Synergistic effect on frictional characteristics under rolling-sliding conditions due to a combination of molybdenum dialkyldithiocarbamate and zinc dialkyldithiophosphate

Muraki, Masayoshi; Yanagi, Yoshihiro; Sakaguchi, Kei

doi:10.1016/0301-679x(96)00025-4

Cited by 90 publications

(69 citation statements)

References 14 publications

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“…Using high resolution TEM observations of wear debris, coupled with wear scar micro-spot XPS analysis, they observed perfectly oriented MoS 2 sheets, with their basal plane parallel to the flaky wear fragments. Such "mechanical" interpretation of the role of the contact pressure agrees with previous work of Muraki et al who studied the effect of roller hardness on the rolling sliding characteristics of MoDTC in the presence of ZDTP and concluded that the friction reduction effect increased with higher degree of roller hardness [10]. Yamamoto also reported that a necessary condition for improving the friction and wear characteristics of a lubricant was the formation of surface films composed of iron phosphates with high hardness and Mo-S compounds [11].…”

Section: Discussionsupporting

confidence: 90%

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Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

et al. 2004

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The layered structure and the rheological properties of anti-wear films generated in a rolling/sliding contact from lubricants containing zinc dialkyldithiophosphate (ZDTP) and/or molybdenum dialkyldithiocarbamate (MoDTC) additives have been studied by dynamic nanoindentation experiments coupled with a simple modelling of the stiffness measurements. Local nano-friction experiments were conducted with the same device in order to determine the evolution of the friction coefficient as a function of the applied pressure for the different lubricant formulations. For the MoDTC film, the applied pressure in the friction test remains low (<0.5 GPa) and the apparent friction coefficient is high (µ>0.4). For the tribofilms containing MoDTC together with ZDTP, which permits the applied pressure to increase up to a few GPa through some accommodation process, a very low friction domain appears (0.01<µ<0.05), located a few nanometers below the surface of the tribofilm. This low friction coefficient is attributed to the presence of MoS 2 planes sliding over each other in a favourable configuration obtained when the pressure is sufficiently high, which is made possible by the presence of ZDTP.

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Section: Discussionsupporting

confidence: 90%

“…A detailed review on published information on that topic was written by Willermet [9]. Non-chemical parameters such as characteristics of the solid antagonists (hardness, roughness) or test conditions (load, temperature, sliding speed) [3,10] also might influence the additive interactions.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

et al. 2004

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“…XPS and Raman have subsequently become widely used tools to study organo-molybdenum additive tribofilms [145][146] Figure 12. AFM lateral force map of surface rubbed in MoDTC solution showing low (dark) lateral force nanosheets [144] A recurrent theme in the literature is the existence of a "synergy" between MoDTC and ZDDP, where a combination of both types of additive in solution gives lower friction than MoDTC alone and/or lower wear than ZDDP alone [137] [147][148][149][150][151]. It is certainly the case that the rate of onset of friction reduction and in particular the longevity of friction reduction by MoDTC appears to be increased when ZDDP is present, although the actual occurrence of additive synergy, a quantitative concept based on the combined concentrations of pairs of additives [152] A significant practical problem associated with the use of organo-molybdenum FMs in engine lubricants is that their ability to reduce friction can be quite rapidly lost when they operate in oxidising environments at elevated temperature, such as in crankcase engines [157].…”

Section: Research On Oil-soluble Molybdenum Fmsmentioning

confidence: 99%

Friction Modifier Additives

2015

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The need for energy efficiency is leading to the growing use of additives that reduce friction in thin film boundary and mixed lubrication conditions. Several classes of such friction modifier additive exist, the main ones being organic friction modifiers, functionalised polymers, soluble organo-molybdenum additives and dispersed nanoparticles. All work in different ways. This paper reviews these four main types of lubricant friction modifier additive and outlines their history, research and the mechanisms by which they are currently believed to function. Aspects of their behaviour that are still not yet fully understood are highlighted.

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“…Formation of MoDTC tribofilms is affected by parameters such as temperature, MoDTC concentration, the presence of antioxidants and other lubricant additives as well as contact parameters such as the stroke length, sliding speed, slide-roll ratio and surface roughness of the sliding pair which in turn affect the friction performance of the additive [6][7][8][9][10][11][12]. Although there is a consensus within the research community that MoDTC reduces friction by formation of MoS 2 within the contact region, there is still no mechanistic model that links additive chemistry in a dynamic tribological system to friction and wear performance.…”

Section: Introductionmentioning

confidence: 99%

A methodology for Raman characterisation of MoDTC tribofilms and its application in investigating the influence of surface chemistry on friction performance of MoDTC lubricants

2015

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In this study, Raman spectroscopy has been employed to understand the influence of surface chemistry on friction in a tribocontact. Tribotests were conducted using molybdenum dialkyldithiocarbamate (MoDTC) lubricant in a steel/steel sliding contact. Firstly, surface chemistry in the high friction regime, at the beginning of the test, and in the low friction regime, after longer test duration is investigated. Secondly, the influence of temperature on the surface chemistry of the resulting wear scars is investigated. Results show that at the beginning of tribotests with MoDTC lubricant, iron oxides are formed in the tribocontact which result in high friction. At longer test durations, adsorbed MoDTC on the ferrous surface decomposes to form MoS 2 and low friction is observed. Surface chemistry at the tribocontact has been found to vary depending on the test temperature. At high temperatures, MoS 2 is formed which provides friction reduction while at low temperatures, molybdenum oxide and amorphous sulphur-rich molybdenum (MoS x ) compounds are formed which do not provide friction reduction. Furthermore, it has been shown that MoS 2 formed within the tribocontact at high temperatures has a slightly disordered crystal structure as a result of tribological processes.

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Synergistic effect on frictional characteristics under rolling-sliding conditions due to a combination of molybdenum dialkyldithiocarbamate and zinc dialkyldithiophosphate

Cited by 90 publications

References 14 publications

Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

Friction Modifier Additives

A methodology for Raman characterisation of MoDTC tribofilms and its application in investigating the influence of surface chemistry on friction performance of MoDTC lubricants

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