Exploring low friction of lubricated DLC coatings in no-wear conditions with a new relaxation tribometer

The friction behavior of ta-C and a-C:H as DLC coatings is investigated using a new method. Two green lubricants were used: oleic acid and glycerol. This technique is able to measure with a great accuracy, without any force transducer, two contributions of friction. The first one, μ 0 is the transient friction coefficient at zero speed (which differs from the static and dynamic friction coefficient at constant speed) and the second one, μ 1 is a velocity-dependent friction coefficient. This work aims to investigate the different friction contributions for steel/steel, steel/DLC and DLC/DLC contacts. Moreover, the results are compared with a conventional reciprocating cylinder-on-plane tribometer working at constant sliding speed. Overall, the results show the superiority of the ta-C/ta-C combination in reducing μ 0 .