In fact, this modern tribometer supports the end-user in the following fields: • Simulation of friction and wear processes under mixed/boundary or unlubricated conditions
• Quality assurance of lubricants and materials in production
• Fundamental research in material and tribology
Over 30 different holder and adapter combinations have been designed and produced until now. This versatility corresponds to real parts and contact geometries on different tribological fields. By adjusting the parameters (e.g. specific pressure, temperature, velocity, etc.) this modern tribometer enables the user to simulate closely the real application in the laboratory. A few examples will give an overview of how modern tribotesting can make the development process of industrial lubricants more effective by prescreening products in the stage of development, before examining them on a conventional test bench or in the field.
Prescreening during formulation procedure 1. Prescreening of Hydraulic oils: The prescreening method is based on evaluation of friction, wear and extreme pressure properties by using the existing SRV®
standard methods:
ASTM D7421 “Standard Test Method for Determining Extreme Pressure Properties of Lubricating Oils Using High-Frequency, Linear-Oscillation (SRV® Machine”
) Test
ASTM D6425-11/DIN 51834-2:2010 “Standard Test Method for Measuring Friction and Wear Properties of Lubricating Oils Using SRV® Test Machine” ASTM D7755
“Standard Practice for Determining the Wear Volume on Standard Test Pieces Used by High-Frequency, Linear-Oscillation (SRV® Machine”
Figure 3. Result of standard test ASTM D7421
Based on many evaluated data the following criteria for SRV®
are suggested as prescreening for Vickers
pump test: • Extreme pressure D7421-11 - Set limit: >900 N (P0max.~ 3,017 MPa)
• Anti-wear properties D6425-11/DIN 51834-2:2010 (FN= 300 N (~FZG >14) - ball < 3.5 10-9 mm³/N·m - disk < 2.0 10-9 mm³/N m
• Light microscopic investigation of the wear tracks (flat disk) in order to observe adhesive mechanisms
2. Prescreening of gear oils
Another application-oriented bench test is the FZG loaded gear test. The motivation was to develop a quick and cost-effective prescreening method for gear lubricants and associated additive packages which can be used as easy screening test of new alloys and coatings as well. Figure 3 shows the configuration of the special setup for testing gear oils, developed by Optimol Instruments.
Lower specimen: Standard SRV® disk with a diameter
of 24 mm and a height of 7.9 mm, out of 100Cr6 rolling bearing steel. The surface must be lapped with Ra 0.05 µm.
) Test
Test results of testing the load carrying capacity of 4 different hydraulic oils according to ASTM D7421 is shown exemplary in Figure 3.
Upper specimen: A cylinder (6mm x 8mm) which has a crowned profile with a supporting length of 4mm and polished surface. The body is declined with an angel of 10°.
Figure 4. Specimen configuration Continued on page 28 LUBE MAGAZINE NO.144 APRIL 2018 27
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