On the effect of surface topography and humidity on lubricated running-in of a carbon based coating

Svahn, Fredrik; Kassman-Rudolphi, Åsa; Hogmark, Sture

doi:10.1016/j.wear.2006.03.012

Cited by 11 publications

(6 citation statements)

References 9 publications

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“…At low pressures where no lubricant degeneration occurs, we still see a change in microstructure of the two sliding surfaces, however, no running-in in the sense of a decreasing friction coefficient. On the other hand, a drop in friction coefficient under lubrication conditions has been experimentally observed for amorphous hydrocarbons [42] and is typically believed to be related to a change in surface roughness and thus a smooth transition from boundary lubrication to mixed lubrication and finally to elastohydrodynamic behavior. Due to the confined nature of our simulation setup such a change cannot occur.…”

Section: Discussionmentioning

confidence: 99%

Atomistic Insights into the Running-in, Lubrication, and Failure of Hydrogenated Diamond-Like Carbon Coatings

2010

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The tribological performance of hydrogenated diamond-like carbon (DLC) coatings is studied by molecular dynamics simulations employing a screened reactive bond-order potential that has been adjusted to reliably describe bond-breaking under shear. Two types of DLC films are grown by CH2 deposition on an amorphous substrate with 45 and 60 eV impact energy resulting in 45 and 30% H content as well as 50 and 30% sp(3) hybridization of the final films, respectively. By combining two equivalent realizations for both impact energies, a hydrogen-depleted and a hydrogen-rich tribo-contact is formed and studied for a realistic sliding speed of 20 m s(-1) and loads of 1 and 5 GPa. While the hydrogen-rich system shows a pronounced drop of the friction coefficient for both loads, the hydrogen-depleted system exhibits such kind of running-in for 1 GPa, only. Chemical passivation of the DLC/DLC interface explains this running-in behavior. Fluctuations in the friction coefficient occurring at the higher load can be traced back to a cold welding of the DLC/DLC tribo-surfaces, leading to the formation of a transfer film (transferred from one DLC partner to the other) and the establishment of a new tribo-interface with a low friction coefficient. The presence of a hexadecane lubricant leads to low friction coefficients without any running-in for low loads. At 10 GPa load, the lubricant starts to degenerate resulting in enhanced friction

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Section: Discussionmentioning

confidence: 99%

Atomistic Insights into the Running-in, Lubrication, and Failure of Hydrogenated Diamond-Like Carbon Coatings

2010

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“…If the coating allows for a gentle running in wear of both the coating and the counter surface during early stages of use, where the most protruding asperities are worn down, it is however possible to achieve good adhesion and low wear, even on rough substrates [2].…”

Section: Introductionmentioning

confidence: 99%

Design of low-friction PVD coating systems with enhanced running-in performance — carbon overcoats on TaC/aC coatings

Nyberg

Tokoroyama

Wiklund

et al. 2013

Surface and Coatings Technology

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The widespread use of low friction PVD coatings on machine elements is limited by the high costs associated with fulfilling the demands on the surface quality of both the supporting substrate and the counter surface. In this work, an attempt is made at lowering these demands, by adding a sacrificial carbon overcoat to a TaC/aC low friction coating. Both coatings were deposited by planar magnetron DC sputtering, as separate steps in a single PVD-process.Coatings were deposited on substrates of two different surface roughnesses, in order to test the ability of this coating system to function on rougher substrates. Reciprocating ball on disc tests were performed, using balls with two different surface roughnesses. The worn surfaces were investigated using 3-D profilometry and SEM. The ability of the different overcoats to initially reduce the roughness of both the coated surface and the counter surface and to produce stable, low-friction conditions was examined for the different initial roughnesses. The implications for design of efficient run-in coatings for various systems are discussed.

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“…Observations of fatigue-like failure [19], friction and wear properties due to surface topography [27,28], and scuffing performance [29], for example, provided crucial information for understanding tribological behavior of layered materials.…”

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confidence: 99%

Stress Analysis on Layered Materials in Point Elastohydrodynamic-Lubricated Contacts

Wang

et al. 2009

Tribol Lett

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For multilayered or coated substrates in elastohydrodynamic-lubricated (EHL) contacts, the subsurface stress distributions under a normal load combined with shear traction have been analyzed in this article through computer simulations. The Papkovich-Neuber potentials and Fourier transform are adopted to deduce the pressuredisplacement, pressure-stress, and shear traction-stress response functions in frequency domain for the coated substrates, and to calculate distributions of pressure and subsurface stress. The results from the analysis of EHL contacts on coated substrates are compared with those from dry contact model in which shear traction is assumed to obey Coulomb's law. Effects of the Young's modulus of coatings, the properties of lubricants, and the magnitude of traction are discussed. Similar to the results in dry contacts, hard coatings in lubricated cases tend to increase the von Mises stress, whereas soft coatings decrease the stress. Shear traction makes the max von Mises stress increasing and moving closer to surface. However, the changes in subsurface stress due to shear traction are less obvious in lubricated contacts. Comparison between EHL and dry contact models reveals that lubrication can reduce the von Mises stress in the coating layer due to smaller shear traction. The analyses show that pressure, film thickness, and subsurface stress distributions are influenced by surface coatings, sliding velocity, rheological models, and pressure-viscosity behaviors.

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On the effect of surface topography and humidity on lubricated running-in of a carbon based coating

Cited by 11 publications

References 9 publications

Atomistic Insights into the Running-in, Lubrication, and Failure of Hydrogenated Diamond-Like Carbon Coatings

Atomistic Insights into the Running-in, Lubrication, and Failure of Hydrogenated Diamond-Like Carbon Coatings

Design of low-friction PVD coating systems with enhanced running-in performance — carbon overcoats on TaC/aC coatings

Stress Analysis on Layered Materials in Point Elastohydrodynamic-Lubricated Contacts

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