(CANCELED) Modification of rubber surface with hydrogenated diamond-like carbon thin films
Y.T. Pei, X.L. Bui, J.Th.M. De Hosson
University of Groningen, NL
Keywords: DLC thin film, magnetron sputtering, rubber substrate, flexibility, tribology, finite element simulation
Abstract:Thin films of hydrogenated diamond-like carbon (DLC) have been deposited on hydrogenated nitrile butadiene rubber (HNBR) for reduction of friction and enhancement of wear resistance of dynamic rubber seals, by sputtering graphite targets in C2H2/Ar plasma. Coating rubber is very challenging because the film/coating must be flexible and strongly adhered to the rubber surface. The wax removal and pre-deposition plasma treatment are proved to be crucial and effective for the improvement of film performance due to enhanced adhesion. The columnar structure and the crack network formed during deposition enhance the flexibility of DLC thin films and exhibit strain tolerance up to 5%. Under 50% stretch strain and after unloading from the strained status, thin DLC films of ~300 nm thickness still adhere very well on the rubber substrates and no spallation or delamination has been observed. Finite element modeling of stretch test exhibits a good agreement with the experimental results and provides a way for the estimate of interfacial adhesion of the DLC films on HNBR substrates. The thin DLC film on plasma treated rubber exhibits very low coefficient of friction of 0.15 (compared to > 1 of uncoated HNBR rubber). After tribotests even under high normal load of 3 N, almost no damage can be seen on the films. Such tribological property is even better than that of 1µm thick DLC or Me-DLC coated rubbers.