Influence of tip adhesion on nanoindentation and scratching

Using molecular dynamics simulation, we study the influence of tip adhesion on nanoindentation and scratching. By using a model pair potential between tip atoms and substrate atoms, we can arbitrarily change the adhesion strength. For the prototypical case of a diamond tip and a bcc Fe substrate, we find that with increasing adhesion strength, the indentation hardness and also the normal hardness during scratching decreases. Even more pronounced is a strong increase of the transverse force and hence of the friction coefficient during scratching. The indent pit becomes atomically rough, and the pileup produced during scratch increases with increasing adhesion strength. On the other hand, the length of the dislocations produced and the spatial extent of the plastic zone shrinks. (paper)