Rubber is widely used as a crucial sealing material in the aerospace, petrochemical, and automotive industries to prevent contaminants from entering enclosures and lubricants from leaking. However, severe wear and friction occur during sliding motion, which are major causes of seal failure and significantly impact the safety and service life of equipment. To increase the wear resistance of rubber surfaces, diamond-like carbon (DLC) coatings have been extensively studied because of their low friction coefficient, high hardness, excellent wear resistance, and chemical inertness. The hardness, elasticity, and adhesion of the coating can be effectively controlled by adjusting the deposition parameters. This allows the film to accommodate the deformation of the soft rubber substrate, preventing delamination while avoiding thermal degradation or damage to the rubber. Additionally, the chemical composition of carbon-based films, which primarily consist of carbon and hydrogen, is compatible with rubber, ensuring strong interfacial adhesion. In this paper, research progress on the tribological properties of carbon-based films for rubber surface modification over the past two decades is reviewed. In contrast to previous reviews that focused primarily on the general applications and fundamental properties of DLC coatings, this work delves into the distinctive advantages of DLC coatings on rubber surfaces under various deposition conditions. This work explores the underlying mechanisms for friction reduction and wear resistance enhancement while also identifying critical research gaps and proposing future directions for the field.

Ti-based carbon coatings are promising for low-friction and wear-resistant applications, but their performance on steel substrates is often limited by poor adhesion, high residual stress, and unstable tribological behavior under ambient conditions. In this work, TiC_x coatings were deposited on GCr15 bearing steel using a hybrid strategy combining magnetic filtered cathodic arc ion sputtering and magnetron sputtering. Dense Cr/CrN/CrTiN/TiCN graded interlayers ensured strong adhesion and a smooth mechanical transition to the substrate, while the TiC_x top layer was tuned via the carbon target DC current. The TiC_x-1 coating, deposited at 4 A, exhibits an exceptional hardness of 43 GPa and a low friction coefficient of ⁓0.18, demonstrating a superior combination of elastic-plastic properties and wear resistance. Structural analyses reveal that increasing DC current promotes sp² carbon formation and graphitization, while Ti incorporation facilitates TiC reinforcement and the in-situ generation of TiO₂ during sliding. Tribological tests, Raman and FIB-HRTEM observations confirm that friction and wear are dominated by the formation of a stable graphitized transfer film supported by TiO₂, which reduces shear stress and stabilizes the sliding interface. However, excessive carbon enrichment at higher currents destabilizes the transfer film and degrades mechanical integrity, leading to higher friction and wear. These results highlight the synergistic roles of interfacial architecture, carbon bonding evolution, and Ti-assisted tribochemistry in governing the tribological performance of TiC_x coatings. This study provides a novel design strategy and fundamental insights for developing superhard, low-friction coatings for steel components under ambient conditions.

Diamond-like carbon (DLC) films directly deposited on rubber substrate is undoubtedly one optimal option to improve the tribological properties due to its ultralow friction, high-hardness as well as good chemical compatibility with rubber. Investigating the relationship between film structure and tribological performance is vital for protecting rubber. In this study it was demonstrated that the etching effect induced by hydrogen incorporation played positive roles in reducing surface roughness of DLC films. In addition, the water contact angle (CA) of DLC-coated nitrile butadiene rubber (NBR) was sensitive to the surface energy and sp² carbon clustering of DLC films. Most importantly, the optimum tribological performance was obtained at the 29 at% H-containing DLC film coated on NBR, which mainly depended on the following key factors: (1) the DLC film with appropriate roughness matched the counterpart surface; (2) the contact area and surface energy controlled interface adhesive force; (3) the microstructure of DLC films impacted load-bearing capacity; and (4) the generation of graphitic phase acted as a solid lubricant. This understanding may draw inspiration for the fabrication of DLC films on rubber to achieve low friction coefficient.

Diamond-like carbon (DLC) films are deposited on rubber surfaces to protect the rubber components, and surface pretreatment of the rubber substrates prior to the film deposition can improve the adhesion between the DLC films and the rubber. Thus, the principal purpose of this work concentrates on determining the effects of argon (Ar), oxygen (O₂), nitrogen (N₂), and hydrogen (H₂) plasma pretreatments on the adhesion and friction performance of the DLC films deposited on rubber (DLC/rubber). The results indicated that the Ar plasma pretreatment promoted the formation of a compact layer on the rubber surface. By contrast, massive fillers were exposed on the rubber surface after oxygen or nitrogen plasma pretreatments. Moreover, the typical micrometer-scale patches divided by random cracks were observed on the surface of DLC/rubber, except for the sample pretreated with oxygen plasma. The adhesion of DLC/rubber was found to strengthen with the removal of weak boundary layers and the generation of free radicals on the rubber surface after plasma pretreatment. The tribo-tests revealed that DLC/rubber with O₂, N₂, and H₂ plasma pretreatments cannot achieve optimal friction performance. Significantly, DLC/rubber with Ar plasma pretreatment exhibited a low and stable friction coefficient of 0.19 and superior wear resistance, which was correlated to the high adhesion, good load-bearing of the rubber surface, and the approximate sine function of the surface profile of the DLC film.