Lube-Tech
SRV friction and wear SRV was used to further explore the temperature component in tribofilm formation. Figure 6 shows the results for the custom temperature ramp friction profile for both fresh and aged oils. The benefit of Mo-DTC in fresh oil (Formula A) is well demonstrated in this test. Beginning at 80 °C, there is a significant drop in friction when using Mo-DTC in fresh oil. Likewise, the diminished returns of Mo-DTC in aged oil is also seen, such that a 100 °C activation temperature is needed in aged oil. Above this temperature, lower friction is achieved, but it never achieves the same low value as seen in fresh oil. This loss in aged-friction can be mitigated somewhat through a combination of Mo-DTC and Mo-AMIDE (Formula D). With this combination, a consistent friction performance can be achieved across both fresh and aged oils.
The SRV data also demonstrates that aged oil performance can be significantly different than that of fresh oil, independent of formulation. As a single component B-AMIDE (Formula C) becomes a friction modifier in this EV formulation, with activation around 80 °C. It outperforms the traditional Mo-DTC friction modifier (Formula A) until 120 °C, and then matches performance from thereon. Likewise binary additive combinations of B-AMIDE with either of the molybdenum friction modifiers gives a similar performance (Formulas E and F).
Two of the three ternary additive combinations outperform all other additive combinations in the aged oil. Both Formulas G and H contain a minor fraction of B-AMIDE. The major fraction is split 2:1 between the two molybdenum friction modifiers, with Mo-DTC being the majority in FORMULA G, and Mo-AMIDE being the majority in Formula H. Both formulas G and H consistently give lower friction across the entire temperature range, and the lowest activation temperature of all formulations, at approximately 60 °C.
32 LUBE MAGAZINE NO.180 APRIL 2024
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.151 page 6
Figure 6: SRV friction profile relative to baseline formula 00.
Wear volume results for each of the formulations run in the SRV are shown in Figure 7. For the fresh oil, all formulations are statistically similar to the baseline, indicating no additional wear benefit in this
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