Evaluation of silicon-modified DLC coatings in a dry sliding contact against aluminum EN AW-5083

Diamond-like carbon (DLC) coatings are known to reduce friction and wear. In a dry contact with steel the tribological behavior can be further optimized by adding a certain concentration of silicon to the amorphous hydrogenated carbon coatings structure (a-C:H:Si). However, in a dry contact with aluminum the tribological performance of a-C:H:Si coatings and the optimal silicon concentration is still unknown. In order to define an optimum regarding the silicon concentration, a-C:H:Si-coatings with different silicon contents were deposited on 1.2379 tool material by plasma assisted chemical vapor deposition (PACVD) technology. Tribometer tests were used to analyze the friction and adhesive wear behavior against EN AW 5083 aluminum. Additional, strip drawing were conducted tests to investigate the efficiency of the different silicon contents with a higher proximity to industrial processes. The tests showed a deteriorating friction behavior of the a-C:H:Si coatings with an increase of the silicon concentration. Superposing wear mechanisms between the silicon and the aluminum were determined by a subsequent investigation of the wear tracks as an explanation for the tribological behavior.