Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE 2.2 DLC 50% sp3 ; 40% hydrogen Ball – Steel Disc
The 5W30 ACEA C3 reference oil is a high friction oil (coefficient of friction 0.11 in the boundary regime - figure 9) but resulted in only a small amount of wear (figure 10) on both the 50% sp3 40% hydrogen DLC ball (4000 µm3
; ) and steel disc (12,600 µm3 ).
The combination of GMO and MoDTC resulted in a moderate decrease in wear on the 50% sp3
; 40%-H DLC ball and a
significant decrease in wear on the steel disc compared to that observed for the oil containing only MoDTC (figure 11). MoDTC drastically increased disc wear compared to the 5W30 reference oil alone which was 12,600 µm3
. Figure 9. Stribeck Curves for 50% sp3 ; 40% hydrogen DLC Ball – Steel Disc Figure 11. Addition of GMO to MoDTC, effect on wear volume
The most effective friction modifiers for this particular DLC – steel arrangement were the polymeric friction modifiers. Whilst PFMs did not demonstrate any significant friction reducing properties at very low speed, they did provide the lowest friction in the mixed lubrication regime.
Used alone, PFMs reduced the wear on the 50% sp3 DLC ball by 90% and by >50% on the steel disc (figure 12).
; 40%-H
No.110 page 4
Addition of GMO to the oil containing MoDTC resulted in a blend with a similar friction profile to the reference oil + 0.5% GMO, that is, slightly higher in the boundary regime but lower than MoDTC in the mixed lubrication regime.
Figure 10. Stribeck Curves for 50% sp3
; 40% hydrogen DLC Ball – Steel Disc
Introducing 0.5% MoDTC into the formulation resulted in a decrease in friction (0.09) in the speed range of 0.1m/s – 0.03 m/s. However, wear on the 50% sp3 (10,000 µm3 (70,000 µm3
; 40% hydrogen DLC ball
) increased by 150% and by 450% on the steel disc ) due to the presence of MoDTC.
Figure 12. PFM1, reduction of wear volume
Glycerol mono-oleate at a treat-rate of 0.5% also provided a reduction in friction (0.10) compared to the 5W30 reference oil. It also proved to be lower in friction than the MoDTC containing oil at higher entrainment speeds (>0.1m/s). Whilst the wear volume of the steel disc (5300 µm3 the wear on the 50% sp3
) was decreased by >50%, ; 40% hydrogen DLC ball (6700 µm3
increased by almost 70% relative to the reference oil but was much lower than the oil containing MoDTC (70,000 µm3
). 36 LUBE MAGAZINE NO.139 JUNE 2017 )
Figure 13 shows that a combination of MoDTC and PFMs, together acted to reduce the wear on both the DLC ball and the steel disc by more than 80%, a considerable achievement given that MoDTC alone actually caused wear to increase on both the 50% sp3
; 40% hydrogen DLC ball and steel disc.
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