformation, cracking, phase transformation, pile-up/sink-in effects, etc.