Effect of Cr Doping Content on the Mechanical and Tribological Properties of Cr-C/DLC Films on ACM Rubber Surfaces

Recently, diamond-like carbon (DLC) films have been considered for enhancing the wear resistance of rubber because rubber exhibits a high coefficient of friction and is prone to wearing out. However, the significant difference in thermal expansion coefficients between DLC films and rubber often leads to high residual stresses and poor interfacial adhesion, which limits their application in dynamic seals. In this study, Cr-C/DLC composite films were prepared using magnetron sputtering, and the effects of varying Cr contents (0.8 at.%, 1.4 at.%, 4.3 at.%, and 7.0 at.%) on interfacial adhesion and tribological properties were investigated. Scanning electron microscopy (SEM) analysis revealed no distinct demarcation lines in the composite films, indicating strong adhesion to the substrate. X-ray photoelectron spectroscopy (XPS) analysis revealed that chromium doping promoted the conversion of sp3 bonds to sp2 bonds. Adhesion and tribology tests revealed that introducing a Cr-C layer with higher Cr content within the range of 0.8 at.% to 7.0 at.% enhanced the film’s adhesion, reducing the CoF value of the composite film to 0.13–0.14. Specifically, the RF80 sample (4.3 at.% Cr) exhibited excellent interfacial adhesion and optimal tribological performance, with a CoF value reduced to 0.13 and wear rate of 3.1 × 10−4 mm3/(Nm). In summary, modulating the Cr doping content can significantly enhance the interfacial adhesion strength and tribological properties of Cr-C/DLC composite films on rubber surfaces, providing an effective solution for optimizing rubber seals.