Influence of tribological conditions on the dry friction mechanism of PVD Zr–C:H hard coatings

The ball-on-disk method was used to determine the tribological properties of Zr–C:H films deposited by cathodic arc plasma deposition (CAPD) in low-temperature PVD processes (not exceeding 180 °C) on the 100Cr6 steel substrates. Different matchings with counter-specimen material (100Cr6, Al2O3, Si2N4) and different tribological conditions of a friction, at the same time maintaining the constant power in a friction zone expressed by the product of load and sliding speed, were applied during the tests. It was revealed, that values of a friction coefficient obtained during the tests and a wear rate coefficient of coatings and counter specimens are not only determined by the characteristics of material but also by the characteristics of the whole tribological system and strongly depend on working conditions of a friction test and matched materials. It was also revealed, that especially dangerous effects on durability of carbon coatings occurred when a friction zone carried a heavy load simultaneously with low sliding speed and additionally when carbon coatings were matched with very hard material of a counter specimen (Si3N4). Analysis of elements concentration distributed perpendicularly to the worn groove profile used to determine the mechanism of tribological wear enabled to reveal the occurrence of coating and counter-specimen materials in a friction zone.