Lubrication studies of head-disk interfaces in a controlled environment: Part 1: Effects of disk texture, lubricant thermal treatment and lubricant additive on the durability of the head-disk interface

Abstract

Decomposition and tribological performance of Z-Dol and X-1P lubricants on the magnetic recording thin-film disks are studied during sliding in a high-vacuum environment. Gaseous products generated from the head±disk interfaces and frictional force are detected and monitored as functions of the sliding distance by using a quadrupole mass spectrometer and friction measurements. The thin-film disks with mechanical and laser texture were used and different thermal treatments were applied to the lubricant films. The effects of the disk texture, lubricant thermal treatment and lubricant additive on the degradation and durability of head±disk interface, are studied in detail. Experimental results show that, firstly, fluorocarbon fragments are generated from lubricants during a period of sliding with a low and stable coefficient of friction, followed by a sharp rise in the frictional force and generation of gaseous products of diamond-like carbon overcoat material. The disk texture has effects on the decomposition of the lubricant and durability of the head±disk interface; the laser-textured disk surface caused Z-Dol lubricant to decompose at lower sliding distances and with more gaseous species compared with the mechanically textured disk. Thermal treatment of the lubricant films and the application of X-1P as an additive to the ZDol lubricant improved the durability of the head±disk interfaces.

Studies on degradation mechanisms of lubricants for magnetic thin-film rigid disks

“…Decomposition of PFPE lubricants begins from the onset of sliding, and the DLC overcoat starts to wear simultaneously from the beginning of the sliding for untreated lubricants but was well protected in the case of chemically bonded lubricants. Similar experimental results were also obtained on laser-textured disks [8,21]. Besides the thermal treatment of the lubricant films for chemical bonding, ultraviolet (UV) irradiation could also be used for the chemical bonding of PFPE lubricant films on a hard disk surface.…”

“…The tribotester features a mass spectrometer with its ionization chamber located in the line of sight of the slider-disk interface so that emission from the interface can be monitored in situ during the sliding under high vacuum. A detailed description and an overall schematic diagram of this apparatus can be found in references [8] and [25].…”

“…The density of bumps was 900 mm ¡2 . The map of the laser-textured disk surface measured using an atomic force microscope can be found in reference [8].…”

“…The data in Table 4 show that catalytic reactions depend on both the type of catalyst and the reaction temperature. When in contact with Al 2 O 3 powder at 200 8C, 1 per cent weight loss of Z-Dol lubricant needs about 0.8 hs; 1 per cent weight loss of YR lubricant needs more than 6 h. However, when the temperature decreases to 25 8C, 1 per cent weight loss of Z-Dol lubricant needs 13 h, and 1 per cent weight loss of YR lubricant needs more than 40 h. In sliding test conditions, the lubricants begin to degrade at the very beginning of the sliding; the lubricants on the sliding tracks were completely degraded in a very short time (1 or 2 min); by then the DLC coating and substrate were worn out [8,21]. However, it can be clearly seen from Table 4 that the catalytic reactions need much more time than several minutes even for only 1 per cent weight loss of the lubricants.…”

“…Recent studies have found that PFPE lubricants may easily degrade in high humidity. The head-disk interface fails very quickly in high humidity probably because of the hydrolysis of Z-Dol (the commercial name for the PFPE lubricant from Ausimont USA Inc.) and the competitive adsorption on the slider surface of water molecules with Z-Dol lubricant molecules [6][7][8]. Like every other lubricant, PFPE lubricants decompose when subjected to high temperatures.…”