Sliding-speed effects on self-lubricating marine composites: A comparative assessment of tribological, mechanical, and thermal performance

Net-zero by 2050 demands scalable renewables. Ocean wave/tidal energy, though denser than solar and wind, remains at low TRL. A pivotal barrier is the material durability and performance of ocean (hydraulic) rod linear bearings that remain key components of WECs including point absorbers. This study presents a comparative mechanical, thermal, and tribological evaluation of eight commercial and newly developed self-lubricating bearing materials, including thermoplastics, thermosets, elastomers, and a bronze-based alloy, under unlubricated conditions. The materials incorporate diverse reinforcement architectures, including short fibers, woven and continuous fiber fabrics, and solid lubricant particulate fillers. Tribological testing was conducted under an 18 hrs long-duration dry reciprocating pin-on-flat configuration at 0.02–0.1 m/s under 250 N load. Friction behavior, wear rates, and surface degradation were recorded. Post-test analyses using SEM, FTIR, and 3D surface profilometry revealed distinct wear mechanisms and transfer film behavior. Wear maps integrating friction, wear rate, and a normalized multi-parameter performance index reveal sliding-speed-dependent tribological transitions and enable ranking of marine composites. The findings establish a foundational understanding for bearing failure mechanisms, predictive design and material selection in ocean tribological systems.