Combination of DLC coatings and EP additives for improved tribological behaviour of boundary lubricated surfaces

Podgornik, Bojan; Hren, D.; Vižintin, J.; Jacobson, Staffan; Stavlid, Nils; Hogmark, Sture

doi:10.1016/j.wear.2005.09.007

Cited by 64 publications

(38 citation statements)

References 22 publications

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“…In agreement with previous investigations, [5,6,11,12] tribofilm formation coincided with further reduction in friction and was found to consist of transferred coating material (WC) and reaction products from the S-based additive (S). However, for the low additive concentration of 0.1%, WS-type tribofilm and friction of about 0.15 was maintained only for the first 10 000-20 000 sliding cycles.…”

Section: Surface Analysissupporting

confidence: 91%

“…As reported elsewhere [2,6,11,12] no reaction products or tribofilms were detected on W-DLC coatings. However, tribofilms formed on the steel counter-surface or on the exposed steel substrate were additive type and concentration, and contact conditions dependent.…”

Section: Surface Analysissupporting

confidence: 77%

“…However, even at 2.5 and 5% EP additive concentrations, a certain number of cycles were needed before low-friction behaviour with a coefficient of friction as low as 0.1 was reached. [11,12] The influence of the AW additive on frictional behaviour of W-DLC coatings running against steel was not so pronounced as it was for the EP additive. As shown in Fig.…”

Section: Resultsmentioning

confidence: 96%

“…Only a WC-type transfer layer was formed on the contact surface of the steel ball, which was responsible for the reduction of friction as compared to the steel/steel combination. [11,12] The absence of additive reaction products can be explained by the formation of a carbon transfer layer, which through reduced friction reduces contact temperatures [13] and inhibits reaction of EP additive with the steel surface. [4] In the case of AW additive concentrations above 1.0%, the AW additive reacts with the surface of the uncoated steel ball, forming the same phosphorus-rich tribofilm and giving the same friction (∼0.2) as observed for the steel/steel combination.…”

Section: Surface Analysismentioning

confidence: 99%

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Tribologically activated surface layers in lubricated DLC contacts

Podgornik

Vižintin

2008

Surface & Interface Analysis

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In the past, adequate functionality of high-performance components would have been impossible without advanced lubricant additive chemistry and proper lubricant formulation. Especially anti-wear (AW) and extreme-pressure (EP) additives are crucial in minimising friction and wear and protecting contact surfaces under severe contact conditions. Introduction of diamond-like carbon (DLC) coatings, on the other hand, opens further possibilities in improving performance of highly loaded components, which can no longer be achieved only by lubricant design.The aim of the present research was to determine the mechanism responsible for the low-friction behaviour of boundary lubricated DLC coatings when lubricated with lubricants containing EP or AW additives and to investigate the influence of contact conditions. Tests were performed under reciprocating sliding motion using ball on flat test configuration, with ball-bearing steel ball being loaded against undoped and W-doped DLC-coated discs, respectively. Results of the investigation clearly show that in the case of W-doped DLC coatings, low-friction behaviour under boundary lubrication is governed by formation of WS 2 -containing tribolayers, which are contact conditions dependent and can reduce friction by more than 50%.

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Section: Surface Analysissupporting

confidence: 91%

Section: Surface Analysissupporting

confidence: 77%

Section: Resultsmentioning

confidence: 96%

Section: Surface Analysismentioning

confidence: 99%

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Tribologically activated surface layers in lubricated DLC contacts

Podgornik

Vižintin

2008

Surface & Interface Analysis

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“…Film formation on the DLC disk occurred during the running-in process [44]. It is reported that tungsten in the transferred layer reacts with sulfur in the additive, forming lamellar WS 2 tribofilms [45]. Doping a reactive material, such as tungsten, with an additive seems to be effective in tribofilm formation.…”

Section: Formation Of Tribofilm = Not Detectedmentioning

confidence: 99%

Reducing Friction and Wear of Tribological Systems through Hybrid Tribofilm Consisting of Coating and Lubricants

2014

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Abstract:The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. However, there are limitations about the regeneration of the protecting film when additives are totally consumed. On the other hand, there are a lot of hard coatings to protect the steel surface from wear. These can enable the functioning of tribological systems, even in adverse lubrication conditions. However, hard coatings usually make the friction coefficient higher, because of their high interfacial shear strength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its relatively low friction and superior wear resistance. In practice, conventional lubricants that are essentially formulated for a steel/steel surface are still used for lubricating machine component surfaces provided with protective coatings, such as DLCs, despite the fact that the surface properties of coatings are quite different from those of steel. It is therefore important that the design of additive molecules and their interaction with coatings should be re-considered. The main aim of this paper is to discuss the DLC and the additive combination that enable tribofilm formation and effective lubrication of tribological systems.

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Modeling of the plasmonic properties of DLC‐Ag nanocomposite films

Yaremchuk

Tamulevičienė

Tamulevičius

et al. 2013

Physica Status Solidi (a)

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In this work we present results of theoretical and experimental investigation of the optical absorption spectra of thin films of nanocomposite materials composed of silver nanoparticles embedded in a diamond‐like carbon (DLC) matrix. The optical characteristics of DLC‐Ag nanocomposite are considered within the framework of the effective medium approximation. The evolution of plasmon resonance characteristics and optical properties due to changes of dielectric constant of DLC host and size of the embedded metal nanoparticles is studied. The experimental absorption spectra of DLC‐based silver nanocomposites deposited by reactive magnetron sputtering on fused‐silica were compared with the simulated ones. The observed redshift and broadening of the surface plasmon resonance (SPR) bands were explained using Mie scattering theory and Maxwell–Garnett effective medium theory. The obtained results suggest that a random mixture consisting of the DLC film with embedded isolated silver inclusions is a promising material for the fabrication of tunable nanocomposites in different sensing platforms.

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Combination of DLC coatings and EP additives for improved tribological behaviour of boundary lubricated surfaces

Cited by 64 publications

References 22 publications

Tribologically activated surface layers in lubricated DLC contacts

Tribologically activated surface layers in lubricated DLC contacts

Reducing Friction and Wear of Tribological Systems through Hybrid Tribofilm Consisting of Coating and Lubricants

Modeling of the plasmonic properties of DLC‐Ag nanocomposite films

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