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Advances in Tribology
Volume 2012, Article ID 923818, 7 pages
Research Article

Dependence of Pin Surface Roughness for Friction Forces of Ultrathin Perfluoropolyether Lubricant Film on Magnetic Disks by Pin-on-Disk Test

1Mechanical Engineering Department and High Technology Center, Kansai University, Osaka 564-8680, Japan
2Nagoya Industrial Science Research Institute, Nagoya 464-0819, Japan
3Department of Research and Development, Nomura Plating Co., Ltd., Osaka 555-0033, Japan

Received 14 August 2012; Accepted 4 December 2012

Academic Editor: Tom Karis

Copyright © 2012 H. Tani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We fabricated supersmooth probes for use in pin-on-disk sliding tests by applying gas cluster ion beam irradiation to glass convex lenses. In the fabrication process, various changes were made to the irradiation conditions; these included one-step irradiation of Ar clusters or two-step irradiation of Ar and N2 clusters, with or without Ar cluster-assisted tough carbon deposition prior to N2 irradiation, and the application of various ion doses onto the surface. We successfully obtained probes with a centerline averaged surface roughness that ranged widely from 1.08 to 4.30 nm. Using these probes, we measured the friction forces exerted on magnetic disks coated with a molecularly thin lubricant film. Perfluoropolyether lubricant films with different numbers of hydroxyl end groups were compared, and our results indicated that the friction force increases as the surface roughness of the pin decreases and that increases as the number of hydroxyl end groups increases.