a-C:H:Si:O film are generally described as fully amorphous films consisting of two interpenetrating and interbonded networks, one being a silica glass (SiOx) network and the second one an amorphous hydrogenated carbon network (a-C:H). Their friction behaviour has been found to be dependent on the sliding environment and in particular, on the relative humidity. As demonstrated by Scharf et al., humidity plays a major role in the composition and the mechanical behaviour of the interfacial film generated while sliding: in dry environment, a carbon-rich tribofilm with low shear strength is found, while under humid conditions it consists of silica fragments and exhibits a higher shear strength. In this work, we investigated the effect of environment on the tribological performance of a-C:H:Si:O films by using a linear reciprocating pin-on-flat tribometer under controlled environment. Inert gases (N2, Ar, dry air) were successively blown in the contact, leading to a decrease in the friction independently of the gas for non-patterned a-C:H:Si:O. We were thus able to show that while the frictional response strongly depends on the mechanics of the interface, water vapour protects the surface against wear while oxygen promotes it. Furthermore, the effect of surface patterning on environment-dependent tribological performance of a-C:H:Si:O was also investigated. The tribochemical reactions occurring while sliding patterned and non-patterned (as grown) a-C:H:Si:O against a 52100 steel were also studied by different analytical techniques.

Understanding the influence of environment and surface patterning on the tribological behaviour of silicon-oxide containing diamond-like carbon (a-C:H:Si:O) films

253rd National Meeting (2017)

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