Additives

Braun, Jürgen

doi:10.1002/9783527645565.ch6

Cited by 6 publications

(4 citation statements)

References 12 publications

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“…A mineral base oil was, therefore, used in this study. It is state of the art to include antiwear (AW) and extreme pressure (EP) additives to the grease to prevent premature failures of bearings due to wear (Hsu, 2004; Braun, 2017; Kato, 2002; Czichos and Habig, 2015). AW/EP additives consist of a wide range of chemical compounds.…”

Section: Introductionmentioning

confidence: 99%

“…The functional groups of all AW/EP additives contain a dipole (Hsu, 2004; Naveira-Suarez et al , 2011). As a result, the polar additives adsorb on the bearings’ surfaces (Braun, 2017; Hsu, 2004; Naveira-Suarez et al , 2011). Under suitable tribological loads, the additives are probably activated by shear stresses and thermal loads (Brizmer et al , 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Under suitable tribological loads, the additives are probably activated by shear stresses and thermal loads (Brizmer et al , 2017). They form chemical bonds with the bearing’s surface, thereby creating tribofilms (Spikes, 2004; Gosvami et al , 2015; Hsu, 2004; Braun, 2017). Such additive-based tribofilms prevent a direct contact of bearing material and micro welding of the metallic asperities (Czichos, 1978; Hsu, 2004; Braun, 2017; Czichos and Habig, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Influence of temperature on wear performance of greases in rolling bearings

Rosenkranz

Richter

Jacobs

et al. 2021

ILT

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Purpose Rolling bearing operation under mixed and boundary lubrication conditions may lead to heavy adhesive or abrasive wear, which may lead to wear-induced rolling bearing failure. The purpose of this paper is to investigate the wear protection capabilities of different grease compositions at varying temperatures. It is considered that the temperature influences the lubrication conditions, the behaviour of grease components, namely, bleed oil and thickener, as well as the tribofilm formation due to tribo-chemical interactions between additives and surfaces. Design/methodology/approach In this study, four different greases were produced on the basis of a mineral base oil by varying the thickener and the addition of ZDDP. Various grease-lubricated rolling bearing experiments were conducted in a wide temperature range from 0°C to 120°C. Subsequently, the wear pattern, tribofilm formation and grease structures were analysed. Thereby, the influence of the different grease thickeners and the performance of ZDDP as a common antiwear and extreme pressure additive was evaluated. Findings The results show a strong temperature-dependency and allow a classification of temperature ranges concerning wear protection. At low temperatures, all greases provide a very good wear protection without the evidence of additive-based tribofilm formation. In the experiments at elevated temperatures, ZDDP tribofilms were formed. The formation depends on the thickener type: in comparison to lithium thickener, polyurea thickener favours more protective tribofilms at the same temperature. The experimental results show that medium temperatures in the range of 40°C–60°C are critical concerning wear due to the insufficient tribolayer formation and limited load carrying capacity of the grease. Originality/value Temperature is a key operating parameter for grease lubrication in roller bearings. The experimental work enables consideration of different impact pathways of temperature by combining roller bearing tests and microanalysis.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of temperature on wear performance of greases in rolling bearings

Rosenkranz

Richter

Jacobs

et al. 2021

ILT

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“…The formulations are completely proprietary and the information about the additives is scantily available on demand. For example, engine oil will contain anti-wear additive (AWA) and anti-friction additive (AFA) apart from several other additives such as viscosity index improvers (VIIs), anti-oxidants (AOs), detergents etc and gear oil will definitely contain extreme-pressure additive (EPA) along with so many other additives [1,2]. FFOs, thus are tailored as per usability by mixing multiple additives such as Friction modifiers (FM) MODTC, ZDDP (zinc dialkyldithiophosphates), detergents, dispersants and other Sulphur/Phosphorus based EP additives [3,4] and information about their types, amounts or combinations is always classified.…”

Section: Introductionmentioning

confidence: 99%

Exploration of PTFE sub-micron particles for enhancing the performance of commercial oils

Solanki¹,

Saini²,

Bijwe³

2021

Surf. Topogr.: Metrol. Prop.

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This paper reports on the tribo-performance enhancement of commercial gear oil and engine oil by inclusion of PTFE particles of submicron (230 nm) size (SMPs). It also reports on the investigations on various concentrations of SMPs to find the optimum doses. Results revealed that optimum dosage of 6 and 3 wt.% SMPs led to a significant improvement in EP property by 175% and 58% respectively in Engine oil and Gear oil. The EP performance of PTFE added engine oil surpassed that of PTFE added-gear oil confirming that it can be used as multipurpose oil. Importantly anti-wear and anti-friction properties also showed improvement confirming no antagonistic influence of PTFE particles on selected commercial oils. Synergistic action between SMPs and other additives led to formation of stable tribo-film as a result of chemical interaction of mating surfaces. The mechanisms involved were analyzed by investigating worn surfaces using SEM-EDX, x ray photoelectron spectroscopy (XPS) techniques. The stability of suspension in case of engine oils was up to 2 months and for gear oil it did not show any deterioration in the observed period of 4 months.

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