Ultraviolet or atomic irradiation effect on the polyimide composite lubricating coating

The molybdenum sulfide/lanthanum fluoride/polyimide (MoS2/LaF3/PI) coating was synthesized and irradiated by ultraviolet (UV) or atomic oxygen (AO). The friction and wear behavior were evaluated sliding against GCr15 steel balls (ASTM A295:1998) using a ball-on-disk tribology test rig. This paper aims to discuss these issues. The chemical structure of the irradiated surface was examined by Fourier transform infrared (FTIR) spectroscopy. The worn morphologies of the coatings and counterpart were observed by scanning electron microscopy (SEM) to reveal the wear mechanism. Experimental results indicated that the height and position of the characteristic functional groups and the coefficient of friction of the PI coating changed and the wear rate value decreased after UV or AO irradiation. The effect of LaF3 combined with MoS2 on the tribological properties of the coating and wear mechanism under different irradiated conditions is discussed.