| Pin-on-disk sliding tests of PFPE lubricated, amorphous carbon overcoated magnetic thin-film hard disks have been performed using a controlled environment tribochamber. The tribological behavior of this system has been studied under different environmental conditions including vacuum, dry gases (He, N{dollar}sb2{dollar} and air), and gases with varying moisture content (N{dollar}sb2{dollar} and air). Durability and friction are found to be strongly dependent on the ambient environment, and are sensitive to water vapor and oxygen content. Various surface analytical techniques both in situ and ex situ are used to correlate friction and wear behavior to surface chemical effects at the sliding interface.; Results from durability testing in nitrogen environments ranging from very dry to 80% RH indicate an extreme dependence on humidity, with contact life increasing two orders of magnitude at humidities of less than 1%. Oxygen present in an air environment improves the durability over that of dry inert gases and vacuum, but there is little improvement with the addition of water vapor and the friction coefficient rises steadily throughout the test. These results are explained by competitive wear processes: suppression of agglomeration of wear particles in the presence of moisture mitigates the amount of damage caused by wear debris, while accelerated wear of the carbon overcoat during sliding in air acts to reduce the durability in humid conditions.; In additional investigations of the ceramic/hard disk interface, comparisons of Mn-Zn ferrite pins sliding against unlubricated and PFPE lubricated disks indicated that the lubricant improved contact durability, but was less effective in humid air environments than humid nitrogen environments. While the carbon overcoat is shown to remain macroscopically intact during sliding, scanning tunneling microscopy (STM) of disk surfaces shows roughness changes during initial stages of sliding wear. |
