AVS 52nd International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuM

Paper SE-TuM10
Tribological Behavior and Thermal Stability of TiC/a-C:H Nanocomposite Coatings

Tuesday, November 1, 2005, 11:20 am, Room 201

Session: Hard Coatings and Wear Mechanisms of Protective Coatings
Presenter: Y.T. Pei, University of Groningen, The Netherlands
Authors: Y.T. Pei, University of Groningen, The Netherlands
D. Galvan, University of Groningen, The Netherlands
J.Th.M. De Hosson, University of Groningen, The Netherlands
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Advanced TiC/a-C:H nanocomposite coatings have been produced via reactive deposition in a closed-field unbalanced magnetron sputtering system (Hauzer HTC-1000). These wear-resistant coatings are targeted for automotive applications where high-load bearing capacity, low friction and wear rate are the primary requirements. In this paper, the tribological behavior of the nanocomposite coatings is scrutinized by means of ball-on-disc tribo-tests in the temperature range of 20-400°C and in different environments, in conjunction with detailed examinations of the mechanical properties. The influence of the volume fraction and grain size of TiC nanocrystallites on the coating properties has been examined. The thermal stability of the coatings in terms of critical temperatures, at which the degradation of wear resistance and friction of the coatings starts, are monitored in comparison with the variation of hardness and elastic modulus of the coatings with temperature. In-situ monitoring the thickness of transfer films formed on the counterpart (100Cr6 ball) reveals that the dynamic and super-low friction (µ=0.01-0.05 in air) behavior is directly related to the thickening of transfer films that contributes self-lubrication. The lowest friction and wear rate are obtained when the size of TiC particles become of the same dimension as the separation distance of amorphous hydrocarbon matrix, maximizing also the toughening effects in the composite system. These phenomena have been understood based on a physical model.