Tribological properties of carbon nitride overcoat for thin-film magnetic rigid disks

For the purpose of developing a new protective overcoat through the understanding of friction and wear mechanism at nanoscale, two types of commercial carbon coatings and CNx coatings, deposited by ion beam assisted deposition (IBAD) on magnetic media (1.8 '' magnetic rigid disk) were tested against Si3N4 using pin-on-disk test equipment. Wear surfaces were analyzed with AFM to measure the wear rate of the disks. It was observed that wear and friction of both carbon- and carbon nitride-coated disks was localized in the surface texture (bumps). A method of calculation of wear volume and wear rate for this case has been proposed. Wear rate of the carbon nitride-coated disk was found to be about 10-times lower than that of the disk coated with commercial carbon (90%C-10%Si) of the same thickness. Carbon nitride coating also provided about 3-30-times longer life than commercial carbon coatings. The friction coefficient observed for the CNx coating was lower than that of carbon coatings observed at the same load.