The influence of soot and dispersant on ZDDP film thickness and friction

Ratoi, Monica; Castle, R.; Bovington, C. H.; Spikes, H. A.

doi:10.1002/ls.3010170103

Cited by 55 publications

(38 citation statements)

References 22 publications

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“…The film forms rapidly with rubbing, as indicated by the darkening of the interference images, and reaches a limiting value of ca 120 nm mean thickness after about 30 minutes rubbing. This behaviour is very similar to that seen previously with ZDDP solutions [1][27]. This film-forming behaviour was quite repeatable although the final film thickness formed varied slightly from between 100 and 120 nm from test to test.…”

Section: Removal Of Zddp Film By Carbon Blacksupporting

confidence: 88%

“…Over the years a number of different such mechanisms have been suggested, as indicated in Table 1, modified from [1]. Soot promotes oil degradation that in turn promotes wear [5].…”

Section: Introductionmentioning

confidence: 99%

“…The most widely supported mechanism of wear by soot, especially in recent years, is that soot abrades the antiwear films formed by ZDDP [1][15]- [17], [23]. These films, which are now recognised to be primarily amorphous zinc or calcium phosphate, are softer than steel and thus should be much more susceptible to abrasion by soot.…”

Section: Introductionmentioning

confidence: 99%

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Antagonistic Interaction of Antiwear Additives and Carbon Black

2009

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SUMMARYIt is well known that the presence of soot in engine oils can lead to an increase in wear of engine parts. This is a growing problem as soot levels in diesel engine oils are rising due to a combination of extended drain intervals and the various methods employed to reduce NOx formation such as retarded ignition and exhaust gas recirculation.Several different mechanisms have been proposed by which soot might lead to an increase in wear in mixed lubrication conditions, of which the most widely favoured is abrasion by soot, either of the rubbing metallic parts in engines or of the antiwear additive films formed on rubbing metal surfaces.In this study it is shown that the combination of mixed alkyl ZDDP and carbon black (used as soot surrogate) is strongly antagonistic in terms of wear. In a lubricant containing carbon black, the presence of ZDDP leads to considerably more wear than if ZDDP is left out. A similar, though less severe antagonism is also seen with primary ZDDP and other antiwear and EP additives. By varying the lubricant film thickness it is shown that the effect of carbon black in ZDDP-containing oils is to promote wear up to quite thick hydrodynamic film conditions, approaching the secondary carbon black particle size.It is proposed that the antagonistic wear effect results from a corrosion-abrasive mechanism in which the reaction film formed by antiwear additive and rubbing metal surface is very rapidly and continually abraded by carbon black. At most carbon black concentrations, wear rate then becomes controlled by the rate of initial antiwear additive film formation, which for secondary ZDDP is very rapid, rather than by the kinetics of the abrasive process.From this understanding, strategies for reducing the impact of engine soot on wear can be deduced.

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Section: Removal Of Zddp Film By Carbon Blacksupporting

confidence: 88%

“…Over the years a number of different such mechanisms have been suggested, as indicated in Table 1, modified from [1]. Soot promotes oil degradation that in turn promotes wear [5].…”

Section: Introductionmentioning

confidence: 99%

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Antagonistic Interaction of Antiwear Additives and Carbon Black

2009

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“…A similar mechanism of action is known to occur in the case of antiwear or extreme pressure additives (e.g. ZDDP) [28].…”

Section: Characterization Of Ws 2 Nanoadditive Tribofilmmentioning

confidence: 99%

“…u d )/2 (where u b and u d are the speed of the ball and the disc, with respect to the contact) was 150 %. This slideroll ratio value was selected to be higher than in previously reported research [28] to accelerate the generation of the chemically reacted tribofilm, which is known to depend on the severity of the rubbing conditions [29]. During the test, the NP dispersion was maintained at constant temperature in the enclosed, temperature-insulated chamber, where it was stirred continuously and vigorously by the circular movements of the disc and ball.…”

Section: Ws 2 Nanoadditive Tribological Performancementioning

confidence: 99%

Mechanism of Action of WS2 Lubricant Nanoadditives in High-Pressure Contacts

et al. 2013

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Because of their excellent tribological properties and potential to replace problematic lubricant additives currently in use, WS 2 nanoparticles have spurred considerable interest over the last two decades from academia and industry to decipher their mechanism of action. To elucidate the mechanism, this study carried out tribological tests at low and high temperatures and investigated the wear track and friction properties. It was found that in highpressure, high-temperature sliding contacts, WS 2 nanoadditives react with the metal substrate to generate thick chemical tribofilms which account for their excellent tribological properties. Based on XPS and FIB/SIMS results, a layered structure was proposed for the chemically formed tribofilms. The large amount of W in the composition of the reacted tribofilm could explain the excellent mechanical and antiwear properties, while the exfoliated squashed WS 2 NPs which fill the gaps and cover the reacted tribofilm account for the striking reduction in the boundary friction.

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Material‐Dependent Antagonistic Effects between Soot and ZDDP

Kumara

Meyer

2020

Adv Materials Inter

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While soot in engine oil is known to accelerate the wear of diesel and gasoline direct‐injection compression‐ignition engines, there is a lack of consensus on the wear mechanism though various hypotheses have been proposed in the literature. Particularly, some recently observed antagonistic effects between soot and a common lubricant antiwear additive, zinc dialkyldithiophosphate (ZDDP), while others did not. The discrepancy is, in part, explained by the strong alloy dependence of such antagonism discovered in this study. Four alloys, 52100 steel and M2, M50, and A2 tool steels, are tested in lubricants containing carbon black (CB, a soot surrogate) with and without ZDDP present. Adding the CB alone to the oil increases the wear rate for all steel alloys as expected. However, distinct wear performance is observed for the four steel alloys when ZDDP is introduced to the CB‐containing oil: while the 52100 steel has notable wear reduction, the three tool steels suffer significant wear increase. Comprehensive tribofilm characterization suggests that the Mo content in the steel alloy and the sulfur from ZDDP strongly influence wear behavior. The combination of CB/Mo‐catalyzed sulfidation and CB‐accelerated abrasion is hypothesized to be responsible for the high wear of the Mo‐alloyed tool steels.

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The influence of soot and dispersant on ZDDP film thickness and friction

Cited by 55 publications

References 22 publications

Antagonistic Interaction of Antiwear Additives and Carbon Black

Antagonistic Interaction of Antiwear Additives and Carbon Black

Mechanism of Action of WS2 Lubricant Nanoadditives in High-Pressure Contacts

Material‐Dependent Antagonistic Effects between Soot and ZDDP

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