Tribological behaviour of diamond-like carbon films used in automotive application : a comparison

International audienceExcellent tribological behaviour such as high wear resistance and very low friction coefficient make diamond-like carbon (DLC) very interesting for automotive applications in order to reduce friction losses in engines. In this work, mechanical properties, structure and tribological behaviour of two DLC films (DLC-A and B) designed for automotive applications are compared. Better hardness and Young modulus of one of the coating are investigated by Raman analysis. Two laboratory tribometers with and without lubrication are used to evaluate the tribological behaviour of both coatings. In each test, a running-in period is clearly identified. Most of the wear takes place during this period which also presents a higher friction coefficient. Even if the structure of both DLC films remains stable in depth during the test, the DLC-B has the best wear resistance for both lubricated and unlubricated conditions. Later on, this best wear resistance of DLC-B is validated by measurement on test rig