• • DLC topcoat reduces MCD surface roughness from 155.33 nm to 123.77 nm and UNCD roughness from 92.43 nm to 81.90 nm, directly lowering asperity contact and interfacial shear stress in seawater—critical for minimizing seal leakage and wear in rotary equipment.
• • MCD/DLC composite achieves a 32.08% reduction in steady-state friction coefficient and a 12.22% reduction in specific wear rate compared to monolithic MCD, extending seal ring service intervals and reducing maintenance costs in marine propulsion systems.
• • UNCD/DLC composite delivers a 26.67% friction coefficient reduction and a 20.92% wear rate reduction versus monolithic UNCD, with the finer grain structure providing a smoother foundation that enhances DLC lubrication efficiency under boundary conditions.
• • DLC incorporation accelerates the sp2 phase transformation and graphitization at the sliding interface, as confirmed by Raman and XPS, reducing debris generation and counterface ball damage—mitigating abrasive wear and prolonging the lifespan of mating components in seawater environments.