Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
3.3. Polymeric Friction Modifier a. PFMs have a positive effect in reducing friction in a steel – steel contact and they provided the highest wear protection of any single FM or combination of friction modifiers.
b. PFMs did not reduce friction in a sp2 ;Cr doped; 0% hydrogen
DLC ball – steel disc contact and resulted in high wear of the DLC coating.
c. PFMs did reduce friction in a sp2 ; 15% hydrogen DLC ball –
cast iron pin contact and provided the highest wear protection of all friction modifiers or combinations of friction modifiers.
d. PFMs did reduce friction in a 50% sp3 ; 40% hydrogen DLC ball
– steel disc contact and provided the highest wear protection of all friction modifiers or combinations of friction modifiers.
3.4. MoDTC / GMO Combined a. MoDTC / GMO combination had a strong positive effect on friction and wear in a steel – steel contact. Of all the additives and combinations tested, this combination gave the lowest wear in the steel – steel contact.
b. MoDTC / GMO combination did not reduce friction in a sp2 ;Cr
doped; 0% hydrogen DLC ball – cast iron pin contact but did result in lower wear of the DLC coating. The combination of MoDTC and GMO gave inferior performance compared to GMO alone in a sp2 configuration.
;Cr doped; 0% hydrogen DLC ball – steel disc c. MoDTC / GMO did reduce friction in a 50% sp3 ; 40%
hydrogen DLC ball – steel disc contact but did not provide any significant additional wear protection compared to the reference oil or to GMO alone.
3.5. MoDTC / PFM Combination a. MoDTC / PFM combination had a positive effect in reducing friction in a steel – steel contact but the level of wear protection was not improved relative to the reference oil. Both the friction and wear performance were dominated by MoDTC.
b. MoDTC / PFM combination gave the lowest friction in a sp2 ;Cr ;Cr
doped; 0% hydrogen DLC ball – steel disc contact and resulted in significantly lower wear of the DLC coating. With sp2
doped; 0% hydrogen DLC there appears to be a synergistic effect between the inorganic FM and the polymeric FM, as the friction and wear results were significantly improved compared to either of the two individual friction modifiers.
c. MoDTC + PFM combination did reduce friction in a sp2 ; 15%
hydrogen DLC ball – steel disc contact to a level similar to that of MoDTC by itself but the time to reach the minimum was longer due to the presence of the PFM. Whilst having a negative influence on the initial friction reduction, the PFM did provide an increase in wear protection of the DLC surface from MoDTC erosion but it did not reach the level of protection provided by the PFM alone.
40 LUBE MAGAZINE NO.139 JUNE 2017
LINK
www.crodalubricants.com
4. Conclusions
1. DLC type has a very important role to play in influencing friction and wear and friction modifier selection:
- H-free sp2 - sp2
presence of MoDTC /sp3
type responds very well to GMO but not in the H-containing DLCs respond positively to polymeric
type FMs, even in the presence of MoDTC
- No single FM is optimal for all DLC – Fe and all Fe – Fe contacts, compromises may be required
- PFMs alone can provide excellent friction and wear performance on DLC surfaces
2. PFMs and MoDTC can act synergistically
3. Low friction can be associated with high wear, especially with MoDTC
4. Optimisation of MoDTC / PFMs / Add Packs could yield greater improvements in DLC contacts (friction and wear)
John Eastwood
Head of Global Business Development ©
Croda Europe Ltd 2017. All rights reserved.
No.110 page 8
d. MoDTC / PFMs did provide a reduction in friction in a 50% sp3
; 40% hydrogen DLC ball – steel disc contact and provided a high level of wear protection, similar to that provided by PFM alone.
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