MoSx coatings were prepared by bipolar-pulse DC unbalanced magnetron-sputtering system with the variation of coating thickness at different Ar pressures. The composition and surface morphology were determined by using energy dispersive X-ray and scanning electron microscopy; the structural characterisation was analyzed by X-ray diffraction. The friction and wear properties were investigated by fretting tests in air with less than 10% and 50% relative humidity. At 0.40 Pa pressure, (002) basal plane orientation was formed throughout the coatings. At 0.88 Pa and 1.60 Pa pressures, (002) basal plane orientation was only noticed in the first stage of coating growth (around 0.20祄 in thickness), and then edge orientations with their basal planes perpendicular to the surface would be evolved in the coatings. Humidity has a minor influence on the coatings that have (002) basal plane orientation, whereas the tribological properties of MoSx coatings with edge orientations are greatly affected by humidity. The mec MoSx coatings were prepared by bipolar-pulse DC unbalanced magnetron-sputtering system with the variation of coating thickness at different Ar pressure. The composition and surface morphology were determined by using energy dispersive X-ray and scanning electron microscopy; the structural characterization was was analyzed by X-ray diffraction. The friction and wear properties were investigated by fretting tests in air with less than 10% and 50% relative humidity. At 0.40 Pa pressure, (002) basal plane orientation was formed throughout the coatings. At 0.88 Pa and 1.60 Pa pressures, (002) basal plane orientation was only noticed in the first stage of coating growth (around 0.20 祄 in thickness), and then edge orientations with their basal planes perpendicular to the surface would be evolved in the coatings. Humidity has a minor influence on the coatings that have (002) basal plane orientation, and the tribological properties of MoSx coatings with edge orientations are greatly affected by humidity. The mec