Investigation of tribological properties of MoS2 and graphite coatings under different environmental conditions

In this study, 10 mm in diameter and 20 mm length made of AISI1008 steel samples coated with graphite and MoS2 powders which widely used today as a solid lubricant with lead-spinning method. A pin-disc type tribometer was designed and manufactured for wear and friction tests. The experiments were carried out under three different environment; dry, oily and oil + 5% Molykote-A added. In dry environment, MoS2 and graphite coatings were found to reduce friction by an average of 42% and 51%, respectively. The friction coefficients for MoS2 and graphite coatings in oily medium, were respectively about 10 times and 8 times lower than those in dry environment. In investigation of abrasioned surfaces, it was seen that scratch marks and locally metal regions on abrasioned surfaces which had worn in dry environment. In case of oily environmental, the coatings were superficially worn and no metal region was seen on abrasioned surfaces. For 30%, 60% and 95% reliability values, the lifetime values of MoS2 and graphite coatings were statistically calculated.