Improvement of Friction Durability of Magnetic Head-Disk Interfaces by Thin Lubricant Films on Diamond-like-carbon Protective Layers
Current Topics and Emerging Issues in Materials Sciences Vol. 1,
20 April 2023
,
Page 62-82
https://doi.org/10.9734/bpi/cteims/v1/18875D
Abstract
Nanowear and viscoelasticity were evaluated to study the nanotribological properties of lubricant films of Z-tetraol, D-4OH, and A20H on diamond-like-carbon protective layers, including their retention and replenishment properties. For A20H and thick Z-tetraol-coated disks, the disk surface partially protrudes, and the phase lag (tan \(\delta\) ) increases with friction. Good replenishment enables the lubricant to reflow and cover areas depleted after sliding contact between the head and disk. The retention and replenishment of lubricants depend on their interactions with the diamond-like carbon (DLC) film on the surface of the disk. This result is consistent with replenishment of the lubricant upon tip sliding. For the D-4OH-coated disk, the tan \(\delta\) value decreases with tip sliding, similar to the case for the unlubricated disk. The durability of the lubricant-coated magnetic disks was then assessed using friction tests with increasing and decreasing loads. Regardless of the load, the unlubricated disk's friction force quickly increases after about 30 reciprocating cycles. By plotting the friction coefficient's relationship with the load and reciprocating cycle number, the lubrication state can be calculated. There are four categories in which the friction coefficient can be placed. In addition, the changes in the friction coefficient were mapped with respect to the lubrication state, emphasizing four distinct areas of lubricant behavior. The lowest friction area constitutes fluid lubrication. The second area constitutes the transition to mixed lubrication. The third area constitutes boundary lubrication. The highest friction of the fourth area results from surface fracture. The boundary lubricating area of the A20H lubricant was wide, because of its good retention and replenishment properties.
- Friction durability
- extremely thin lubricant
- magnetic disk
- fluid lubrication
- boundary lubrication
- perfluoropolyether lubricant