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a material combination of steel and 15MnCr5. Each test combination was repeated once. The repeatability of results was found to be very good. The online measurement of wear was also possible, however the wear values of the tool material at the end of the test is the most important factor.
Figure 2: New MWF-Set-up in the test chamber of SRV® Experimentation
The functionality of the new device was proven over the course of 42 tests. Various specimens were combined to produce the three different fluid compositions (Coolant A, B and C) that were chosen. All fluids were prepared as 6% water emulsions.
Four different materials were tested as a mushroom- shaped specimen – as a tool piece of this shape was available for this study: • 20MnCr5 (Gear steel). • 16MnCr5 (Higher wear protection). • 115CrV3 (Tool steel). • X8CrNiS18-9 (Stainless steel).
The following two materials as workpieces were selected for this investigation: • 16MnCr5 untampered, E-Module: 208 [kN/mm²]. • Aluminium alloy AlMg3, E-Module: 70 [kN/mm²].
The temperature changes for the disk as well as for the fluids were recorded for all test combinations.
After some pre-tests and discussions with the industry partner, the following test parameters were chosen: • Normal load: 150 N. • Rotation speed: ramp 0 to 3.14 m/s in 10 min. • Temperature: RT. • Test time: 30 min.
The repeatability of results concerning friction and wear value were evaluated.
Examples of results Figure 3 shows the values of the coefficient of friction (CoF) during the test time for one fluid (Coolant C) in
Figure 5: Mean CoF- and wear values (last 15 min + standard deviation) for steel.
Continued on page 27 LUBE MAGAZINE NO.174 APRIL 2023 25 Figure 4: Comparison of CoF for three fluids.
Mean CoF and wear (last 15 min + standard deviation) for steel with all other 4 tool materials are presented in Figure 5:
Figure 3: repeatability of CoF value for coolant C.
As the repeatability for all tests was very good, the ranking of the three fluids regarding their tribological performances was easily possible. The CoF curves for each coolant for material combinations of steel and 20MnCr5 is compared in Figure 4. Coolant C delivered the lowest and most stable values during the entire test time.
rotation modus.
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