TRIBOLOGICAL PERFORMANCE OF THIN-FILM AMORPHOUS-CARBON OVERCOATS FOR MAGNETIC RECORDING RIGID DISKS IN VARIOUS ENVIRONMENTS

An ultrahigh vacuum tribotester equipped with Auger electron analyzer and mass spectrometer is used to study the friction and wear behavior of amorphous carbon coated magnetic thin film rigid disks. The tests include continuous sliding of Al2O3-TiC sliders against lubricated and unlubricated polished and textured disks. Operating environment is found to play an important role in the tribological performance of the carbon overcoat. Wear lives were longest in dry nitrogen and argon environments as compared with ambient environment (with oxygen and water vapor), in agreement with some of the previously reported results. The wear lives of the carbon coatings in vacuum were inferior to those in other environments. In comparison, surface roughness and lubrication play a less significant role in friction and wear for the disks tested. Based on this study, we conclude that poor wear life in vacuum results from intimate slider-to-disk contact. The long life in dry Ar and nitrogen as compared with Ar + O-2 and ambient environment, results from the absence of tribochemical oxidation prevalent in the oxidizing environment.