Dealloying-induced surface porosity for enhancing tribological properties of Ag-DLC films under starved lubrication

Abstract Surface porous architectures serving as micro-oil reservoirs offer a promising adaptive self-lubrication strategy for critical engine components under starved lubrication conditions, especially during frequent start-stop cycles. However, the controlled fabrication of such structures on DLC surfaces and their tribological behavior under representative oil-starved conditions remain insufficiently explored. Herein, we propose a novel strategy that exploits the inherent thermodynamic incompatibility and self-migration behavior of Ag in the carbon matrix as a natural advantage. A simple dealloying method was employed to construct surface porous structure on Ag-DLC films via the selective removal of Ag particles, aiming to improve tribological properties under starved lubrication. Results reveal that the size and density of porous structure is regulated by the Ag target current during deposition. Notably, the introduced porous structure significantly mitigates abnormal wear at the friction interface while maintaining a low and stable friction coefficient under starved lubrication. The porous structure acts as micro-oil reservoirs, and it effectively replenishes the boundary lubricating film via load/thermal stimuli induced oil release. Mechanisms attribute to the synergistic effects of replenished the boundary lubricating film, reduced real contact area, and graphitized transfer films. These findings provide a foundation for designing intelligent adaptive DLC-based lubrication systems capable of autonomous oil replenishment under intermittent lubrication regimes.