Graphite crystals consist of a layered structure with stacked graphene sheets, and exhibit self-lubricating properties due to the facile sliding of graphene layers in the horizontal direction, facilitated by weak Van der Waals bonds along the c-axis. When this graphite material is impregnated with a lubricating liquid, it forms a solid and stable lubricating layer, and effectively reduces damage to the counter material from friction-induced wear under conditions of high-load reciprocating motion. This study investigates how oxidation-induced pore expansion and the silane treatment of graphite affect lubricating oil impregnation behavior, the friction coefficient of impregnated graphite, frictional stability, and microstructural changes at the friction surface. It was found that graphite oxidation within the chemical reaction temperature range enhanced porosity and increased the rate of lubricating oil impregnation. The functionalization of the graphite surface with hydrophobic silane coupling agents also significantly enhanced oil uptake, with a pronounced observed improvement when utilizing hydrophobic oils. Under a vertical load of 360 kgf and a surface pressure of 3 MPa, the graphite surface treated with hydrophobic silane and impregnated with oil exhibited the lowest average friction coefficient of 0.192 over 600 cycles. During the friction and wear process, a lubricating layer formed on the graphite surface, which contributes to stable wear performance. This surface modification strategy offers high applicability in industries such as automotive, aerospace, and heavy machinery, with the potential to significantly enhance component performance and extend service life under high-load, low-speed reciprocating conditions.

Enhancing the frictional performance of lubricant oil-impregnated graphite via oxidation-induced pore expansion and hydrophobic silane treatment
    Abstract
    1 Introduction
    2 Experimental
        2.1 Sample preparation
        2.2 Analysis methods
    3 Results and discussion
        3.1 Pore volume control
        3.2 Surface treatment
        3.3 Friction wear behavior
    4 Conclusion
    Acknowledgements 
    References

• Da Hyun Yu(R&D Innovation Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea)
• So Jung Baek(R&D Innovation Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea)
• Kwang Youn Cho(R&D Innovation Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea)
• So Youn Mun(R&D Innovation Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea, School of Chemical Engineering, Pusan National University, Busan 46241, Republic of Korea) Corresponding author
• Jinuk Hwang(R&D Innovation Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea, Graduate School of Convergence Science, Pusan National University, Busan 46241, Republic of Korea)
• Dho Hyun Um(Research Division, SGO Co., Ltd., Incheon 21695, Republic of Korea)
• Dong Gi Seong(School of Chemical Engineering, Pusan National University, Busan 46241, Republic of Korea, Department of Polymer Science and Engineering, Pusan National University, Busan 46241, Republic of Korea)