Effects of basestock and additive chemistry on traction testing

Abstract

Over the past few years there have been numerous papers and articles published using the Mini-Traction Machine (MTM) test rig for transport lubricant applications. This rig has gained popularity by allowing the measurement of both high and low entrainment speeds in a single instrument. In this study, the MTM clearly demonstrates the effects of friction modifier on high and low polarity basestocks. It can be observed in the slide-roll ratio curves the friction modifier glycerol monooleate (GMO) is most effective in naphthenic mineral oil and least effective in polyol ester. Additionally, we have used the MTM rig to differentiate the traction of various organic friction modifiers, as well as, investigated the behavior of a variety of overbased sulfonate detergents. Depending on the nature of the friction modifier the traction can be increased or decreased under various conditions of temperature and slide-roll ratio. Conversely, the addition of overbased sulfonate detergents increases the traction at high speeds and decreases the traction at low speeds, resulting in an overall flattening of the traction curve.

Study of surface films of overbased sulfonates and sulfurized olefins by X-Ray Absorption Near Edge Structure (XANES) spectroscopy

“…The increased formation of this FeS/ CaSO 4 film is reflected in improved tribotester performance (four-ball EP and Reichert). This observation is consistent with previous XPS and Auger results, which display an increased Ca and S concentration on the metal surfaces [23]. Thus we can propose the following mechanism for the tribofilm formation:…”

“…This suggests that sulfurized olefin is oxidized to sulfate on the surface, which was also observed by the K-edge. There is no significant evidence of the sulfonate on the surface, which is in agreement with previous XPS and Auger spectroscopy [23]. It is not surprising that spectra (4)-(6) display small sulfate peaks since there is a reduced amount of overbased calcium sulfonate and sulfurized olefin in the oils, but spectra (7) and (8) which contain a considerable amount of overbased magnesium sulfonate are also quite weak.…”

Molecular Dynamics Simulations of Glycerol Monooleate Confined between Mica Surfaces

“…The molecular structure of GMO is shown in Figure . The effects of GMO on friction have been studied extensively in systems including diamondlike carbon, − lubricant base stocks, and mixtures with phosphates . GMO is known to self-assemble into normal and reverse micelles (RMs) in aqueous and nonaqueous media, respectively.…”

Study of surface films of crystalline and amorphous overbased sulfonates and sulfurized olefins by X-ray absorption near edge structure (XANES) spectroscopy

“…From XPS analysis it appears that C300C and C400A both form thin layers of CaCO 3 on top of a thicker layer of iron sulfide on the surface of the test piece [12]. Additional AES analysis revealed the presence of both S (from FeS) and Ca (from CaCO 3 ) covering the surface, where the Ca is more prevalent and evenly coated and the S is clustered and lower in concentration.…”

“…In our XPS and AES studies we have focused on the difference between the surface tribofilms created from samples containing crystalline overbased calcium sulfonate (C300C) and amorphous overbased calcium sulfonate (C400A) [12,13]. From XPS analysis it appears that C300C and C400A both form thin layers of CaCO 3 on top of a thicker layer of iron sulfide on the surface of the test piece [12].…”