Effect of laser heating on the smear behavior of PFPE lubricant films on magnetic disks in air and helium

Abstract

We investigated the smear characteristics upon laser heating in air and helium. We used magnetic disks coated with the perfluoropolyether (PFPE) lubricant D-4OH. The surface of the rotating disk was heated by laser irradiation using a pin-on-disk tester setup in a sealed chamber. The temperature was varied from 258°C to 540°C. When the lubricant film was heated by the laser, the lubricant evaporated from the surface of the disk by desorption or decomposition and adhered onto a hemispherical glass pin placed 5 μm above the disk surface as smears. The smears on the pin were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). It was found that the amount of smear under exposure to helium gas is greater than that to air at high temperatures. In addition, this interesting result may be attributed not only to the different lubricant depletion mechanisms due to laser heating under the two environmental conditions, but also to the diamond-like carbon (DLC) thin film at a relatively low temperature of approximately 260°C.