Does the Use of Diamond‐Like Carbon Coating and Organophosphate Lubricant Additive Together Cause Excessive Tribochemical Material Removal?

Zhou, Yan; Leonard, Donovan N.; Meyer, Harry M.; Luo, Huimin; Qu, Jun

doi:10.1002/admi.201500213

Cited by 16 publications

(20 citation statements)

References 23 publications

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“…1b , the cross-sectional STEM images clearly present an amorphous tribofilm of 50 nm thick, and in some conditions, with a porous top layer composed of very fine nanoparticles. EDS elemental mapping suggests that the tribofilm is rich in Fe, O, and P, indicating a composite of iron oxides and iron phosphates based on the previous chemical analysis 21 , 27 – 29 . A good bonding between the substrate and the bulk of a tribofilm is essential for its growth.…”

Section: Resultsmentioning

confidence: 80%

Understanding Tribofilm Formation Mechanisms in Ionic Liquid Lubrication

Zhou

Leonard

Guo

et al. 2017

Sci Rep

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Ionic liquids (ILs) have recently been developed as a novel class of lubricant anti-wear (AW) additives, but the formation mechanism of their wear protective tribofilms is not yet well understood. Unlike the conventional metal-containing AW additives that self-react to grow a tribofilm, the metal-free ILs require a supplier of metal cations in the tribofilm growth. The two apparent sources of metal cations are the contact surface and the wear debris, and the latter contains important ‘historical’ interface information but often is overlooked. We correlated the morphological and compositional characteristics of tribofilms and wear debris from an IL-lubricated steel–steel contact. A complete multi-step formation mechanism is proposed for the tribofilm of metal-free AW additives, including direct tribochemical reactions between the metallic contact surface with oxygen to form an oxide interlayer, wear debris generation and breakdown, tribofilm growth via mechanical deposition, chemical deposition, and oxygen diffusion.

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Section: Resultsmentioning

confidence: 80%

Understanding Tribofilm Formation Mechanisms in Ionic Liquid Lubrication

Zhou

Leonard

Guo

et al. 2017

Sci Rep

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“…The tribofilm thickness reaches 120 nm for G‐B and G‐E as compared to that derived from graphene‐free engine oil (50 nm). Based on the study of Zhou et al, GNP may have an effect to ZDDP tribofilm formation. This effect is predicted that accelerate the chemical reaction between ZDDP and steel substrate.…”

Section: Discussionmentioning

confidence: 99%

“…The presence of carbonaceous materials, e.g., carbon soot, at the sliding interface exerts a remarkable influence on the resulting friction and wear. Zhou et al proposed that diamond‐like carbon can provide a catalytic effect enhancing ZDDP tribofilm formation, in which the tribochemical reactions between the ZDDP additive and the steel surface are accelerated by carbon species …”

Section: Introductionmentioning

confidence: 99%

Unusual Competitive and Synergistic Effects of Graphite Nanoplates in Engine Oil on the Tribofilm Formation

Pham

Wan

Tieu

et al. 2019

Adv Materials Inter

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To exploit the improved efficiency from formulated oil modified with graphite nanoplates (GNP), it is important to understand how GNP behave alongside conventional additives such as zinc dialkyl dithiophosphates (ZDDP). The results in this work demonstrate unusual tribological responses of engine oil due to GNP additions, which cannot be explained by the traditionally low shearing mechanism between graphene layers in GNP. A competitive and synergistic effect of GNP on tribofilm formation is proposed for this unusual friction and wear behavior. The presence of GNP modifies the tribofilm formation and spontaneously creates alternate hard and soft regions from the microscopic view of the surface. At low concentrations (≤0.05 wt%), graphene is formed by shear‐assisted exfoliation of GNP and intermixed with intermediate oxide region. Due to its random orientation, graphene produces mechanical reinforcement of the tribofilm, but low shear yielding is not achieved. This gives rise to high friction but low wear conditions. At higher concentrations (>0.05 wt%), GNP align with their hexagonal sheets parallel to the surface to promote low‐shear sliding, but wear increases. This is due to GNP clumping together which makes them less effective at forming graphene and providing stable reinforcement of the tribofilm.

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“…Although tribofilms readily form on CrN, increasing friction occurs as well as an acceleration of wear on the opposing surface. In contrast, DLC/steel contacts result in superior tribological performance even in dry sliding conditions 1 , 2 , 7 – 10 . This is reported to be due to a nano-scale tribofilm with a predominantly sp 2 -type carbon surface which confers self-lubricating capability.…”

Section: Introductionmentioning

confidence: 97%

“…Intensive work has been carried out to evaluate the interactions between non-ferrous coatings and lubricant additives with regard to wear and friction plus the interfacial chemistry of the tribofilm, e.g. the CrN/steel and DLC/steel contacts 7 – 10 . For CrN/steel contacts, additive concentrations and additive types as well as the contacting conditions determine the friction and wear properties.…”

Section: Introductionmentioning

confidence: 99%

Tribochemistry of adaptive integrated interfaces at boundary lubricated contacts

Wan

Xia

Wang

et al. 2017

Sci Rep

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Understanding how an adaptive integrated interface between lubricant additives and solid contacts works will enable improving the wear and friction of moving engine components. This work represents the comprehensive characterization of compositional and structural orientation at the sliding interface from the perspective of surface/interface tribochemistry. The integrated interface of a lubricant additive-solid resulting from the friction testing of Graphite-like carbon (GLC) and PVD-CrN coated rings sliding against cast iron under boundary lubrication was studied. The results indicate that in the case of the CrN/cast iron pair the antiwear and friction behavior were very strongly dependent upon lubricant. In contrast, the tribology of the GLC surface showed a much lower dependence on lubrication. In order to identify the compounds and their distribution across the interface, x-ray microanalysis phase mapping was innovatively applied and the principle of hard and soft acids and bases (HSAB) to understand the behaviour. Phase mapping clearly showed the hierarchical interface of the zinc-iron polyphosphate tribofilm for various sliding pairs and different sliding durations. This interface structure formed between lubricant additives and the sliding surfaces adapts to the sliding conditions – the term adaptive interface. The current results help explain the tribology of these sliding components in engine.

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Does the Use of Diamond‐Like Carbon Coating and Organophosphate Lubricant Additive Together Cause Excessive Tribochemical Material Removal?

Cited by 16 publications

References 23 publications

Understanding Tribofilm Formation Mechanisms in Ionic Liquid Lubrication

Understanding Tribofilm Formation Mechanisms in Ionic Liquid Lubrication

Unusual Competitive and Synergistic Effects of Graphite Nanoplates in Engine Oil on the Tribofilm Formation

Tribochemistry of adaptive integrated interfaces at boundary lubricated contacts

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