Friction, wear, and interfacial chemistry in thin-film magnetic rigid disk files

We present results of a study of hemispherical pins of manganese-zinc ferrite sliding against rigid disks composed of thin films of a sputtered cobalt-nickel-platinum alloy and carbon, with perfluoropolyether as the topical lubricant. The contact life, as marked by the total distance slid to the point at which the coefficient of friction increases rapidly over the steady state value, is much longer in air with 50 percent relative humidity than in dry air or vacuum. The wear debris generated in humid air is much finer and is enriched with cobalt on its surface. In dry air and vacuum, the debris is substantially larger than one micron and tends to be enriched with nickel on its surface. We present a hypothesis which explains the wear mechanisms in various operating environments.