Atomic Force Microscope Study of Friction at the Submicron-Scale During Tribotests With Self-Mated Steel

Abstract

Friction at the microscale during reciprocal sliding tribotests was studied for the first time with self-mated steel (100Cr6/AISI 52100) taking advantage of an atomic force microscope (AFM). To this aim, microsized steel particles were glued to the AFM-cantilever and employed as colloidal tips to perform tribotests on a steel disc. The torsion of the cantilever, which correlates with the friction force, was measured during the tests. Due to the irregular shape of the test particles and their wear, it is not possible to calibrate the torsional response of the cantilever and absolute quantification of the friction force cannot be achieved. Nevertheless, the model system used in the presented measurements is more representative of the tribology of real mechanical tribo-elements than already studied systems, in which for example only one tribopartner is worn. Few tests with the same load did not yield any wear and show that the load and adhesion contributions to friction stay constant when the shape of the test particle does not change. Most of the presented tribotests engendered wear. For those tests, the increase of friction during the tribotests was detected and was attributed to the emerging plowing contribution. Furthermore, analysis of both torsion and local slope experienced by the cantilever during the tests gives information on the creation of wear particles and their influence on friction.