Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE Figure 22. GMO addition reduces wear caused by MoDTC on both ball and disc
In comparing PFM with GMO and MoDTC only containing formulations, it was observed that the PFM provided the highest level of wear protection for both the ball and the disc (figure 23). The PFM gave a modest reduction in friction (0.13; 5% reduction) compared to reference oil when used at 0.5% treat-rate.
No.110 page 7
Table 3. Traffic light table indicating relative performance of FMs and combinations of FMs
The following observations are based on the effect of friction modifiers when top-treated into a 5W30 ACEA C3 engine oil:
3.1. MoDTC
a. MoDTC had a strong positive effect in reducing friction in a steel – steel contact (the lowest friction of any additive or combination of additives) but it came at the expense of increased wear.
b. MoDTC did not reduce friction in a sp2 ;Cr doped; 0%
hydrogen DLC ball – steel disc contact and resulted in very high wear of the DLC coating.
Figure 23. PFM1 reduces wear on ball and disc compared to baseline formulation
Like the GMO + MoDTC combination, the combination of PFM and MoDTC resulted in lower friction (0.11) but not as low as for MoDTC alone (0.08). PFM and MoDTC combined were observed to result in wear on both the steel ball and on the steel disc comparable to those observed for MoDTC alone and GMO + MoDTC formulations. Under these test conditions it appears that wear results directly from the presence of MoDTC.
3. Comparison of FMs by Contact Type Table 3 summarises the effectiveness of the different FMs and combination of FMs for all three types of DLC in contact with either the cast iron pin or steel counter-face, and a steel – steel contact. Green boxes indicate a strong positive effect in reducing friction or wear, yellow indicates some positive effect in reducing friction or wear and red indicates no evidence of a positive effect on friction and wear, and indeed may result in higher friction and wear.
c. MoDTC did reduce friction in a sp2 ; 15% hydrogen DLC plate
– cast iron contact but resulted in very high wear of the DLC coating and a transfer of the coating from disc to cast iron pin.
d. MoDTC did reduce friction in a 50% sp3 ; 40% hydrogen DLC
ball – steel disc contact but resulted in very high wear of the DLC coating.
3.2. Glycerol Mono-Oleate a. GMO has a negative effect on friction and wear in a steel – steel contact.
b. GMO did reduce friction in a sp2 ;Cr doped; 0% hydrogen DLC
ball – steel disc contact and resulted in lower wear of the DLC coating. Of all the FMs and combinations of FMs, GMO was the most effective friction modifier on sp2
;Cr doped; 0% hydrogen
DLC in minimising DLC wear. c. GMO did reduce friction in a 50% sp3
; 40% hydrogen DLC
ball – steel disc contact and provided some reduction in wear of the DLC coating.
LUBE MAGAZINE NO.139 JUNE 2017
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