Dependence of tribofilm characteristics on the running-in behavior of aluminum–silicon alloys

Abstract

In this study, we evaluate the evolution of the interfacial processes in metallic sliding contacts (i.e., aluminum alloys) in terms of their elemental composition, structural changes, and nanomechanical properties in order to understand the optimal running-in behavior leading to steady-state low friction and high wear resistance. Two different sliding conditions are used, resulting in low and high long-term friction and corresponding well with the low and high wear rates. Ex situ elemental analysis of these sliding experiments was performed by means of X-ray photoelectron spectroscopy. The mechanical properties were evaluated using nanoindentation and microcompression testing. While the elemental analysis revealed an increased oxide content for the near-surface region of the worn surfaces compared to the unworn material, the oxide content was higher for the experiments that resulted in an unfavorable tribological response (i.e., high friction and high wear). Similarly, the sub-surface grain-refined layer under these conditions was thicker compared to the experiment with a short running-in stage and low steady-state friction and wear. These observations correlated well with the nanoindentation and microcompression results, which show higher hardness and yield stress for the high friction and wear experiment. Correspondingly, low steady-state friction and wear were obtained with the formation of a thin and mechanically stable tribolayer.

Extreme shear-deformation-induced modification of defect structures and hierarchical microstructure in an Al–Si alloy

“…A nano indention hardness mapping was also performed which does not show conclusive trends as the alloy consists of a dual phase microstructure with very different hardness values of each phase and therefore the scatter in the hardness in the base material is very high, which makes it difficult to observe the trend in the hardness change due to deformation. A very high scatter was also observed by Stoyanov et al 41 . Stoyanov et al observed the change in nanomechanical properties of the shear deformed layer by tribometer as a function of contact pressure and observed that the lower pressure (15 MPa) showed a much higher degree of mechanical mixing and grain refinement compared to the higher pressure of 35 MPa in Al-Si alloy 41 .…”

“…A very high scatter was also observed by Stoyanov et al 41 . Stoyanov et al observed the change in nanomechanical properties of the shear deformed layer by tribometer as a function of contact pressure and observed that the lower pressure (15 MPa) showed a much higher degree of mechanical mixing and grain refinement compared to the higher pressure of 35 MPa in Al-Si alloy 41 .…”

Scaling Effects on Materials Tribology: From Macro to Micro Scale

“…The rheology and flows of the third bodies for macroscopic tribology has been described in detail by Descartes et al [ 44 ] and subsequently applied in other tribological systems [ 45 , 46 ]. The authors describe the source flow of the third body (i.e., material trapped in-between the first bodies, not including the ‘structural tribological transformation’ or thermal tribological transformation’ zone) in a natural and artificial form, being formed from an internal and an external source respectively.…”

Running-in for Low Friction between Silicon-Containing Aluminum Alloy and Bearing Steel in Engine Oil

“…Some authors have reported that the friction and wear properties of silicon-containing aluminum alloys improve through the reduction of friction and/or wear, known as running-in [23,26]. For example, Shioda et al [23] reported that by controlling the size and area ratio of the silicon grains, the friction system between bearing steel (AISI52100) and siliconcontaining aluminum alloy could exhibit running-in without an increase in the silicon content.…”