Tribochemical reactions of very thin layers on magnetic recording disks

Abstract

Surface reactions of thin oil layers on magnetic recording disks have been studied during sliding with an Mn-Zn ferrite slider under high vacuum conditions. Gaseous products, fluorinated carbons, CO 2 and H 2 were detected with a quadrupole mass spectrometer, even at a low load of 9.8 × 10 −2 N. Surface analysis by X-ray photoelectron spectroscopy with a small spot size revealed that metal fluorides were formed on the wear track. This is good evidence for the tribochemical reaction of fluorinated oils with the disk surface. There was marked gas formation after 4300 repeated sliding cycles and, at the same time, the coefficient of friction increased from 0.3 to 0.6. It is concluded that thin layers of perfluorinated oil were removed from the disk surface through chemical means during sliding. It is found that the disappearance of the oil layer was accelerated by the tribochemical reaction and that the carbon layer acted as a protective layer for the reaction of oil. Fresh metal surfaces formed by friction with a slider play an important role in the reaction.