Nanotribology: Size-dependent friction coefficient and surface evolution
Wear and abrasion occur during sliding friction of metallic body and counter-body. Surface roughness is purposefully introduced into the metal to reduce wear and abrasion and to increase the lubricant flow.
As both bodies slide past each other, solid - solid micro-contacts develop because the lubricant only partially covers the surface in most applications.
To mimic the micro-contacts and the plastic micro-plowing during run-in, we use a diamond sphere as counter-body for the studied metals. During the deformation process, forces and displacements in the normal and tangential direction are recorded and this time-dependent data is analyzed using spectral analysis. Post-deformation measurements of the surface roughness by atom force microscopy (AFM) and confocal microscopy allow to determine the real contact area and the traces of the metal stick-slip behavior.
Images from the scanning electron microscope (SEM) show the microstructure evolution.