| AVS 61st International Symposium & Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR+NS-ThM |
| Session: | Bridging Scales in Tribology |
| Presenter: | Lars Pastewka, Karlsruhe Institute of Technology, Institute for Applied Materials IAM, Germany |
| Correspondent: | Click to Email |
Diamond and amorphous carbon (aC) are prototypical examples of wear resistant materials. Yet, these materials wear down, but little is known about the atomic scale processes that cause wear. Molecular dynamics is ideally suited to gain a deeper understanding of the underlying wear processes [1]. Such atomic-scale simulations reveal that both, mechanical and oxidative wear actions are active. Mechanical action transforms the material to a weaker state that is then easily oxidized. For diamond, we find a transition to an aC, while we find a high-density—low-density aC-aC transition for amorphous thin films. The velocity of the diamond/aC interface depends crucially on the diamond surface orientation with the highest speed found for (110) surfaces that are rubbed in the (001) direction, while the lowest interface speed was observed for the diamond (111) surface. High-density aC itself transforms even faster to a low density state that then succumbs to wear [2]. We relate the aC-aC transition to shear-banding in plasticity of amorphous materials, and argue that the formation of shear-bands is crucial for the wear resistance of carbon based hard coating. These findings are in perfect agreement with a 600 years old experimental knowledge of diamond polishers, and with recent experiments comparing wear in diamond and amorphous carbon thin films.
[1] L. Pastewka, S. Moser, P. Gumbsch, M. Moseler, Nat. Mater. 10, 34 (2011)
[2] T. Kunze, M. Posselt, S. Gemming, G. Seifert, A.R. Konicek, R.W. Carpick, L. Pastewka, M. Moseler, Tribol. Lett. 53, 119 (2014)