Abstract
In tribo-systems, tribological behavior is influenced by a combination of several mechanisms. Among them, plastic deformation mechanisms (PDMs) and tribo-chemical reactions (TCRs) are particularly significant. The article explores the role of these fundamental mechanisms during the dry sliding of a Ti6Al4V-pin against an SS316L disk. PDM was controlled by changing the sliding speed (0.01–1.5 ms−1). To explore the interdependence of TCR submechanisms, namely, the formation of a mechanically mixed layer (MML) and tribo-oxidation, the pin diameter was varied (2.1, 4.6, and 6.6 mm) while maintaining a constant vacuum environment and contact pressure. At low sliding speeds (0.01–0.3 ms−1), the high wear-rate and coefficient of friction (CoF) are due to the dominance of PDM, enabled by adiabatic shear banding (ASB). Within the sliding speed range of 0.3–0.7 ms−1, a durable and wear-resistant MML forms on the pin surface incorporating Fe transferred from the disk. As the MML attains its highest stable thickness (≈51 µm at 0.7 ms−1), the lowest values of wear-rate (18.15 × 10−4 mm3/Nm) and CoF (0.324) are observable. Above 0.7 ms−1, thermally induced phase transformation-assisted material softening leads to a substantial increase in wear-rate and CoF. The case is otherwise for the smallest pin (2.1 mm) sliding at 1.5 ms−1. As sliding speed increases, wear transitions from adhesion to mild abrasion and then to severe adhesion.
