Abstract
In this paper, the influence of graphite (Gr) on the dry sliding tribological properties of phenolic resin (PF) composites was studied under different sliding speeds of 3.1–47.1 m/s. The wear mechanism was investigated by the observation of the morphology of the transfer layer during the dry sliding process. It was found that the addition of Gr could decrease the friction coefficient and wear rate effectively, and the friction coefficient and wear rate decreased with the increase of Gr content in the range of 10–30 vol.%. The dominant wear mechanisms of PF-based friction composites changed from adhesive wear to fatigue wear (in the form of peeling-off) in the high sliding speed condition after the addition of Gr. The addition of Gr effectively reduced the sensitivity of PF-based friction materials to sliding speeds, and thus enhanced the stability of the friction coefficient. When the content of Gr was above 20 vol.%, the stability of the friction coefficient was relatively steady.
Highlights
The development of high-speed trains necessitates higher requirements to the brake system
The PF shows high wear rate and a large fluctuating friction coefficient, which should be used coupled with the solid lubricant for stable tribological performances [23,29,30,31]
Cho et al [41] investigated the tribological properties of solid lubricants for automotive brake friction materials
Summary
The development of high-speed trains necessitates higher requirements to the brake system. Cho et al [41] investigated the tribological properties of solid lubricants for automotive brake friction materials. Alajmi et al [42] investigated the correlation between mechanical properties with specific wear rate and the coefficient of friction of Gr-epoxy composites. Recent investigations mainly focus on the influence of surface morphology variation on the tribological properties of resin-based multi-component friction materials under different pressures and sliding speeds. The tribological properties of friction material are directly affected by the formation process and composition of transfer layers generated during the sliding contact. The study aims to identify the effect of Gr on the formation of a lubricating layer of Gr–PF composite in the dry sliding process, revealing the wear mechanisms. After releasing the pressure and taking the specimen out of the mold, they were put into an oven and post-cured at 180 ◦C for 5 h
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