Friction and Wear Properties of Graphene Lubricating Additive Prepared with Liquid Plasma
MA Qingyi1,SHEN Yan1,YUAN Xiaoshuai2,LIU Zhixiang1,XING Chuanfei1,XU Jiujun1
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(1.Key Laboratory of ShipMachinery Maintenance and Manufacture,Dalian Maritime University,Dalian 116026,China;2.China North Engine Research Institute(Tianjin),Tianjin 300400,China)
Graphene has the unique lamellar structure and slip property and can hence be added to lubricants as a solid lubricating additive to improve the lubrication performance, which meets the demand of high-performance lubricant for the continuously-strengthened diesel engine. About 1 nm graphene flakes were prepared by the liquid plasma method and added to RP-4652D lubricant with 0.05% mass fraction by ultrasonic oscillating dispersion method. The effects of temperature on the friction and wear properties of graphene lubricating additives were studied by the reciprocating test rig of piston ring and cylinder liner. The results showed that the friction coefficient of lubricant decreased by 10.8%, 6.1% and 8.8% respectively and the wear depth of cylinder liner reduced by 14.0%, 7.9% and 6.0% respectively at 150 ℃, 180 ℃ and 210 ℃ after adding the grapheme. The honing topography of cylinder liners for both lubricants was gradually worn with the increase of temperature, but the worn honing pattern of graphene lubricant was better maintained than that of the non-graphene lubricant. For the non-graphene lubricant, the tribo-chemical reactants such as S, P and Zn elements were remained in the worn honing platform and groove. For the graphene lubricant, tribo-chemical reactants were basically absent in the honing groove. It could be attributed to the fact that the soft lamellar graphene acted as a solid lubricant to fill the honing pattern after being brought to the worn surface. In addition, the slip property of lamellar material reduced the consumption of tribochemical reactive film on the worn cylinder liner.
