Wear, friction and sliding speed correlations on Langmuir-Blodgett-films observed by atomic force microscopy

The dependence of friction and wear on sliding parameters has been investigated with an atomic force microscope. Measurements have been performed on Langmuir-Blodgett monolayers. For the purpose of this study a special counterion polymer has been used to supply a facile insight into the friction and wear dependence on the scan velocity. With a minimum constant load in the order of 10(-8) N, wear has been observed to occur randomly at film defect sites but also on initially intact film areas. Wear is always accompanied by an increase of friction forces. A wearless friction dependence on the scan velocity could not be observed. The process of wear is discussed in terms of shear forces and adhesive contact forces. Whereas the plastic deformation at the film defect sites can be explained by shear forces, the wear process on initially defect free surfaces could be related to adhesive forces and quantified.