Ageing impact on tribological properties of MoDTC-containing base oil

Feo, M. De; Minfray, Clotilde; Bouchet, Maria Isabel De Barros; Thiébaut, Benoît; Mogne, Th. Le; Vacher, Béatrice; Martin, Jean‐Michel

doi:10.1016/j.triboint.2015.04.014

Cited by 55 publications

(45 citation statements)

References 12 publications

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“…To simulate the ageing process, a thermoscontrolled heater and round-bottom flask containing 300 mL of oil were used. The flask is connected to a condenser to reduce the evaporation losses of the more volatiles components [13].…”

Section: Degradation Proceduresmentioning

confidence: 99%

MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation

Feo

Bouchet

Minfray

et al. 2016

Wear

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Recently Diamond-Like Carbon (DLC) coatings have attracted considerable attention due to their low friction, high hardness, good wear and corrosion resistance, high thermal and chemical stability. Although considerable research has been conducted on the effect of molybdenum-based additive, e.g. molybdenum dithiocarbamate (MoDTC), on the boundary lubrication of DLC coatings, the wear mechanisms leading to the coating removal are not fully understood to date. Moreover, the impact of degradation of MoDTC-containing base oil on the tribological properties of DLC coatings has not been investigated. This study could help to elucidate the mechanisms by which the coating is worn out in presence of MoDTC-containing base oil. In this work, the friction and wear performances of different types of DLC coatings with different hydrogen contents and doping elements have been investigated in presence of MoDTC-containing base oil. To enable the correlation between these changes and the modification of contact surface chemistry, tribofilms generated during friction were investigated by SEM combined with Energy Dispersive X-ray Spectrometry (EDX) and X-ray Photoelectron Spectroscopy (XPS). A new mechanism explaining the severe wear experienced by DLC coatings when lubricated with a MoDTC-containing base oil is proposed.

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Section: Degradation Proceduresmentioning

confidence: 99%

MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation

Feo

Bouchet

Minfray

et al. 2016

Wear

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“…From the FIB-TEM results, formation of long and crystalline MoS 2 akes on the surface of TiO 2 APS coatings was observed compared to the short akes embedded in an amorphous matrix on the surface of steel. 10 It was also shown that wear resistant Magneli phases are formed in case of TiO 2 APS, decreasing wear even when the contact was lubricated with only base oil. This type of wear reduction had been previously observed in Ti-based materials 19,21 and attributed to the formation of Magneli phases.…”

Section: Introductionmentioning

confidence: 98%

“…Majority of the experimental and theoretical studies involving decomposition of MoDTC have been carried out in case of steel/ steel contacts. 7,10,[15][16][17] However, it was suggested from our previous work 1 that additives could behave in different ways on a material with different chemical compositions. It was shown that better friction behavior is obtained in case of steel/TiO 2 APS coating (m z 0.040) than with steel/reference steel (m z 0.055).…”

Section: Introductionmentioning

confidence: 99%

Tribocatalytic behaviour of a TiO₂ atmospheric plasma spray (APS) coating in the presence of the friction modifier MoDTC: a parametric study

et al. 2018

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“…However, it is not clear how significant is the role of NO x in this process and thus whether MoDTC loss is likely to be specifically a problem in engine oils. Although many studies have used air/NO x mixture and shown in ageing tests that this depletes MoDTC and results in it losing the ability to reduce friction, similar effects have been seen when only air is present during oxidation [7,18]. This study aims to explore the effect of NO x on the ability of MoDTC to reduce friction.…”

Section: Introductionmentioning

confidence: 97%

“…It was shown using XPS and HRTEM that as the concentration of MoDTC decreases in the lubricant due to oxidative ageing, the MoS 2 sheets are modified, becoming smaller and fewer in number and possibly partially oxidised [17,18].…”

Section: Introductionmentioning

confidence: 99%

Influence of NO x and Air on the Ageing Behaviour of MoDTC

et al. 2017

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Molybdenum dialkyldithiocarbamates (MoDTCs) are very effective friction modifier additives for use in engine oils and other lubricants. However, as engine oils age during extended drain intervals, MoDTCs can lose some or all of their ability to reduce friction and this is generally believed to result from their oxidative degradation. In this study, MoDTC solutions in base oil have been subjected to oil ageing in a controlled NO x /air flow rate, controlled temperature test apparatus and the effect of ageing on the ability of the MoDTC to reduce friction has been explored. As shown in previous studies, the additive's friction-reducing properties are completely lost after a quite short period of ageing at 160°C. However, it was found that at this temperature the presence of NO x has little if any influence on the rate of friction loss, indicating that the latter is controlled primarily by the rate of reaction of oxygen with the base oil and thus the rate of consumption of MoDTC as a peroxide decomposer. By contrast, when ageing tests are carried out at lower temperatures it is found that NO x has a very strong effect on the rate at which MoDTC loses its ability to reduce friction, so that at 100°C NO x accelerates this rate by two orders of magnitude compared to air alone. This suggests that at low temperatures the rate at which MoDTC is consumed is controlled by its reaction as a radical inhibitor with NO x species.

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Ageing impact on tribological properties of MoDTC-containing base oil

Cited by 55 publications

References 12 publications

MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation

MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation

Tribocatalytic behaviour of a TiO₂ atmospheric plasma spray (APS) coating in the presence of the friction modifier MoDTC: a parametric study

Influence of NO x and Air on the Ageing Behaviour of MoDTC

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Ageing impact on tribological properties of MoDTC-containing base oil

Cited by 55 publications

References 12 publications

MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation

MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation

Tribocatalytic behaviour of a TiO2 atmospheric plasma spray (APS) coating in the presence of the friction modifier MoDTC: a parametric study

Influence of NO x and Air on the Ageing Behaviour of MoDTC

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Product

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Tribocatalytic behaviour of a TiO₂ atmospheric plasma spray (APS) coating in the presence of the friction modifier MoDTC: a parametric study