Investigation of the tribochemical interactions of a tungsten-doped diamond-like carbon coating (W-DLC) with formulated palm trimethylolpropane ester (TMP) and polyalphaolefin (PAO)

Zahid, Rehan; Hassan, Masjuki Bin Haji; Alabdulkarem, Abdullah; Varman, M.; Mufti, Riaz Ahmad; Kalam, M.A.; Zulkifli, Norhayah; Gulzar, Mubashir; Lee, Tom

doi:10.1039/c6ra27743h

Cited by 19 publications

(14 citation statements)

References 75 publications

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“…To improve the thermo-oxidative stability and low temperature characteristics of palm oil, it was chemically modified by transesterification process. The detailed procedure and mechanism for producing palm trimethylolpropane ester (TMP) are described in our previous research (Zahid et al, 2017). As valve train assembly mostly operates in boundary lubrication regime, anti-wear additives and friction modifiers (GMO, MoDTC and ZDDP) were used to further enhance the tribological performance of above-mentioned base oils.…”

Section: Formulation Of Lubricantsmentioning

confidence: 99%

Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system

Zahid

Hassan

Alabdulkarem

et al. 2018

ILT

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Purpose There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives. Design/methodology/approach In this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior. Findings In additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize specialized friction modifiers, anti-wear and extreme pressure additives for TMP before using it as engine lubricant base-oil. Originality/value In this study, additive-free and formulated versions of bio-lubricant are tested for cam/tappet interface of direct acting valve train system of commercial passenger car diesel engine for the very test time. Another important aspect of this research was comparison of important tribological performance parameters (friction torque, wear, rotational speed of tappet) of TMP-based lubricants with conventional lubricant base oil, that is, PAO and its formulated version.

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Section: Formulation Of Lubricantsmentioning

confidence: 99%

Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system

Zahid

Hassan

Alabdulkarem

et al. 2018

ILT

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“…A possible justification for high wear coefficient values in the presence of TMP can be formation of organic acids due to the thermal decomposition of esters, which chemically attacked the interacting surfaces and formed soft oxide layer. 29 This oxide layer possessed low shear strength due to which it facilitated the sliding between the Figure 5. Wear coefficients of plates of ta-C/ta-C, ta-C/steel, and steel/steel contacts with (a) polyalphaolefin and (b) trimethylolpropane ester-based lubricants.…”

Section: Tribological Resultsmentioning

confidence: 99%

“…A possible justification for high wear coefficient values in the presence of TMP can be formation of organic acids due to the thermal decomposition of esters, which chemically attacked the interacting surfaces and formed soft oxide layer. 29 This oxide layer possessed low shear strength due to which it facilitated the sliding between the interacting surfaces and resulted in low friction coefficients. However, it can be easily removed from the contact, due to its weak adhesion, by the scraping action of the counterbody and reformed by further chemical reaction resulting in accelerated wearing.…”

Section: Resultsmentioning

confidence: 99%

Tribological compatibility analysis of conventional lubricant additives with palm trimethylolpropane ester (TMP) and tetrahedral amorphous diamond-like carbon coating (ta-C)

Zahid

Mufti

Gulzar

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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Modern industrial applications involve rigorous operating conditions due to which lubricant either slips out of the contact or its thin layer resides between the interacting surfaces. Deposition of diamond-like carbon coatings and using lubricants capable of physically adsorbing on the interacting surfaces can significantly improve tribological performance. In this study, tribological compatibility of glycerol mono-oleate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate with palm trimethylolpropane ester and tetrahedral amorphous diamond-like carbon coating has been investigated using universal wear testing machine. For comparison, additive-free and formulated versions of polyalphaolefin were used. Moreover, spectroscopic techniques were used to investigate mechanisms responsible for a particular tribological behavior. Among base oils, trimethylolpropane ester proved to be more effective in enhancing friction performance and mitigating wear of contacts when one of the interacting surfaces was ferrous-based. Self-mated tetrahedral amorphous diamond-like carbon coating surfaces resulted in lowest values of friction and wear coefficient of balls.

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“…It is believed that graphitization occurred on the worn surfaces of the W-DLC film at high temperatures, and the graphite phase was easily sheared, which made MoS 2 difficult to adhere to the wear tracks of the W-DLC films; thus, the MoS 2 peaks on the steel balls were prominent. In addition, for the steel balls, FeO and Fe 2 O 3 peaks appeared on the worn surfaces of the W-DLC films annealed at 150-400 °C [49], located at 775 cm −1 . Furthermore, a peak was observed at 612 cm −1 , which was assumed to be Fe 3 O 4 [50].…”

Section: Pao + Modtc Lubricationmentioning

confidence: 93%

Effects of annealing treatment on tribological behavior of tungsten-doped diamond-like carbon film under lubrication (Part 2): Tribological behavior under MoDTC lubrication

et al. 2021

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Molybdenum dialkyldithiocarbamate (MoDTC) is widely used as a friction modifier in engine lubricating oil. Under MoDTC lubrication, the friction and wear behaviors of tungsten-doped diamond-like carbon (W-DLC) films annealed at 100–400 °C were discussed and evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. Under (polymerized alpha olefin) PAO + MoDTC lubrication, the coefficient of friction of all samples decreased, but the wear rates of the W-DLC films annealed at 300 °C increased significantly. By interacting with zinc dialkyldithiophosphate (ZDDP), the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces.

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Investigation of the tribochemical interactions of a tungsten-doped diamond-like carbon coating (W-DLC) with formulated palm trimethylolpropane ester (TMP) and polyalphaolefin (PAO)

Abstract: Modern day industrial applications involve rigorous operating conditions, which include high temperature, heavy applied loads, and starved lubrication conditions.

Cited by 19 publications

References 75 publications

Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system

Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system

Tribological compatibility analysis of conventional lubricant additives with palm trimethylolpropane ester (TMP) and tetrahedral amorphous diamond-like carbon coating (ta-C)

Effects of annealing treatment on tribological behavior of tungsten-doped diamond-like carbon film under lubrication (Part 2): Tribological behavior under MoDTC lubrication

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