Effect of bonded lubricant films on the tribological performance of magnetic thin-film rigid disks

Abstract

Polar perfluoropolyether lubricants are widely used for topical lubrication of thin-film rigid disks. However, little is known about the role of bonded lubricant on tribological performance. In this study, as-applied lubricant films, after thermal treatment and after thermal treatment and washing to remove unbonded fraction, have been studied. The bonded fraction of lubricant films on coated disks made with AlMg and glass substrates was measured at various applied lubricant thicknesses, soaking times and thermal treatments, with silicon wafer as a reference. Friction and wear performance of lubricated disks against Al 2O 3TiC microsliders was measured. Results show that bonded lubricants thickness increases initially with increasing soaking time, baking temperature and baking time, and then levels off. Bonded lubricant thickness also increases initially with increasing applied lubricant thickness and levels off above a certain film thickness. A critical lubricant thickness exists above which coefficients of static and kinetic friction increase rapidly and durability decreases rapidly, and this thickness increases with disk roughness. A rise in static and kinetic friction above a critical value of film thickness is associated with meniscus forces. The drop in the disk durability above a critical level may result from the observed stick/slip phenomena and erratic friction at lubricant thicknesses which is thick as compared to disk surface roughness. It is further noted that lubricant film with mobile and immobile fractions is important for the disk to have a long life.