The characterization of near surface mechanical properties and the study of wear and friction behavior of materials is performed using the three-axial surface force apparatus developed in our laboratory.
Depth-sensing nanoindentation is coupled with surface imaging procedures performed with the same tip, which allows a precise choice of the indentation point before the test and then to measure the residual indent without moving the sample. Accurate stiffness measurements and precise contact area determination associated with an appropriate mechanical model give access to the elastoplastic properties of the material and to its structure (surface layers, film thickness).
With the same diamond tip, a new nano-machining procedure is used in order to remove the material from the surface to a pre-described depth. A succession of parallel scratches are made using both normal and tangential motion of the tip in the controlled displacement mode.
First this allows the creation of a new and flat area necessary for reliable nanoscale indentation and to access the mechanical properties at a given depth.
Second, as the friction and loading forces are recorded continuously during the process, the dissipated energy required to create the worn surface is measured. Information about wear and friction behavior of the surface can be obtained through this new development.