Lube-Tech
Tribological study of the performance of base oils and greases was conducted by using an SRV rig. The tests were run within the boundary lubrication region under the following conditions: an applied load of 150 N (corresponding to 2.5GPa maximum Hertzian pressure) at 40 °C, with a sliding frequency of 50 Hz and an amplitude of 1 mm. The wear of the tested balls and discs was measured with a 3D profilometer (New View 7300 3D, Middlefield, CT, USA).
Picture 1: Shows the oil sample between the Disc and Ball in SRV-rig.
Figure 4 illustrates the measured friction coefficient (COF) for BO1 and lithium and lithium complex greases. After just a few minutes of running time, the measured COF of BO1 increased by almost 20 percent, from 0.111 up to about 0.142. After an additional 20 min., the COF started to dive and reached a lower stable level of about 0.13. Grease A (lithium grease), however, showed smooth and stable COF within the entire running cycle, while the COF of Grease C (lithium complex grease) increased at the end of the running period to about 0.160.
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.125 page 5
Figure 5 illustrates the measured COF of BO2 and the greases based upon BO2 (Grease B and Grease D). The COF was low and stable for all three products. This emphasized the film strength of BO2 as a lubricant.
Figure 5: Measured friction coefficient as a function of time for BO2, Grease B and Grease D.
The measured smaller wear scars on the balls and discs are consistent with the lower and more stable friction coefficients for BO2 and the greases based on BO2, especially for lithium complex grease, versus BO1 and the greases based on BO1, Table 4.
Table 4: Measured wear scars on balls and discs for the base oils and greases.
Appendix A contains the pictures of the wear scars on the discs and balls for each sample after the test run.
Summary
Figure 4: Measured friction coefficient as a function of time for BO1, Grease A and Grease C.
This multidisciplinary study showed that high viscosity naphthenic oils can be used successfully in the production of lubricating greases with various thickener systems. The characterization of the greases revealed that good to excellent properties were obtained despite low thickener content.
36 LUBE MAGAZINE NO.154 DECEMBER 2019
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