A Guide to Pin on Disk Tribometers

The MFT5000 is a Universal Tribometer from Rtec Instruments. It is a multi-functional tribometer with the ability to carry out various wear and friction tests on the same platform. It also has the potential to carry out ASTM, DIN, ISO, and non-standard tribology tests. The tribometer is equipped with modules that are easy to interchange, thereby enabling it to perform different tests on the same platform.

In this article, a rotary module is used to run a common friction and wear test. The test helps in determining friction, coefficient of friction (COF), wear, rate of wear, volume of wear, and wear resistance. The test can be applied to liquid, materials, lubricants and coatings. The test can be run under a broad range of rotational speed, load, temperature, and sliding speed.

Friction and Wear Test Samples

Since two specimens are required for tribology tests, in this case, a pin or ball is positioned perpendicular to a flat circular disk. The samples are mounted using the universal upper and lower sample holders. Common test specimens are 100Cr6 steel ball with a diameter of 10 mm, or 6.3-mm stainless steel pin and 100Cr6 disk. The surface flatness and roughness of both the materials are highly crucial in achieving repeatable results.

Pin-on-Disk Test Method

The stationary pin or ball is made to press against the rotating disk by the tribometer. The friction force, COF, wear volume, wear rate, temperature, and various other tribology parameters are measured during the test. The machine configuration for pin-on-disk wear testing is perfect for the characterization of tribological properties of polymers, alloys, coatings, ceramics, solid lubricants, metals, and so on. The figure below illustrates the test setup under dry conditions.

pin-on-disk test method

The below figure shows the setup in lubricated conditions, where the samples are submerged in the lubricant. The Rtec tribometer can be used to configure such setups at room temperature, or at a broad temperature range of −120 to 1000 °C.

pin-on-disk test method

Analysis

pin on disk analysis

The figure above illustrates the ball wear mark following the test.

comparison of COF in pin on disk

The above figure illustrates the comparison of coefficient of friction with respect to time for four specimens under same rotation speed and load against a Cr6 ball with a diameter of 10 mm diameter at 200 °C. The coating on Sample 1 rapidly breaks, and Sample 2 exhibits low friction throughout the test. Such tests can be performed at room temperatureor at high temperatures using the MFT platform.

Automatic Inline Imaging—Roughness, Wear, Volume vs Time

The Rtec multi-functional tribometer is equipped with a patented inline 3D Profilometer, which has the ability to automatically measure the surface topography of the wear track at intervals predefined by the user, for instance, after a duration of time, a specific number of cycles, or at the start of an event such as increase in friction. Advanced encoders are equipped in the XY stage for automatically moving the sample between the test and image area. The analyses are highly robust due to the potential for quantifiable characterization of the change in wear track and surface topography with time and integrating it with friction data.

The initial 3D image obtained with the help of the profilometer also enables the grain boundaries and machining marks to be taken into account and can be helpful in explaining the stick slip, difference in friction, wear, and so on between the specimens. The figure below illustrates the wear mark developed versus time for an alloy steel sample as part of a ball-on-disk test for a duration of 75 minutes.

automatic inline imaging

The figure also illustrates the friction data with respect to the time stamp. It also points out the time point at which the surface images were captured at the time of the test. The data evidently shows that the test stops and starts from the same location.

automatic inline imaging

The figure above depicts the 3D images of surface wear versus time/test step. The wear, friction, and image correlation are highly robust information produced automatically.

Conclusion

The MFT5000 rotary module is a great choice to perform tests in pin/ball-on-disk mode. It is possible to run the tool under dry or lubricated conditions with options to perform the tests at higher temperatures. High contact pressure for appropriate samples can be achieved by applying high loads of up to 5000 N. These tests can be performed under liquid media with the help of the anti-splash containers. The tester is transformed into a highly robust tool in the hands of the QC engineer or researcher by the inline profilometer:

  • The test can be operated from −120 to 1000 °C
  • Wide loads from a few milli Newtons up to 10,000 N can be applied to realize desired contact pressure
  • The tool can be run under dry or lubricated conditions
  • Surface change can be quantified with respect to time with the help of the inline profilometer
  • The tests can be performed under liquid media with the help of the high-speed anti-splash containers

All the above-mentioned aspects render this tester a highly robust tool for the QC engineer or the researcher.

This information has been sourced, reviewed and adapted from materials provided by Rtec-Instruments.

For more information on this source, please visit Rtec-Instruments.

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