Comparisons of Friction Characteristics of a Lightly Loaded Pin Sliding Over Magnetic Disks Coated With Polar and Non-Polar PFPE Lubricants

This paper deals with the measurement of friction force exerted on molecularly thin lubricant film surfaces using a specially arranged pin-on-disk type friction tester. The measurements were carried out by sliding a 1.5-mm-diameter glass ball slider on a rotating disk surface with small loading force. Polar and non-polar PFPE lubricants were dip-coated on magnetic disks covered with diamond-like-carbon (DLC) film. Lubricant film thickness was varied to constitute multiple layered film structures on the DLC surface. To clarify the stratified effect of thin lubricant film on friction, a lightly loading force and a slow rotational speed were selected. The tested results showed that the friction force on non-polar lubricant surfaces increase slightly for mono-layer and multi-layer cases, while the friction force on polar lubricants show steady and gradual increase with increasing loading force. We conclude that friction force at small loading force is dependent intimately on the thickness, molecular weight and end-group functionality.

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

Advances in Tribology ◽

10.1155/2012/923818 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7

Author(s):

H. Tani ◽

Y. Mitsuya ◽

T. Kitagawa ◽

N. Tagawa

Keyword(s):

Surface Roughness ◽

Ion Beam ◽

Lubricant Film ◽

Friction Forces ◽

Magnetic Disks ◽

End Groups ◽

Cluster Ion ◽

Perfluoropolyether Lubricant ◽

Gas Cluster Ion Beam ◽

Pin On Disk

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 N2clusters, with or without Ar cluster-assisted tough carbon deposition prior to N2irradiation, 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.

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S162012 Adhesion and Friction Force Measurement of Ultra-thin Liquid Lubricant on Magnetic Disks by Pin-on-Disk test

The Proceedings of Mechanical Engineering Congress Japan ◽

10.1299/jsmemecj.2012._s162012-1 ◽

2012 ◽

Vol 2012 (0) ◽

pp. _S162012-1-_S162012-4

Author(s):

Hiroshi TANI ◽

Toshiya MITSUTOME ◽

Yusuke TSUJIGUCHI ◽

Masayuki KANDA ◽

Norio TAGAWA

Keyword(s):

Friction Force ◽

Force Measurement ◽

Magnetic Disks ◽

Liquid Lubricant ◽

Pin On Disk ◽

Disk Test

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Reduction of Head Wear on Thin-Film Magnetic Disks

Magnetic Storage Symposium: Frontiers of Magnetic Hard Disk Drive Tribology and Technology ◽

10.1115/2002-trib-0258 ◽

2002 ◽

Cited By ~ 2

Author(s):

Youich Kawakubo ◽

Shunichi Miyazawa ◽

Kenjirou Nagata ◽

Shinichi Kobatake

Keyword(s):

Thin Film ◽

Hard Disk Drives ◽

Hard Disk ◽

Disk Surface ◽

Disk Drives ◽

Magnetic Disks ◽

Surface Flattening ◽

Magnetic Disk ◽

Pin On Disk ◽

Wear Tests

It is necessary to reduce head wear to develop future hard disk drives. For this purpose, we have been studying transparent pin-on-disk wear tests on thin-film magnetic disks. We reported that pin wear on thin-film magnetic disk showed running-in effects. The reason of the running-in was considered to be a result of disk surface flattening. This means that if we could introduce an efficient burnishing technique, we could reduce head wear in operation. We then introduced a burnishing technique using a hemispherical diamond slider and compared pin wear on disk surfaces with and without burnishing. The results showed that the pin wear was reduced by the introduction of the burnishing technique. We consider that burnishing with hard round slider is another way of reducing head wear on future disk surfaces.

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Head Wear in Contact Recording Systems

Magnetic Storage Symposium: Frontiers of Magnetic Hard Disk Drive Tribology and Technology ◽

10.1115/2003-trib-339 ◽

2003 ◽

Author(s):

Youichi Kawakubo ◽

Shinichi Kobatake ◽

Shunichi Miyazawa ◽

Shinichi Nakazawa

Keyword(s):

Thin Film ◽

Wear Debris ◽

Hard Disk Drives ◽

Disk Surface ◽

Disk Drives ◽

Magnetic Disks ◽

Disk Lubricant ◽

Pin On Disk ◽

Contact Recording ◽

Wear Tests

The possibility of disk failure, a common failure mode conventional HDDs, was studied in conditions supposed contact recording systems. For this purpose, transparent pin-on-disk wear tests were performed on thin-film magnetic disks with sliding load less than 5 mN. We found that visible wear scar did not appear on disk surfaces. Wear debris were found be buried on the disk surfaces. This showed that the reduction of head wear and vibration are two main problems to be solve for future hard disk drives. We then studied effects of disk lubricant and tape burnishing of disk surface on pin wear. The results showed the higher the molecular weight of lubricants, the lower the pin wear, and tape burnishing reduced pin wear.

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A Numerical Study on Heat Transfer and Lubricant Depletion on an Anisotropic Multilayer Hard Disk

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.232.770 ◽

2012 ◽

Vol 232 ◽

pp. 770-774

Author(s):

Yan Zeng ◽

Xiao Yang Huang ◽

Wei Dong Zhou ◽

Sheng Kai Yu

Keyword(s):

Heat Transfer ◽

Laser Power ◽

Numerical Study ◽

Disk Surface ◽

Lubricant Film ◽

Multilayer Structures ◽

Lubricant Depletion ◽

Thermal Anisotropy ◽

Anisotropy Effect ◽

Higher Temperature

This paper presents a numerical investigation on the effect of thermal anisotropy of the top layer alloy on heat transfer and lubricant depletion on the disk surface in a heat-assisted magnetic recording (HAMR) system. The disk consists of multilayer structures and a thin layer of lubricant on the top surface. Cases under different laser powers and initial lubricant film thicknesses are examined. The top-layer alloy thermal anisotropy does show non-negligible effect on the heat transfer and lubricant depletion. With the top-layer alloy being more anisotropic, higher temperature increase and lager lubricant depletion can be observed on the disk surface. The results also show that the thermal anisotropy effect is more significant under a lower laser power but nearly keeps no much difference under different initial lubricant film thicknesses. Thus it is of importance to include the thermal anisotropy effect of the top-layer Co-alloy when simulating the heat transfer and lubricant depletion in practical multilayer HMAR systems, especially for the cases under the condition of lower laser power, as the effect cannot be neglected under such conditions.

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Friction-Heating Maps and Their Applications

MRS Bulletin ◽

10.1557/s0883769400055822 ◽

1991 ◽

Vol 16 (10) ◽

pp. 41-48 ◽

Cited By ~ 42

Author(s):

H.S. Kong ◽

M.F. Ashby

Keyword(s):

Normal Force ◽

Frictional Heat ◽

Unified Approach ◽

Magnetic Disks ◽

Heat Flows ◽

Bulk Heating ◽

Friction Heating ◽

Image Position ◽

Pin On Disk ◽

Nominal Contact Area

Friction is often a nuisance, but it can be useful too. Brakes, clutches, and tires rely on it, of course, though the inevitable fractional heat remains a problem. Other applications use frictional heat: friction cutting and welding, skiing, skating, and curling. The damage to magnetic disks caused by head-disk contact and the striking of matches are also examples.This article illustrates a framework where the thermal aspects of friction can be analyzed in an informative way. It uses a unified approach to the calculation of flash and bulk heating, and a helpful diagram—the frictional temperature map—to display the results. The method is approximate, but the approximations have been carefully chosen and calibrated to give precision adequate to most tasks, and the gain in simplicity is great.The symbols used in this article are defined in Table I.When two contacting solids 1 and 2, pressed together by a normal force F, slide at a relative velocity ν and with coefficient of friction ü, heat is generated at the surface where they meet. The heat generated, q, per unit of nominal contact area, An, per second isThe heat flows into the two solids, partitioned between them in a way that depends on their geometry and thermal properties. Figure 1 shows one geometry commonly used for laboratory tests: the pin-on-disk configuration. The pin is identified by the subscript 1, the disk by subscript 2. Solid 1 can have properties which differ from those of solid 2.

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