Effect of graphite on friction and wear characteristics of molybdenum dithiocarbamate

The effects of graphite powder on the friction and wear characteristics of molybdenum dithiocarbamate MoDTC were studied in reciprocated sliding contact using a ball-on-plate type tester. The oil used was squalane, a pure hydrocarbon. The addition of MoDTC alone to the oil showed a high coefficient of friction at an early stage of a rubbing test, since the extent of the formation of a surface film containing MoS2 was insufficient to decrease the coefficient of friction. The high friction at the early stage brought about noticeable wear. On the other hand, the addition of graphite powder together with succinimide-type dispersant to the oil containing MoDTC considerably improved the friction and wear performance not only at the early stage but also at the steady stage. The added graphite powder seems to cover the part of rubbing surfaces without a film containing MoS2 to reduce the friction and wear, not only at the steady stage after the running-in process, but also in the running-in process or at the early stage.