Characterization of nano-wear mechanisms of hard disk coatings

The wear mechanisms of carbon coated computer hard disks with laser-texture d (LT) and mechanically-textured (MT) surfaces were characterized after con tact start/stop (CSS) cyclic tests. Various analytical and mechanical testi ng techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties, and friction characteristics of t he coating and lubricant. These techniques include: the atomic force micros copy (AFM), continuous nano-indentation test, nano-scratch test, time-of-fl ight secondary ion mass spectroscopy (TOF-SIMS), and Auger electron spectro scopy (AES). The CSS test at 15 k cycles resulted in tangible reductions of surface roughness of approximately 3.0 nm and 5.8 nm, respectively, for th e LT bump and MT zone. The elastic modulus and hardness values increased af ter the CSS test, indicating strain hardening of the top coating layer. A c ritical load was identified for adhesion failure between the magnetic layer and the Ni-P layer. The TOF-SIMS analysis also revealed reductions in the intensities of all lubricant elements, indicating wear of the lubricant app lied on the disk surface. All foregoing results confirm the usefulness of t he characterization techniques employed to detect the subtle changes in dis k surface characteristics.