24th International Colloquium Tribology - January 2024 203 Investigtion of Functional Lubricity of Water-Based MWFs by an Innovative Tool Ameneh Schneider, Felix Zak Optimol Instruments Prueftechnik GmbH, Munich/ Germany Motivation: The coolant system for metal working is a typical example of a tribomechanical system, where several wear mechanisms are present simultaneously. Additionally formulation of MWFs must meet many challenges such as: Environment, Health and Safety, Corrosion, Staining, Formulation Stability, Foaming, Fluid Longevity. Particulate composition varies significantly depending on the cutting process and operating conditions, as well as coolant characteristics and coolant systems. 2002 the autors mentioned that the workpiece (and its relative machinability) and tool materials can vary greatly, and there are a multitude of different machining processes (milling, drilling, grinding, broaching, etc.), each with their own fluid needs [1]. 20 years later in 2022 the authors [2] mentioned also that the greatest challenge is the machining of ferrous and non-ferrous alloys with a single MWF. The complex fluids can be mineral oil based, synthetic based, semisynthetic or water based (emulsion). Big challenge will be to find the right type of AWand EP-additive to work on ferrous and non-ferrous alloy. For example, a positive additive effective on a ferrous alloy may be antagonistic to a non-ferrous alloy and visa versus. For these reasons measuring the tribological performances of different formulated will give more insides about the lubricity and protection performances of MWFs. Optimol Instruments developed a new setup in cooperation with his industry partners for meeting these challenges and help this MFWs manufacturers to develop high performance coolants and MWFS for future, Design of set up for fluids with high flow rates and high rotary velocities for SRV ® rotation modus: Figure 1 shows a cross section of new set up. The fluid will be supplied directly into the contact area by using a nozzle element. Secondly it is possible to add an addition temperature sensor in fluid drain. Through using this setup in the rotation modus of SRV ® high rotation speeds up to 2000 rpm are achievable. Figure 1: Gross section of construction design The designed is very user friendly as can be seen in Figure 2. Lower disk specimens, fluid bath, different holders for variable contact geometry (point, line, area) and fluid pump are included in this setup. Figure 2: New MWF-Set up in the test chamber of SRV ® rotation modus. Experimental part: The functionality of new device was proved by 42 tests. Various specimens’ combination for three different fluid composition (Coolant A. B, C) were chosen. All fluids were prepared as 6% water emulsion. 4 different materials as a mushroom-shaped specimen - as tool piece were available for this study: • 20MnCr5 (Gear steel) • 16MnCr5 (Higher wear protection) • 115CrV3 (Tool steel) • X8CrNiS18-9 (Stainless steel) Following two materials as work pieces were selected for this investigation: • 16MnCr5 untampered, E-Module: 208 [kN/ mm²] • Aluminum alloy AlMg3, E-Module: 70 [kN/ mm²] 204 24th International Colloquium Tribology - January 2024 Investigtion of Functional Lubricity of Water-Based MWFs by an Innovative Tool The temperature changes for the disk as well as for the fluids were registered for all test combinations. After some pretests and discussions with 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 Repeatability of results concerning friction and wear value were evaluated. Example of results Figure 3 shows the values of coefficient of friction (CoF) during the test time for one fluid (Coolant C) in material combination steel and 15MnCr5. Each test combination was repeated once. The repeatability of results was very good. The online measurement of wear was also possible however the wear values at the tool material at the end of the test is the most import one and the values war repeatable as well. Figure 3: repeatability of CoF value for coolant C As the repeatability for all tests was very good the ranking of three fluids, regarding their tribological performances was easily possible. The CoF curves for each coolant for material combination steel and 20MnCr5 is compered in Fig. 4. Coolant C delivered the lowest and most stable values during the entire test time. 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 as a balk diagram in Figure 5: Figure 5: Mean CoFand wear values (last 15 min + standard deviation) for Steel For all material pairing the coolant C have shown the best tribological performances followed by coolant B and A. Optimizing of speed and other test parameters such as normal load for aluminum is carried on by Optimol Instruments for these three and many other fluids. The results are ongoing and will be presented in future publications. Summary: For Steel as workpiece • A good differentiation in performances can be shown for all selected material pairings with this new setup. • Repeatability of results is very good. • Temperature developments during the tests for disk and coolants are stable: • + 1 to 2-°C due to good cooling effects • Online wear measurements work precisely. This new MWF setup for SRV ® rotation modus enables the formulators to identify, try and confirm and finally find the best MWF for multi-metal application. Additionally, it helps to solve the upcoming challenges such as improved economic efficiency of manufacturing processes by using more efficient formulations for extending the tool life. References: [1] Radoslav Rakic et al, The influence of the metal working fluids on machine tool failures; Wear, Vol. 252 (2002), Iss. 5-6, Pages 438-444. [2] Neil Canter, Metalworking fluids: Current options for machining multi-metal alloy, TLT magazine March 2022, Pages 44-54. Corresponding author: ameneh.schneider@optimol-instruments.de www.optimol-instruments.de