Calculations of the impact of friction and wear on energy consumption, economic expenditure, and CO2 emissions are presented on a global scale. This impact study covers the four main energy consuming sectors: transportation, manufacturing, power generation, and residential. Previously published four case studies on passenger cars, trucks and buses, paper machines and the mining industry were included in our detailed calculations as reference data in our current analyses. The following can be concluded:

 Fifty years ago, wear and wear-related failures were a major concern for UK industry and their mitigation was considered to be the major contributor to potential economic savings by as much as 95% in ten years by the development and deployment of new tribological solutions. The corresponding estimated savings are today still of the same orders but the calculated contribution to cost reduction is about 74% by friction reduction and to 26% from better wear protection. Overall, wear appears to be more critical than friction as it may result in catastrophic failures and operational breakdowns that can adversely impact productivity and hence cost.

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Influence of tribology on global energy consumption, costs and emissions

The impact of tribology on energy use and CO2 emission globally and in combustion engine and electric cars

Global energy consumption due to friction and wear in the mining industry

The coefficient of friction (COF) of metals is usually high, primarily because frictional contacts induce plastic deformation underneath the wear surface, resulting in surface roughening and formation of delaminating tribolayers. Lowering the COF of metals is crucial for improving the reliability and efficiency of metal contacts in engineering applications but is technically challenging. Refining the metals' grains to nanoscale cannot reduce dry-sliding COFs, although their hardness may be elevated many times. We report that a submillimeter-thick stable gradient nanograined surface layer enables a significant reduction in the COF of a Cu alloy under high-load dry sliding, from 0.64 (coarse-grained samples) to 0.29, which is smaller than the COFs of many ceramics. The unprecedented stable low COF stems from effective suppression of sliding-induced surface roughening and formation of delaminating tribolayer, owing to the stable gradient nanostructures that can accommodate large plastic strains under repeated sliding for more than 30,000 cycles.

https://advances.sciencemag.org/content/advances/2/12/e1601942.full.pdf

Lowering coefficient of friction in Cu alloys with stable gradient nanostructures

This review focuses on the effect of metal-containing nanomaterials on tribological performance in oil lubrication. The basic data on nanolubricants based on nanoparticles of metals, metal oxides, metal sulfides, nanocomposities, and rare-earth compounds are generalized. The influence of nanoparticle size, morphology, surface functionalization, and concentration on friction and wear is analyzed. The lubrication mechanisms of nanolubricants are discussed. The problems and prospects for the development of metal-containing nanomaterials as lubricant additives are considered. The bibliography includes articles published during the last five years.

/pdf/metal-containing-nanomaterials-as-lubricant-additives-state-gp9jp9ii6w.pdf

Metal-containing nanomaterials as lubricant additives: State-of-the-art and future development

Mechanical wear and tear is a fact of life as old as tools themselves, yet is still not fully understood. Here large-scale atomistic simulations combined with atomic force microscopy provide a deep microscopic understanding of unconstrained surface plastic flow in polycrystalline metals. These findings suggest that engineering crystallographic surface texture to avoid formation of folds is a way forward in designing wear-resistant metal surfaces.

Origins of Folding Instabilities on Polycrystalline Metal Surfaces

Finely dispersed copper nanoparticles were added as an additive to fully-formulated engine oils. The copper additive was in colloidal form, with an inner core of Cu2+ atoms covered by surfactants to form stable reverse micelles that are completely dispersible in the base oil. The tribological process to form protective films at the metal surface is comprised of three phases. Phase I can be considered a physical process involving the build-up of polar molecules by absorption to produce a friction modifier film, whereas phases II and III have to be treated as mechanochemical processes comprising a combination of redox reactions and a third body formation. The tribological performance was investigated using atomic force microscopy, a microtribometer, a pin-on-disk tribometer in combination with continuous and high-resolution wear measurements with radionuclide technique, and high pressure stressing in a thrust roller bearing test rig. In addition, the nanostructure of the additive was characterized by atomic force microscopy. Finally, the chemical composition of the metal surface was analyzed using photoelectron spectroscopy.

https://www.mdpi.com/2075-4442/4/4/36/pdf

Multi-Phase Friction and Wear Reduction by Copper Nanopartices

The running-in corridor of lubricated metal–metal contacts

https://publikationen.bibliothek.kit.edu/1000119170/83326160

Surface engineering of a titanium alloy for tribological applications by nanosecond-pulsed laser

In this study, we evaluate the evolution of the interfacial processes in metallic sliding contacts (ie, 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 (ie, 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

Dominic Linsler

Papers

Origins of Folding Instabilities on Polycrystalline Metal Surfaces

Multi-Phase Friction and Wear Reduction by Copper Nanopartices

The running-in corridor of lubricated metal–metal contacts

Surface engineering of a titanium alloy for tribological applications by nanosecond-pulsed laser

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