A novel drag test for observing lubricant redistribution due to head-disk interactions

The redistribution of a thin perfluoropolyether lubricant film on magnetic rigid disks after sliding was studied by mapping the surface reflectivity under polarized light using an optical surface analyzer. Both lubricated and nonlubricated regions were created on the disks with a special dip-coating process, and a drag test was conducted with the head placed in the smooth data zone. Due to sliding, a portion of the lubricant film in the initially lubricated regions was displaced into the nonlubricated regions. A numerical procedure was developed to determine lubricant thickness profiles from the surface reflectivity data calibrated by FTIR. The displaced lubricant volume increases with increasing sliding time, increasing initial lubricant thickness, or decreasing sliding speed. Local removal of a lubricant film was observed after long-term parking of the head, and surface diffusion was examined for the diminishing displaced lubricant band.