It has been known that molybdenum disulfide exists as a monophase in the S/Mo composition ratio range from about 1.94 to 2.25. In this study, sputtered molybdenum disulfide films having S/Mo ratio from 1.96 to 2.25 have been prepared on surface of JIS SUS440C rollers for cross roller bearings by applying the positive voltages ranging from 0 to 60 V to rollers. Friction coefficient and wear life of molybdenum disulfide films have been investigated by friction test conducted in air atmosphere of 10 % relative humidity. It is found that better lubricating performance which means longer wear life and lower friction coefficient was obtained in the films having S/Mo ratio from 2.06 to 2.15 near the center of the S/Mo composition ratio range of molybdenum disulfide. On the other hand, sudden drop of lubricating performance were appeared near both limit values of the composition ratio range.
