Friction of Clean Metals and the Influence of Surface Films

Bowden, F. P.; Hughes, T. P.

doi:10.1038/1421039b0

Cited by 12 publications

(10 citation statements)

References 5 publications

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“…Contrary to the centuries-old conventional wisdom that unlubricated self-mated pure metal contacts coldweld, gall and invariably produce high friction and wear [1][2][3][4][5][6][7], we present evidence that it is in fact possible to achieve low friction (with friction coefficients of µ < 0.5) with pure bare metals such as pure Cu and Au. There are rare instances in the literature where this behavior has been shown before without surface modifying films, most prominently in Prasad et al [8] for pure Ni and by Tamai for pure Cu and Au [9].…”

Section: Introductioncontrasting

confidence: 63%

Linking microstructural evolution and macro-scale friction behavior in metals

et al. 2016

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A correlation is established between the macro-scale friction regimes of metals and a transition between two dominant atomistic mechanisms of deformation. Metals tend to exhibit bi-stable friction behavior --low and converging or high and diverging. These general trends in behavior are shown to be largely explained using a simplified model based on grain size evolution, as a function of contact stress and temperature, and are demonstrated for pure copper and gold. Specifically, the low friction regime is linked to the formation of ultra-nanocrystalline surface films (10 to 20 nm), driving toward shear accommodation by grain boundary sliding. Above a critical combination of stress and temperature --demonstrated to be a material property --shear accommodation transitions to dislocation dominated plasticity and high friction. We utilize a combination of experimental and computational methods to develop and validate the proposed structure-property relationship. This quantitative framework provides a shift from phenomenological to mechanistic and predictive fundamental understanding of friction for crystalline materials, including engineering alloys.

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Section: Introductioncontrasting

confidence: 63%

Linking microstructural evolution and macro-scale friction behavior in metals

et al. 2016

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“…Although the kinetic friction is reduced by the primary film of oxygen it does not fall to the low values normally observed in air until comparatively thick layers of oxide are built up on the surface. A similar effect was observed with a fatty acid vapour (Bowden and Hughes 1938). The adsorp tion of a single layer of the vapour on the outgassed metal reduced the friction but it did not fall to the values usually observed for boundary lubricated surfaces (/i= 0*1-0*2) until a comparatively thic condensed on the surface.…”

Section: The Effect 0/ Surface Filmssupporting

confidence: 72%

“…A similar effect was observed with a fatty acid vapour (Bowden and Hughes 1938). The adsorp tion of a single layer of the vapour on the outgassed metal reduced the friction but it did not fall to the values usually observed for boundary lubricated surfaces (/i= 0*1-0*2) until a comparatively thic condensed on the surface.…”

Section: The Effect 0/ Surface Filmssupporting

confidence: 57%

The friction of clean metals and the influence of adsorbed gases. The temperature coefficient of friction

1939

Proc. R. Soc. Lond. A

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Experiments on electron diffraction and electron emission, as well as optical and other methods, have made it abundantly clear that, when a solid is cleaned in air by any ordinary method, its surface is still covered by a film of oxide, water vapour, and other adsorbed impurities. The surface film is often several molecular layers in thickness. Any complete theory of friction must take this film into consideration. Most experiments on the friction of metals are not made with metallic surfaces a t all, but with a metal coated with this surface film. If a lubricant is used it is not added to the metal directly, but is superimposed on the film of contaminant.Recent papers (Bowden and Leben 1939; Bowden and Tabor 1939) have described an investigation of the kinetic friction between unlubricated metal surfaces which had been cleaned in air. The experiments show th at sliding may not be continuous. The motion may proceed in jerks and large fluctuations may occur in the friction and in the surface temperature. The real area of contact between the metals is very small and corresponding fluctuations occur in it during sliding. The results suggest that metallic on May 11, 2018 http://rspa.royalsocietypublishing.org/ Downloaded from

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“…In general, it would be expected that bare metals brought into contact would cold-weld [7,8], leading to severe plastic deformation such as galling wear upon shearing [9,10]. However, as will be discussed in detail below, it is, in fact, possible to achieve low friction with bare metal sliding contacts, although the mechanisms behind this phenomenon were unclear until recently.…”

Section: Early Studies Of Metal Frictionmentioning

confidence: 99%

Friction of Metals: A Review of Microstructural Evolution and Nanoscale Phenomena in Shearing Contacts

Chandross

Argibay

2021

Tribol Lett

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The friction behavior of metals is directly linked to the mechanisms that accommodate deformation. We examine the links between mechanisms of strengthening, deformation, and the wide range of friction behaviors that are exhibited by shearing metal interfaces. Specifically, the focus is on understanding the shear strength of nanocrystalline and nanostructured metals, and conditions that lead to low friction coefficients. Grain boundary sliding and the breakdown of Hall–Petch strengthening at the shearing interface are found to generally and predictably explain the low friction of these materials. While the following is meant to serve as a general discussion of the strength of metals in the context of tribological applications, one important conclusion is that tribological research methods also provide opportunities for probing the fundamental properties and deformation mechanisms of metals.

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Friction of Clean Metals and the Influence of Surface Films

Cited by 12 publications

References 5 publications

Linking microstructural evolution and macro-scale friction behavior in metals

Linking microstructural evolution and macro-scale friction behavior in metals

The friction of clean metals and the influence of adsorbed gases. The temperature coefficient of friction

Friction of Metals: A Review of Microstructural Evolution and Nanoscale Phenomena in Shearing Contacts

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