Friction characteristics and wear resistance of carbon-coated glass-based rigid magnetic disks

Abstract

Thin film magnetic recording disks each comprising a glass substrate, cobalt-nickel magnetic medium and a carbon overcoat were tested using an environment controlled pin-on-disk type tester. The heads used were thin film heads with a ceramic slider made of 70% aluminum oxide and 30% titanium carbide. It was found that at a load of 100 mN the friction coefficient between the carbon overcoat and the head increased significantly with the sliding distnace travelled, the peak value being in the range 1.4–1.9; when a relatively light load (10 mN) was used, the friction coefficient varied much less. The mechanism of friction build-up was investigated and it was found that carbon debris adhering to the slider rail surfaces was responsible for the increase in friction. With the lighter load, the wear of the carbon overcoat was in the burnishing regime and debris did not form. High speed tests using a pin-on-disk apparatus showed that glass-based thin film disks are more wear resistant than aluminum-based ones, and thin film disks are considerably more wear resistant than oxide disks.