Author(s)

C. Scholz, C.-A. Manier & M. Woydt

Abstract

Nowadays, diamond-like carbon (DLC) coatings are mainly used in many low loaded applications such as in machine tools, computer devices and many more. Especially the automotive industry anticipates a benefit in applying such coatings in association with the lightweight construction of mechanical parts, for instance in gear components. The ulterior motive is a global performance increase regarding environmental impact and power efficiency. In recent years, the slip-rolling resistance of DLC, a-C and ta-C thin film coatings was improved considerably. In view of the mechanical application of thin film coatings, there is still room for improvements. It was experimentally shown, that a-C and ta-C coatings can be slip-rolling resistant at room temperature in unaddivated paraffin oil up to ten million cycles under Hertzian contact pressures up to P0max = 2.9 GPa. Typically, the prime coated steel substrates were made of the hardened and tempered steels 100Cr6H and Cronidur 30. The aim of the work this to overtake these results, i.e. at higher maximum Hertzian pressures up to P0max = 4.2 GPa. Under such extreme conditions, it is necessary to choose special steels to avoid the failure of the substrate and to permit a higher load carrying capacity of the coating-substrate-system. In consideration of the increased substrate properties, two high toughness spring steels and an ultra-high toughness aerospace steel were tested on a twin disc tribometer of the Amsler type as well as on an Optimol TwinDisc test rig under mixed/boundary conditions. Different factors such as residual stresses of the substrate, influences of the lubrication, and wear behaviour were investigated. The respective results are presented here. Keywords: slip-rolling, high toughness steel, DLC, a-C, thin film coating.

Keywords

slip-rolling, high toughness steel, DLC, a-C, thin film coating