Friction properties of DLC/DLC contacts in base oil

Diamond-like carbon (DLC) coatings are promising surface coatings in terms of friction and wear performance and are beginning to be introduced in internal combustion engines, mainly because of the need to reduce friction and because of compositional constraints on engine lubricants. This paper compares the friction and wear behaviour of twelve different types of DLC coating lubricated with an API Group III base oil. A clear dependence of friction and wear on DLC type has been observed. ta-C coatings provide lower boundary friction than the other types. W-DLC coatings experience more wear whereas Si-DLC and a-C:H coatings show very little wear.