TRIBOLOGY OF DIAMOND-LIKE CARBON-COATED VCR HEAD DRUMS

Friction and wear behaviours between video cassette recorder (VCR) hea d drum and tape were investigated by using a home made tribometer. Fri ction coefficients of uncoated and diamond-like carbon (DLC) coated he ad drums of Al alloy were compared before and after a wear test. Diamo nd-like carbon films were deposited by high frequency plasma enhanced chemical vapour deposition method. The friction coefficients were meas ured in the range of sliding speed from 0.16 to 4.9 m s(-1). The frict ion coefficients of DLC coated head drums have 14% to 30% lower than t hose of the uncoated head drums at low sliding speed (0.16 m s(-1)). A t high sliding speed beyond 3.2 m s(-1), both friction coefficients ha ve similar low values less than 0.1 because air gap is formed between the head drum and the tape. However, the friction coefficients of unco ated head drum significantly increase after the wear test. Furthermore , the friction coefficients become essentially same regardless of the sliding speed. In contrast, those of DLC coated VCR head drums have al most same values as those before the wear test. These contrasting beha viours were discussed in terms of surface damages of uncoated head dru m surface mainly due to the embedded Fe oxide particles which is trans ferred from the test tape. It is further observed that the damage to t he test tape is much reduced when using DLC coated head drums. These r esults show that the DLC coating on a VCR head drum can protect both t he head drum surface and the VCR tape.