Jean M. Dasch

The Role of Hydrogen Atmosphere on the Tribological Behavior of Non-Hydrogenated DLC Coatings against Aluminum

Diamond-like carbon (DLC) coatings are promising candidates as tool coatings for dry machining of aluminum alloys as aluminum has a lower tendency to adhere to the DLC surface when compared to other hard coatings in ambient conditions. This study investigated the tribological behavior of non-hydrogenated DLC coatings against a 319 Al alloy in various environments including ambient air (47% RH), vacuum (6.65 × 10 − 4 Pa), inert gases (Ar, He, and N 2 ) and a mixture of 60% He-40% H 2 . Unlike the results from the other test conditions, significantly low coefficient of friction (COF) values, ranging between 0.01–0.02, were observed in the 60% He-40% H 2 mixture after a brief period with a high COF of 0.70. The formation of a carbonaceous tribolayer on the counterface and the passivation of the sliding surfaces by the chemisorption of hydrogen were suggested as mechanisms that might have been responsible for the very low COF behavior of the non-hydrogenated DLC coatings in the 60% He-40% H 2 mixture.