Among diamond-like carbon (DLC) coatings, hydrogenated amorphous carbon (aC: H) films
are of special interest, since some of them may exhibit coefficient of friction in the millirange,
known as “superlow friction”. This paper will review some key requirements for achieving
this specific friction regime. At first, the formation of a carbonaceous transfer film on the steel
counterface seems necessary for friction reduction. Oxide layers apparently slow down this
build-up, as aC: H surface reacts preferentially with metallic iron. Secondly, the formation …