Friction and wear studies of various head materials and magnetic tapes in a linear mode accelerated test using a new nano-scratch wear measurement technique

Abstract

A new wear measurement technique was developed to measure the wear of various head materials sliding against different magnetic tapes in a linear mode. A nano-scratch array was produced in the center of the head sample surface using a commercial nano indenter. Using an atomic force microscope, scratch depths were measured before and after running against magnetic tapes as a direct measure of wear on the head surface. Co-γ-Fe 2O 3, CrO 2, metal particle (MP), barium ferrite (BaFe), and metal-evaporated (ME) magnetic tapes were tested against Mn-Zn ferrite. Abrasivity of CrO 2 was much higher than the other tapes. ME tape exhibited no measurable head wear, however adherent transfer debris was observed on the head surface. Mechanisms of head wear for the particulate tapes were dominated by abrasion, whereas with ME tape it was adhesive. Real area of contact measurements were made to determine any changes in the contact of the worn tape surfaces. Generally, the number of contacts increased with wear, however the contact size remained roughly the same. Single layer, double layer, and uncalendered single layer MP tapes were also run against Mn-Zn ferrite to compare differences in friction and wear characteristics. The uncalendered tape was three orders of magnitude more abrasive than the calendered tape. Wear rates of single layer and double layer MP tapes were comparable. In all tests significant edge wear was observed. The severity of the edge grooving (relative to the overall depth of wear) seemed to be inversely related to the stiffness of the magnetic tape. To study the effect of head material on head wear, CaTiO 3, A1 20 3TiC, and SiC head materials were also tested against CrO 2 tape. The relative wear rates of the various head materials were inversely related to their hardness. Finally, tests were conducted with high wear-rate candidate materials, a machinable ceramic and an amorphous glass. These materials could be used in accelerated tests to screen relative tape abrasivities. Both the amorphous glass and machinable ceramic exhibited wear rates about an order of magnitude greater than ferrite.