Friction and wear response of vegetable oils and their blends with mineral engine oil in a reciprocating sliding contact at severe contact conditions

Abstract

Although many studies investigating the tribological performance of pure vegetable oils have been conducted, a better understanding of vegetable oil tribological performance at extreme conditions is still needed. Similarly, little work has been carried out to study the influence of the vegetable oils on the performance of a lubricant formed from a blend of vegetable oil and conventional mineral engine oil. This work presents the tribological performance of vegetable oils, and their blends with mineral oil, in a high temperature and contact pressure reciprocating contact. Palm and soybean based vegetable oils were mixed with a commercial mineral engine oil at a 1:1 ratio by volume. The conventional mineral oil was also tested to provide a benchmark. The pure palm oil exhibited lower friction than soybean oil, but for wear performance, this was reversed. The friction performance of the palm oil was competitive to that of the mineral engine oil. The mineral engine oil was far superior in wear resistance over both vegetable oils. When blended with mineral engine oil both vegetable oils demonstrated a reduction in coefficient of friction when compared to their pure oil states. An improvement in wear performance was observed for both a blend of palm oil and mineral engine oil (25% improvement) and that of soybean and mineral engine oil (27% improvement). This work shows that for palm oil and soybean oil, the performance of a blended oil is influenced by its vegetable oil component and that tribological characteristics of vegetable oils are dominant. That said, the significant limitation of these vegetable oils is their ability to provide a satisfactory level of wear resistance. It is suggested that any future work in this area should have a greater emphasis on the enhancement of wear resistance.

Effects of Jatropha lubricant thermo-oxidation on the tribological behaviour of engine cylinder liners as measured by a reciprocating friction test

“…4c-d. Fresh JO and B20 had lower friction coefficients than EMO at both temperatures, which agrees with the behavior reported by other authors [6][7][8][9][10][11]. It suggests that JO enhanced the EMO´s lubricity properties in a fresh state.…”

“…Most bio-oils have been demonstrated to exhibit better lubricity properties than mineral oils when used in the boundary lubrication regime. This is attributable to the high proportion of free fatty acids they contain, which act as effective friction modifiers [6][7][8][9][10][11]. However, the confident total use of bio-oils as engine lubricants has not been authenticated since they exhibit poor oxidation stability and generate considerable high wear compared with mineral oils, which may damage engine components with their long-term use [9,10,[12][13][14][15].…”

Tribological evaluation of the Jatropha and Tung-based oils as bio-lubricants on Al-7050-T7451 alloy

“…The lower amount of unsaturations in Jatropha oil provided lower average COF, as also found in other oils in the literature [13,14,21,30]. The lower concentration of unsaturations provides a better lubricant film with lower resistance to movement between tribological pairs, favoring low COF [46]. However, these gaps between the molecules of oils favor the metal/ metal contact, leading to abrasion wear.…”

Vegetable Oil Based Lubricants: Challenges and Prospects

“…Bahari et al [31] studied the friction and wear of palm and soybean blends with commercial mineral engine oil SAE 15W40 for high temperature and severe contact conditions application using a linear reciprocating rig. Four samples were prepared: palm oil (PO), soybean oil (SBO), 50% mineral oil+50% palm oil and 50% mineral oil +50% soybean oil and tested for friction, wear, viscosity, and oxidation stability.…”