Friction

, Volume 2, Issue 2, pp 193–208

Surface passivation and boundary lubrication of self-mated tetrahedral amorphous carbon asperities under extreme tribological conditions

  • Pedro A. Romero
  • Lars Pastewka
  • Julian Von Lautz
  • Michael Moseler
Open Access
Research Article

DOI: 10.1007/s40544-014-0057-z

Cite this article as:
Romero, P.A., Pastewka, L., Von Lautz, J. et al. Friction (2014) 2: 193. doi:10.1007/s40544-014-0057-z

Abstract

Tetrahedral amorphous carbon coatings have the potential to significantly reduce friction and wear between sliding components. Here, we provide atomistic insights into the evolution of the sliding interface between naked and hydrogen-passivated ta-C sliding partners under dry and lubricated conditions. Using reactive classical atomistic simulations we show that sliding induces a sp3 to sp2 rehybridization and that the shear resistance is reduced by hydrogen-passivation and hexadecane-lubrication—despite our finding that nanoscale hexadecane layers are not always able to separate and protect ta-C counter surfaces during sliding. As asperities deform, carbon atoms within the hexadecane lubricant bind to the ta-C sliding partners resulting in degradation of the hexadecane molecules and in increased material intermixing at the sliding interface. Hydrogen atoms from the passivation layer and from the hexadecane chains continue to be mixed within a sp2 rich sliding interface eventually generating a tribo-layer that resembles an a-C:H type of material. Upon separation of the sliding partners, the tribo-couple splits within the newly formed sp2 rich a-C:H mixed layer with significant material transfer across the sliding partners. This leaves behind a-C:H coated ta-C surfaces with dangling C bonds, linear C chains and hydrocarbon fragments.

Keywords

Atomic-scale simulations DLC lubrication hexadecane passivation sliding mixed layer wear 

Copyright information

© The author(s) 2014

This article is published under license to BioMed Central Ltd. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited

Authors and Affiliations

  • Pedro A. Romero
    • 1
  • Lars Pastewka
    • 1
    • 2
  • Julian Von Lautz
    • 1
  • Michael Moseler
    • 1
    • 3
    • 4
  1. 1.Fraunhofer Institute for Mechanics of Materials IWMFreiburgGermany
  2. 2.Karlsruhe Institute of TechnologyIAM-ZBSKarlsruheGermany
  3. 3.Freiburg Materials Research CenterFreiburgGermany
  4. 4.Physics DepartmentUniversity of FreiburgFreiburgGermany

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