Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE Figure 17. PFM1, increase of wear volume on sp2 DLC ball
The combination of MoDTC and PFM gave a surprisingly good performance compared to either additive used alone. Whilst not achieving the level of wear protection provided by GMO only, this combination resulted in the lowest friction profile (<0.10; >20% reduction compared to the ACEA C3 reference oil). With respect to wear, the combination of PFM and MoDTC provided a 40% reduction in wear on the sp2
;Cr doped; 0% hydrogen DLC
ball (48,000 µm3) but a 20% increase in wear on the steel disc counter-face (59,000 µm3
). Figure 20. Comparison of wear for 5W30 baseline oil in different configurations
No.110 page 6
When comparing the wear performance of the 5W30 baseline oil, the steel – steel contact demonstrated ball wear of a similar magnitude to the sp2
;Cr doped; 0% hydrogen DLC ball, which
was 30 times greater than the ball wear observed with the 50% sp3
; 40% hydrogen ball (figure 20). The disc wear was lower than was observed in the sp2
– steel disc configuration but 2.5 times greater than the level of the steel disc wear observed with the 50% sp3 DLC ball – steel disc contact.
;Cr doped; 0% hydrogen DLC ball ; 40% hydrogen
Figure 18. Addition of PFM1 to MoDTC, surprising reduction in sp2
DLC ball wear
2.4 Steel Disc – Steel Ball To complete the study, the results for steel-steel friction and wear were repeated for all the FM and FM combinations.
In comparison to the two DLCs investigated as part of the Croda in-house work, steel ball – steel disc contact is the highest friction contact, with the 5W30 ACEA C3 reference oil having a coefficient of friction of 0.14 in the boundary regime (figure 19).
Figure 21. Wear profiles for steel ball – steel disc
The reference oil top-treated with GMO showed no reduction in friction and GMO may be responsible for an increase in wear (140,000 µm3
these test conditions (116,000 µm3
) compared to the 5W30 reference fluid under ).
MoDTC provides a substantial reduction in friction (0.08; 40% decrease), compared to the reference oil. However, a 30% increase in ball wear (150,000 µm3 was lower (20,000 µm3 (36,000 µm3
) was observed. Disc wear ) than the 5W30 ACEA C3 reference fluid ).
Figure 19. Stribeck Curves for Steel Ball – Steel Disc
38 LUBE MAGAZINE NO.139 JUNE 2017
GMO + MoDTC when used in combination also provided a very strong reduction in friction (0.09; 35% decrease) compared to the reference oil but not as low as MoDTC by itself. This combination of inorganic and organic friction modifier resulted in the lowest wear measured on both steel ball and steel disc.
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