In Situ Studies of Wear Mechanisms in Magnetic Thin-Film Disks

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Abstract
Contact start-stop (CSS) tests and continuous drag tests are used for detailed in situ analysis of wear mechanisms in magnetic thin-film rigid disks. Coefficient of static friction and disk surface reflectance are measured during the contact start/stop tests and coefficient of kinetic friction, acoustic emission rms, acoustic emission count, and disk surface reflectance are all measured during the continuous drag tests. It is the first time that friction, acoustic emission and optical reflectance sensors are used simultaneously for wear studies. In situ measurements are used to determine precursors to failure of magnetic thin-film disks, to compare wear processes in CSS and drag tests, and to correlate CSS and drag tests. Disk wear is seen to follow a pattern of lubricant depletion and/or localized polishing of overcoat asperities. The sliding distance associated with CSS tests is less damaging to disks than continuous drag sliding distances. A combination of sensors used in this study, in particular an optical sensor used to measure changes in disk reflectance, has been demonstrated to be valuable in understanding the failure mechanisms.