Abstract
The subject of the present paper is the characterization of third bodies of run-in systems. By means of continuous friction and wear measurement, lubricated steel-steel and steel-aluminum contacts were evaluated. Microstructure, chemical composition and response of the materials to shear were analyzed by XPS/AES and focused ion beam technique. After a proper running-in, both systems developed a third body. The third body differs significantly from the base materials. In addition to adapted microstructure and near-surface chemistry, the third body exhibited a substructure characterized by a near-surface zone that accommodates shear and a second, deeper region that ensures strengthening.
Highlights
As Dienwiebel et al showed for a lubricated chromium-cast iron contact with a contact pressure in the MPa range, that the question whether the film is on top or underneath can be answered by analyzing the energy consumption during film formation—very often during running-in—and by observing the changes of surface, microstructure and chemical composition of the near-surface as function of time [1]
The involved materials respond by changes in topography, changes in near-surface microstructure, phase transformation and modified chemical composition
The steel-steel system started with a coefficient of friction of 0.1 and showed good running-in behavior leading to a final coefficient of 0.02
Summary
As Dienwiebel et al showed for a lubricated chromium-cast iron contact with a contact pressure in the MPa range, that the question whether the film is on top or underneath can be answered by analyzing the energy consumption during film formation—very often during running-in—and by observing the changes of surface, microstructure and chemical composition of the near-surface as function of time [1]. For MPa systems in the initial stage of their running-in and highly-loaded contacts (GPa) like gears, the materials tend to develop protective films, commonly containing Zn, P and S from extreme pressure additives. The involved materials respond by changes in topography (dissipative structures [3], material transfer or film formation), changes in near-surface microstructure, phase transformation and modified chemical composition. Terms like tribologically transformed layer, reaction layer or tribomutation appeared, causing a great deal of confusion in the community
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