To enhance the friction property of Al–Si alloy cylinder liner in running-in period, MoS2 coatings were electrodeposited on the chemical-etched surface of cylinder liner. The friction coefficient decreased by 15% comparing with the original honed surface, indicating the better friction property. This is because the synergistic action between solid lubricant and etched surface. MoS2 coatings prevent the direct contact between silicon particles and piston ring during friction. At top dead center, the oil film was thinnest and even was broken during the reciprocate friction. When oil film was invalidated, MoS2 coatings undertook lubrication. Then, MoS2 coatings were depleted, and advantage of etched surface became apparent.

Purpose: The paper aims to investigate the friction and wear properties of three surface-modified piston rings matched with a chromium-plated cylinder liner. Design/methodology/approach: Samples were taken from the chromium-plated cylinder liner, Cr-Al2O3 ring, CrN ring and Mo ring. Tribo-tests were conducted on a reciprocating sliding tribometer under fully formulated engine oils. Friction coefficients and wear depths of three friction pairs were tested. Surface morphologies of cylinder liners and piston rings before and after test were analyzed. Findings: Experimental results show that in the Cr-Al2O3 piston ring, scuffing occurred easily when matched with the chromium-plated cylinder liner; compared with the Mo ring, the CrN ring could decrease the wear depth of the piston ring from 2.7 to 0.2 μm, and the wear depth of cylinder liner remained; however, the friction coefficient increased from 0.113 to 0.123. The tribological performances of three surface-modified piston rings were significantly different when they matched with chromium-plated cylinder liner. Originality/value: Chromium-plated cylinder liner and the three kinds of surface-modified piston rings have excellent friction and wear properties, respectively. However, according to the systematic characteristics of internal combustion (IC) engine tribology, only the appropriate cylinder liner–piston ring can improve the tribological performance of the IC engine. This paper reports the tribological performance of three surface-modified piston rings matched with a chromium-plated cylinder liner. The results can be used as reference for the design of high-power-density diesel engine.

To enhance the anti-wear property of aluminum–silicon (Al–Si) alloy, three processing technologies—chemical etching, mechanical honing and laser finishing—were compared in terms of their effects on anti-wear performance. The treated Al–Si alloy cylinder liner samples were worn against a piston ring by a reciprocating sliding tribotester; the anti-wear performance was represented by the friction coefficient and wear loss; and the wear mechanism was determined by establishing stress contact models. The results showed that the best time for both the chemical etching and mechanical honing treatments was 2 min, and the optimal laser power was 1000 W for the laser finishing treatment. The three processing technologies could all remove the aluminum layer and make the silicon protrude on the surface to avoid the plastic flow of aluminum during the friction process. The laser finishing could not only protrude the silicon particle but also make its edge rounded and smooth, which decreased the stress concentration. Therefore, the Al–Si alloy cylinder liner treated with laser finishing had the best anti-wear performance.

A starved lubrication experiment and analytical model have been developed to investigate the friction condition transition (FCT) at the interface between a piston ring and a cylinder liner with the piston ring reciprocating liner test rig. To obtain a solution for the friction condition transition, phase space trajectories are used to extract the transient features of the friction force. The trajectories have three typical patterns for starved lubrication conditions. The irregular friction force of different strokes is classified based on the trajectories. When the projection of the trajectories in the phase space enters into the third pattern variation, this indicates the onset and progression of scuffing. The autocorrelation analysis of the wear surface topography at the stroke end validates the characterization method.