Macroscale superlubricity enabled by the synergy effect of oil and S–C co infiltration coating on 20CrMnTi steel surface

To explore the macroscopic superlubricity in industrial field, S-C co infiltration treatment refers to the sulfurization on the carburized gear steel to achieve a synergy lubrication effect. It was found that the carburized layer at the bottom provides high-strength support. And the surface sulfurized layer with pores immersed oil shows good solid-liquid synergistic lubrication to realize stable superlubricity under the load of 0~800 N. Although it lost the stable superlubricity after increasing the load to 1200 N, the tribological coefficient and wear depth were reduced by 72.9% and 19.4% respectively compared with the original surface. This research proposes a novel oil-solid synergistic superlubricity system, which exhibits significant potential for practical applications.