Bin Zhang

Solid-lubricant coatings for reusable aerospace mechanisms must combine low friction with resistance to material loss during exposure to ambient air. Multi-anion transition-metal dichalcogenide（TMD） films provide a route to tune the growth and load-bearing response of layered solid lubricants without introducing a non-lubricious second phase.Multi-anion MoSxSeyTe2-x-y films were prepared by high-power impulse magnetron sputtering (HiPIMS) at discharge voltages of 600, 650 and 700 V to examine the relationships between growth structure, mechanical properties and ambient tribological performance. The films had similar, nearly stoichiometric chalcogen-to-Mo ratios and compositions within the ideal medium-entropy range of the anion sublattice. X-ray diffraction indicated expanded basal spacings relative to conventional MoS2, while broadened diffraction and Raman features were consistent with structural disorder. Increasing discharge voltage was accompanied by greater surface roughness and lower hardness and elastic modulus, whereas friction varied non-monotonically. At 10 N, V-700 exhibited the lowest mean friction coefficient of 0.039, whereas V-600 achieved the lowest specific wear rate of 3.67 × 10-8 mm3 N-1 m-1. The higher-friction V-650 wear track showed increased fractions of oxidized Mo and Te after sliding, suggesting a contribution from surface chemical evolution beyond the initial mechanical and topographic differences. V-700 additionally completed 20 km of sliding without frictional failure. Discharge voltage simultaneously modified deposition rate, surface roughness and growth morphology; the individual contributions of these coupled changes could not be fully decoupled in the present experimental design.

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.