Frictional Behavior of C60 Microparticle-Coated Steel

ABSTRACTThe frictional behaviors of 304 stainless steel disks coated with C60 microparticles, both containing benzene and free of benzene, have been studied under different loads and sliding speeds with a pin-on-disk configuration in ambient air atmosphere at room temperature. The results indicated that the coating containing benzene, benzene-solvated C60 microparticles (C60·4C6H6), reduced friction as well as wear. The coated samples showed a 50–70% reduction in friction coefficient in comparison to uncoated samples. Neither the coated nor the uncoated sample showed significant change in friction coefficient for different sliding speeds. Under different loads, the uncoated sample had almost the same friction coefficient. However, with the increase of load, the friction coefficient of C60·4C6H6-coated disk showed a minimum value of 0.25 at 25 g load and then reached the uncoated values beyond 50 g load. The coefficient of friction of the disk coated with benzene-free C60 showed a slight increase with load, reaching the value of uncoated 304 stainless steel disk at about 40 g. The reduced friction of the solvated-C60 coated 304 stainless steel is probably due to the lowered shear strength of the hcp structure of C60·4C6H6 molecular crystal in which the benzene molecules are intercalated. The results of this study suggest the importance of the presence of second component, in addition to C60, in the coating materials in order for them to form a preferred crystal structure with low shear strength as far as using C60 as a solid lubricant is concerned.