Advantages of Using Triboscopic Imaging: Case Studies on Carbon Coatings in Non-Lubricated Friction Conditions

Triboscopy focuses on the analysis of the temporal evolution of a tribological system, combining local and time-resolved information, most commonly the evolution of friction. In this work, this technique is applied on measurements, which were carried out with a custom-built ultrahigh vacuum tribometer in ball-on-disc configuration. Based on these experiments, an extended classification to distinguish different triboscopic features is suggested, depending on the persistence in both track position and time: UNIFORM, GLOBAL, LOCAL, and SPORADIC. Further, a filter technique for quantifying triboscopic data regarding this classification is introduced. The new and improved triboscopic techniques are applied to various dry friction measurements of hydrogen-free carbon coatings under varying humidity and pressure. The resulting specific triboscopic features are correlated to wear phenomena, such as counter body coating abrasion, inhomogeneities in the wear track, non-uniform track wear, stick-slip and debris in the contact area, demonstrating the increased analysis and monitoring capabilities when compared to conventional friction curves and wear track images.