Journal of the Korean Physical Society

Korean Physical Society (한국물리학회)
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Effects of Humidity on the Friction Coefficient of Diamond-Like Carbon (DLC) Coating

Kim, Sang-G.;Cho, Yong-K.;Jang, Woo-S.;Kim, Sung-W.;Nagahiro, Saito;Takai, Osamu

  • Published : 20090300
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Abstract

A diamond-like Carbon (DLC) coating has been known to be a good tribological problem solver due to its low friction characteristics and high hardness. The friction coefficient values shown in the literature surveyed differ from the authors' due to different test conditions. When we plot these results and our own with the variable of humidity, the friction coefficient decreases with increasing environmental humidity. By using contact angle measurements to study the interface properties of these coatings, we conclude that this change comes from the hydrophilic and the hydrophobic properties of the surface and the eventual change of the wear mode. DLC films were deposited on SKD11 steel by using pulsed (DC PECVD) (a-C:H, hydrogenated DLC, Si-containing DLC) and amorphous carbon filtered arc DLC (a-C, non-hydrogenated DLC). Deposited DLCs were tested according to humidity by using a tribometer. We used a SUJ2 (JIS standard) steel ball bearing for the counterpart of wear test. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and surface roughness testers were used for surface analysis of the DLC and the wear trace. The Raman spectra of the films showed that the carbon bonding structures changed according to the I(D)/I(G) intensity ratio for the wear trace at severe wear conditions. In normal humidity, 30 $\sim$ 85 % RH, the DLC had a friction coefficient lower than it did in 5 % RH. In this case, the Si-containing hydrogenated DLC definitely had the lowest friction coefficient. Eventually, it also had the lowest contact angle, as expected. When we investigated two different kinds of DLCs in terms of hydrogen content, we observed the same effect of relative humidity on friction behavior.

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References

  1. A. Erdemir, Tribology Int. 38, 249 (2005) https://doi.org/10.1016/j.triboint.2004.08.008
  2. Y. S. Jeon, Y. S. Park, H. J. Kim, B. Y. Hong and W. S. Choi, J. Korean Phys. Soc. 51, 1124 (2007) https://doi.org/10.3938/jkps.51.1124
  3. K. Oguri and T. Arai, Surf. Coat. Tech. 47, 710 (1991) https://doi.org/10.1016/0257-8972(91)90344-V
  4. K. Oguri and T. Arai, Thin Solid Films 208, 158 (1992) https://doi.org/10.1016/0040-6090(92)90635-O
  5. W.-J. Wu, T.-M. Pai and M.-H. Hon, Dia. Rel. Mat. 7, 1478 (1998) https://doi.org/10.1016/S0925-9635(98)00213-1
  6. W.-J. Wu and M.-H. Hon, Surf. Coat. Tech. 111, 134 (1999) https://doi.org/10.1016/S0257-8972(98)00719-1
  7. S. S. Camargo, Jr., A. L. Baia Neto, R. A. Santos, F. L. Freire, Jr., R. Carius and F. Finger, Dia. Rel. Mat. 7, 1155 (1998) https://doi.org/10.1016/S0925-9635(98)00165-4
  8. H. Mori and H. Tachikawa, Surf. Coat. Tech. 149, 225 (2002)
  9. J. C. Damasceno and S. S. Camargo, Jr., Thin Solid Films 516, 1890 (2008) https://doi.org/10.1016/j.tsf.2007.10.119
  10. M. Saraiva, C. Louro, A. Cavaleiro and N. J. M. Car-valho, Traitement Thermique 386, 45 (2008)
  11. Y. H. Cho, Y. S. Park, H. J. Cho, B. Y. Hong and W. S. Choi, J. Korean Phys. Soc. 51, 1129 (2007) https://doi.org/10.3938/jkps.51.1129
  12. M. Grischke, A. Hieke, F. Morgenweck and H. Dimigen, Dia. Rel. Mat. 7, 454 (1998) https://doi.org/10.1016/S0925-9635(97)00237-9
  13. R. L. DeRosa, P. A. Schader and J. E. Shelby, J. Of Non-Cryst. Sol. 331, 32 (2003) https://doi.org/10.1016/j.jnoncrysol.2003.08.078
  14. D. Neerinck, P. Persoone, M. Sercu, A. Goel, D. Kester and D. Bray, Dia. Rel. Mat. 7, 468 (1998) https://doi.org/10.1016/S0925-9635(97)00201-X