A new approach on grease tribology in sealing technology: Influence of the thickener particles

Sommer, Max; Haas, Werner

doi:10.1016/j.triboint.2016.08.002

Cited by 19 publications

(11 citation statements)

References 21 publications

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“…But the most common problem is linked to the vacuum environment of the mentioned equipment, where the grease sample is required to be submitted either to a cryogenic treatment or to oil removal. In many studies, the oil that obstructs the view of the underlying structure of soap is eliminated. − Since grease contains 80–95% oil, it is often argued that the thickener structure may be distorted if oil is washed out and that such a micrograph is ambiguous . On the contrary, the AFM technique allows us to define the arrangement of thickener structure in the presence of the base oil, thus considering the thickener–oil medium interactions, although generally with lower image resolution than SEM. , …”

Section: Resultsmentioning

confidence: 99%

“…Thickening agent plays an important role in both the rheological and tribological properties of the grease; thus a large number of thickeners such as fatty acid soap of lithium, sodium, calcium, barium, and aluminum are most commonly used and being developed. − That is why it is not always sensible to ascribe the frictional and antiwear behavior to a single component of grease, but it is usually determined by the interactive forces between grease elements, e.g., base oil, thickener, and additives, which in turn are strongly governed by the specific operating conditions, e.g., load and speed . Micro- and nanoscale structures of these thickeners are revealed by scanning (SEM) and transmission (TEM) electron microscopy methods in the form of fibers, spheres, and platelets, with each of them endowing different consistency and aimed at different mechanical applications. − …”

Section: Introductionmentioning

confidence: 99%

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Graphene-Reinforced Lithium Grease for Antifriction and Antiwear

Lin

Rustamov

Zhang

et al. 2020

ACS Appl. Nano Mater.

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Graphene has attracted tremendous attention as a promising additive in lubricants due to its unique lamellar structure and excellent mechanical strength. Yet, unlike its use in oil and water lubricants, the amount of graphene additive should be considered when it is introduced into the grease which is a two-phase colloid. In this work, graphene was added into the lithium grease in different concentrations, and lubrication behaviors were investigated using a four-ball testing method under various operating conditions. Prior to the four-ball friction tests, graphene and grease materials were characterized by scanning (SEM) and transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and Raman spectroscopy. Friction test results demonstrate that the graphene concentration in grease varies at different tribological contact conditions to reach the optimum lubrication behavior. On the basis of the results from friction tests and worn scar morphology analysis, a lubrication mechanism was proposed to better understand the interactions among grease elements, e.g. graphene, thickener, and base oil, during the shearing process. It is believed that thickener soap actively participates in the lubrication process at low speeds by releasing enough oil into the friction contacts under high load. Meanwhile, less graphene concentration is required to strengthen the base grease by inhibiting and avoiding severe wear. High rotational speeds negatively affect the “oil-bleed” capability of thickener under lower contact loads due to the churning loss at high centrifugal force. Thus, extra graphene additives are required to retain more oil and separate the contact surfaces. This, in turn, promotes the formation of protective tribofilm on the interface which is the key to the enhancement of antifriction and antiwear performance.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Graphene-Reinforced Lithium Grease for Antifriction and Antiwear

Lin

Rustamov

Zhang

et al. 2020

ACS Appl. Nano Mater.

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“…Lubricating grease is a colloid disperse system in which base stock (mineral or synthetic oil) is trapped in three dimensional network of thickener [1] . Grease has obvious advantages over lubricating oil in terms of load-bearing capacity, sealing and corrosion prevention, because grease does not flow away from the contact surface [2,3] .…”

Section: Introductionmentioning

confidence: 99%

The Enhancement of Overall Performance of Lubricating Grease by Adding Layered Double Hydroxides

Li¹,

Zhou²,

Xue³

et al. 2023

Preprint

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In this paper, MgAl Layered double hydroxides (LDH) were synthesized by co-precipitation method using a colloid mill and characterized by XRD, IR and SEM. The LDHs was repeatedly tested and compared with different bearing lifetime tester in lithium base grease, and it was found that the environmental-friendly LDHs had greater performance than the traditional antioxidant, and it was the development direction of a new generation of environmental-friendly antioxidants in the future. By adding LDHs into large electric shovel greats (GRK-A) in open-pit coal mine, it can be seen by PDSC evaluation that the service lifetime of grease is extended by 20% while the overall performance of grease is not affected. With the increase of LDHs addition, the grease sample gets the greater activation energy, the stronger thermal oxidation and decomposition resistance. Comparing the energy storage modulus and flow transition index at different temperatures, it can be seen that adding the right amount of LDHs needs close attention for the system oxidation resistance and viscoelasticity. For the electric shovel grease system, the best oxidation resistance and rheological properties can be achieved by adding 2% of LDHs. The rheological viscosity-temperature curves show that the grease samples with different ratios of solid LDHs have better low-temperature properties than the mine grease.

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“…LCG is a multiphase system, consisting of three main components: base oil, thickener, and additive. 9,10 Among them, base oil as dispersion medium, accounting for 65% to 95% of total mass of grease, its quality, and property largely determine the performance of lubricating grease. 11 The contribution to thickener for physical properties and lubrication function of grease is often neglected.…”

Section: Introductionmentioning

confidence: 99%

Regulating performance characteristics of lithium complex greases via dibasic acids

Ren

et al. 2020

Lubrication Science

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Thickener as an important ingredient affects the performance characteristics of lubricating grease. Here, seven lithium complex greases (LCGs) were prepared by saponification of 12‐OH stearic acid and low molecular weight dibasic acids (including adipic acid, sebacic acid, phthalic acid, dodecanedioic acid, and the combination of sebacic acid and phthalic acid in different molar ratios) with LiOH, using polyalphaolefin (PAO 40) as base oil. Physical properties and lubrication function of as‐prepared LCGs were evaluated in detail, and the friction mechanism was explored via analysis on the morphologies and composition of worn surfaces. Results illustrate that the saponification of mixed 12‐OH stearic acid and sebacic acid with LiOH provides good thickener for improving the physico‐chemical performance of LCG, while the thickener prepared by 12‐OH stearic acid and adipic acid with LiOH enhances lubrication function of LCG, mainly depending on synergy of grease film and tribo‐chemical reaction film.

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A new approach on grease tribology in sealing technology: Influence of the thickener particles

Cited by 19 publications

References 21 publications

Graphene-Reinforced Lithium Grease for Antifriction and Antiwear

Graphene-Reinforced Lithium Grease for Antifriction and Antiwear

The Enhancement of Overall Performance of Lubricating Grease by Adding Layered Double Hydroxides

Regulating performance characteristics of lithium complex greases via dibasic acids

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