Friction and wear studies of magnetic thin-film rigid disks with glass-ceramic, glass and aluminum-magnesium substrates

Glass-ceramic and glass substrates are beginning to be used in the construction of magnetic thin-film rigid disks for their rigidity, shock (dent) resistance, and smoothness over commonly used Ni-P coated aluminum-magnesium substrates, Coefficients of static friction (stiction) and kinetic friction in clean ambient (class 100) and durability in various environments were measured for disks constructed from two types of glass-ceramic substrates and for the substrates themselves and for glass disks. For comparison purposes, the same tests were also conducted for commercially available aluminum-magnesium (Al-Mg) disks. The results show that, although stiction differences can exist between different types of lubricated finished glass-ceramic disks, differences between lubricated substrates and corresponding unlubricated, finished disks are minor. The wear performance of lubricated glass-ceramic disks with low stiction is also clearly better than that of lubricated glass-ceramic disks with high stiction and is comparable to that of lubricated glass and Al-Mg disks. The wear performance for all carbon-coated disks tested is the best in nitrogen or argon environments, the worst in vacuum, and intermediate in humid or oxygen environments. For the glass disks coated with silicon dioxide, the presence of water vapor in the operating environment improved its wear performance. Adhesion forces due to meniscus formation at the head-disk interface, which cause high stiction, were calculated for all lubricated disks and substrates. The trends of the calculated values agree with that of the experimental results for coefficients of static friction.