Lubricant Additives

206 Lubricant Additives: Chemistry and Applications

Ring roughness, Ra, was ∼0.15 μm, although the cylinder was very smooth. Hence, the rough-
ness of the ring determined the shape of the Stribeck curve, specifi cally the BL/ML transition. The
load (normal force Fn = 100 N) was chosen such that heat development in the contact zone was
negligible, so that the viscosity was constant. Hence, it was possible to determine the Stribeck curve
only as a function of speed. The temperature chosen was 40 ̊C.
The following graph (Figure 7.10) shows comparative data for RL 179/2 as well as this oil with
addition of 0.5% GMO and addition of 0.5% of organic FMs A and B. (A and B are products with
both free and esterifi ed hydroxyl groups.)
All the FMs studied here show a signifi cant reduction of the friction coeffi cient in the BL
regime. Organic FMs A and B show a reduction in the mixed regime as well. On fi rst sight this
looks favorable.
The next graph (Figure 7.11) shows the wear, taken at similar sliding distances.

0.16

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.00

0.010 0.100 1.000 10.000

Contact speed v (m/s)

RL 179/2 (5W/30) + 0.5% GMO + 0.5% OFM A + 0.5% OFM B

Friction coefficient

f (

−)

FIGURE 7.10 Stribeck curves of CEC RL 179/2 plus organic FMs.

9.000

8.000

7.000

6.000

5.000

4.000

3.000

2.000

1.000

0.000

Wear area

RL179/2 + 0.5% GMO + 0.5% OFM A + 0.5% OFM B

Wear scar (mm

2 )

FIGURE 7.11 Wear scars of CEC RL 179/2 plus organic FMs.