A study of the tribological behaviour of CrN, Graphit-iC and Dymon-iC coatings under oil lubrication

The use of hard ceramic coatings (e.g., TiN and CrN) in the field of machine components is now widely accepted. The development of low-friction wear-resistant coatings that can run dry or in a minimum amount of oil is becoming increasingly more important. Two recently developed carbon-based coatings (TCL Graphit-iC™ and Dymon-iC) which have already been shown to exhibit very high sliding wear resistance and low friction in dry conditions, were compared to a CrN coating in oil lubricated conditions. In this paper, long-term pin-on-disc tests using a chrome steel counterface ball were carried out on coated HSS test samples. All the coatings performed well with applied contact pressures exceeding 1 GPa, but the TCL Graphit-iC™ and Dymon-iC coatings also exhibited the desirable characteristic of protecting the counterface material. Reasons for this behaviour are discussed.