Speaker
Description
Triboscopy is the numerical imaging of the evolution of a tribosystem and combines local and time-resolved information, most often the evolution of friction. We further developed triboscopic imaging for identifying wear mechanisms in tetrahedral amorphous carbon coatings (ta-C) during dry friction. Based on this approach we demonstrate the additional analytical opportunities enabled by this technique compared to conventional friction curves and wear track images.
ta-C coatings have been shown to exhibit exceptionally low friction and wear under dry sliding in the presence of water vapor as well as acceptably low friction and wear in the presence of inert gases. However, these properties deteriorate rapidly under vacuum conditions with decreasing pressure.
The methodology is based on measurements which were carried out with a custom-built ultra-high vacuum tribometer in ball-on-disc configuration with 1 kHz logging rate. The environments used were dry and humid air, nitrogen, and vacuum up to 10 8 mbar. The transformation of the raw measurement data to the triboscopic images was performed with a custom Python program. The carbon coatings used ranged from a-C to ta-C and were prepared by Laser-Arc-PVD.
All features present in the resulting images were identified and classified by their persistence regarding position in the track and wear duration. From the analysis four classes were defined: uniform, random, cycle-persistent, and position-persistent. This classification permitted to distinguish different wear mechanisms. For example, “random” spikes in friction could be attributed to debris in the contact from the abrasion. Additionally by evaluating the absolute value of the acceleration, high deceleration and acceleration were observed that can be attributed to a stick and slip behavior.
This work was supported by the Deutsche Forschungsgemeinschaft (DFG – German Research Foundation) under grant agreement 415726702.
| Speaker Country | Germany |
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