Durability of magnetic thin-film rigid disks in nitrogen and helium environments

Pin-on-disk experiments were performed using hemispherical pins of manganese zinc ferrite sliding on rigid disks composed of thin films of a sputtered cobalt-nickel-platinum alloy and diamond-like carbon, with perfluoropolyether as the topical lubricant. The durability, as measured by the total distance slid to the point at which the friction coefficient increases rapidly, is poor (40 to 110m) for dry helium and dry nitrogen. The addition of various amounts of water vapor in a nitrogen ambient results in more than two orders of magnitude improvement in durability. The failure mechanism is based on the rate of debris agglomeration in different environments. (from authors' abstract)