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Tribological behavior of WC-DLC-WS2 (WCS) nanocomposite coatings

Wu, Jianhui
http://rave.ohiolink.edu/etdc/view?acc_num=osu1094675462

Abstract Details

2004, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
The dry sliding behavior of diamond-like carbon (DLC) based nanocomposite coatings has been examined in different environments, ranging from vacuum, high-purity nitrogen to ambient air using 440C stainless steel sliders. The test geometry of pin-on-disk allowed convenient collection of wear debris, measuring of the friction force and, using a Kelvin probe, in situ detection of structural and chemical changes incurred on wear tracks. It was found that WCS composite coatings have excellent tribological characteristics in all test environments, including low friction coefficient, negligible wear rate and extended lifetimes. Post-test characterization included TEM, Raman spectroscopy, SIMS, XPS, SEM and EDS. Examination of worn wear track and pin surfaces, cross-sections and debris confirmed the importance of mixing, material transfer and environmental interactions. Mixed components dominate the sliding behavior of WCS coatings. A single graphitic carbon or WS2 protective lubricating layer has not been found on wear tracks or pin surfaces. Instead, both components were identified to be present together in varied amounts depending upon the testing environment and loading. Thus, the lubrication mechanisms involved in different environments are far more complex than what has been reported previously. Synergistic effects contributed by both graphitic carbon and WS2 account for the extremely low frictional behavior of WCS coatings during dry sliding. Molecular dynamics (MD) calculations were implemented to simulate the behavior of soft and/or hard particles in a 2D 3-component composite system interacting via Lennard-Jones potentials. Sliding results showed that soft particles tended to mix with the base materials, and with increased sliding speed mixing proceeded even faster. The mixed materials formed a confined “weakened” zone at the sliding interface, where shear remained localized after a steady state was achieved. For the case of sliding of composites with hard particles, the particles tended to agglomerate to minimize the work done during sliding simulations. There was a transient period before the friction coefficient reached an averaged steady state value, the value of which decreased with increased sliding velocity. A single uniform interfacial layer due to sliding was not observed in the simulations. This is consistent with experimental results. Formation of an interfacial mixed layer is responsible for shear localization and achievement of steady state friction. The temperature distribution profile suggests that heat generated in the sliding interface region conducts to the reservoirs by one-dimensional heat flow, consistent with Fourier’s Law for heat conduction.
David Rigney (Advisor)
188 p.
Engineering, Materials Science
sliding; DLC; COATINGS; wear tracks; friction; WCS; Raman

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Citations

  • Wu, J. (2004). Tribological behavior of WC-DLC-WS2 (WCS) nanocomposite coatings [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1094675462

    APA Style (7th edition)

  • Wu, Jianhui. Tribological behavior of WC-DLC-WS2 (WCS) nanocomposite coatings. 2004. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1094675462.

    MLA Style (8th edition)

  • Wu, Jianhui. "Tribological behavior of WC-DLC-WS2 (WCS) nanocomposite coatings." Doctoral dissertation, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1094675462

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.