Effects of Environmental Conditions on Tribological Characteristics of Thin-Film Disks

It has been postulated that the higher the lubricant diffusion coefficient, the higher the hard disk drive (HDD) reliability. However, it has been reported that head wear increased in higher temperature environment even though the diffusion coefficient became larger. To understand this contradiction, we studied the effects of environmental conditions on pin wear using a transparent pin-on-disk seek wear test. The results showed large scattering in data points especially in low temperature or low humidity conditions but the reason of the scattering was not clear. Judging from the averaged data, we considered that the higher the temperature or the relative humidity, the lower the pin wear. These results followed our expectation, though the reason for the difference between prior head wear and present pin wear tests were not clear. However, the behavior of lubricant picked up on pin surface was not the same under the two high diffusion coefficient / low wear conditions. In high temperature conditions, lubricant pick-up became large. On the other hand, the amount of picked up lubricant became less in higher humidity environments. We consider more detailed studies are necessary to understand the effects of environmental conditions on head disk interface tribology.