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16 pages, 4630 KiB

Open AccessArticle

Effect of Temperature on the Deformation Behavior of Copper Nickel Alloys under Sliding

by Stefan J. Eder, Philipp G. Grützmacher, Manel Rodríguez Ripoll, Daniele Dini and Carsten Gachot

Materials 2021, 14(1), 60; https://doi.org/10.3390/ma14010060 - 25 Dec 2020

Cited by 23 | Viewed by 3757

The microstructural evolution in the near-surface regions of a dry sliding interface has considerable influence on its tribological behavior and is driven mainly by mechanical energy and heat. In this work, we use large-scale molecular dynamics simulations to study the effect of temperature on the deformation response of FCC CuNi alloys of several compositions under various normal pressures. The microstructural evolution below the surface, marked by mechanisms spanning grain refinement, grain coarsening, twinning, and shear layer formation, is discussed in depth. The observed results are complemented by a rigorous analysis of the dislocation activity near the sliding interface. Moreover, we define key quantities corresponding to deformation mechanisms and analyze the time-independent differences between 300 K and 600 K for all simulated compositions and normal pressures. Raising the Ni content or reducing the temperature increases the energy barrier to activate dislocation activity or promote plasticity overall, thus increasing the threshold stress required for the transition to the next deformation regime. Repeated distillation of our quantitative analysis and successive elimination of spatial and time dimensions from the data allows us to produce a 3D map of the dominating deformation mechanism regimes for CuNi alloys as a function of composition, normal pressure, and homologous temperature. Full article

(This article belongs to the Special Issue Advances in Computational Materials Tribology)

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42 pages, 9323 KiB

Open AccessFeature PaperReview

Multi-Scale Surface Texturing in Tribology—Current Knowledge and Future Perspectives

by Philipp G. Grützmacher, Francisco J. Profito and Andreas Rosenkranz

Lubricants 2019, 7(11), 95; https://doi.org/10.3390/lubricants7110095 - 28 Oct 2019

Cited by 187 | Viewed by 13803

Abstract

Surface texturing has been frequently used for tribological purposes in the last three decades due to its great potential to reduce friction and wear. Although biological systems advocate the use of hierarchical, multi-scale surface textures, most of the published experimental and numerical works have mainly addressed effects induced by single-scale surface textures. Therefore, it can be assumed that the potential of multi-scale surface texturing to further optimize friction and wear is underexplored. The aim of this review article is to shed some light on the current knowledge in the field of multi-scale surface textures applied to tribological systems from an experimental and numerical point of view. Initially, fabrication techniques with their respective advantages and disadvantages regarding the ability to create multi-scale surface textures are summarized. Afterwards, the existing state-of-the-art regarding experimental work performed to explore the potential, as well as the underlying effects of multi-scale textures under dry and lubricated conditions, is presented. Subsequently, numerical approaches to predict the behavior of multi-scale surface texturing under lubricated conditions are elucidated. Finally, the existing knowledge and hypotheses about the underlying driven mechanisms responsible for the improved tribological performance of multi-scale textures are summarized, and future trends in this research direction are emphasized. Full article

(This article belongs to the Special Issue Laser-Induced Periodic Surface Nano- and Microstructures for Tribological Applications)

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14 pages, 3866 KiB

Open AccessArticle

Low Friction and High Solid-Solid Contact Ratio—A Contradiction for Laser-Patterned Surfaces?

by Simon Bettscheider, Philipp G. Grützmacher and Andreas Rosenkranz

Lubricants 2017, 5(3), 35; https://doi.org/10.3390/lubricants5030035 - 26 Aug 2017

Cited by 2 | Viewed by 5512

Abstract

Recording of Stribeck-like curves is a common way to study the effect of laser-patterned surfaces on the frictional efficiency. However, solely relying on the coefficient of friction when identifying the lubrication regime and the underlying working principles can be misleading. Consequently, a ball-on-disc tribometer was combined with an electrical resistivity circuit to simultaneously measure Stribeck-like curves and solid-solid contact ratios for polished and laser-patterned samples. Line-like surface patterns with different periodicities were produced by direct laser interference patterning on steel substrates (AISI304). The reference shows a Stribeck-like behavior well correlating with the contact ratios. The behavior deviates for high sliding velocities (high contact ratios) due to a loss of lubricant induced by centrifugal forces pulling the lubricant out of the contact zone. In contrast, the solid–solid contact ratio of the laser-patterned samples is around 80% for all sliding velocities. Those values can be explained by higher contact pressures and the structural depth induced by the surface topography which make a full separation of the surfaces unlikely. Despite those high values for the contact ratio, laser-patterning significantly reduces friction, which can be traced back to a reduced real contact area and the ability to store oil in the contact zone. Full article

(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)

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