Effect of rubber substrates on the flexibility and tribological properties of diamond-like carbon coatings

In this study, closed-field unbalanced magnetron sputtering was employed to deposit a diamond-like carbon (DLC) film with Cr as the middle layer on three elastomeric substrates, namely nitrile rubber (NBR), fluorine rubber (FKM), and ethylene propylene diene monomer (EPDM) rubber, respectively. In addition, effects of these rubber substrates on the structure and properties of DLC films were investigated. Results revealed that after the bending test, several new cracks are produced on the DLC-coated EPDM rubber and NBR rubber, while debonding is not observed, indicative of the good flexibility and adhesion of DLC films on EPDM rubber and NBR rubber. Furthermore, tribological properties of NBR rubber and EPDM rubber were significantly improved by the DLC film, and almost no film damage was observed on the wear track, while the DLC coated-FKM exhibited severe wear due to the gradual peeling of the coating. Film shedding was caused by the extremely smooth FKM substrate, which led to low film adhesion. Different tribological properties of the coated rubbers were closely related to the difference in surface roughness and mechanical properties of the rubber substrates. • Using unbalanced magnetron sputtering technology to deposit DLC with Cr as a interlayer on NBR, EPDM, FKM • The substrate roughness shows considerable influence on the adhesion. • The friction properties of coated NBR, EPDM and FKM are compared systematically.