Effect Of Nano-carbon On The Tribological Properties Of Gcr15 Bearing Steel Under Boundary/Solid Lubrication

Carbon nanomaterials(including graphene,nanodiamond,onion like carbon,etc.)have the characteristics of lower friction,lower cost,and less pollution.They are widely studied.According to the investigation,it is found that different carbon nanomaterials have different mechanisms for reducing friction in oil lubrication;graphene and nanodiamond form a core-shell structure under solid lubrication conditions,which greatly enhances the friction reduction effect.This article is inspired by the lubricity of carbon nanomaterials and the interaction between carbon nanomaterials and S and C elements.By adding different carbon nanomaterials to three different lubrication conditions of MoDTC/MoS_x/DLC,CSM friction and wear tests And RM-1 vacuum friction and wear testing machine were used respectively to conduct friction experiments to explore the tribological properties of carbon nanomaterials under boundary/solid lubrication.Research indicates:(1)Under the boundary lubrication condition of nano-carbon materials on GCr15steel,the friction coefficient of PAO containing MoDTC additive is significantly reduced(the friction coefficient is reduced from 0.16 to 0.05)after adding nano-diamond or onion carbon,The addition of nanomaterials effectively promotes the formation of MoS_x friction film which is due to the carbon,MoS_x friction film ultimately enhances its anti-friction performance and reduces the optimal amount of MoDTC(from 1 wt%to 0.1 wt%);meanwhile,the addition of MoDTC effectively enhances the carbon nanomaterials in PAO The dispersion stability in the oil makes a large amount of sp~3 carbon embedded in the wear scar surface during friction,which greatly improves the anti-wear performance;graphene does not help the anti-friction and anti-wear performance of PAO oil containing MoDTC additives.(2)Under the condition of solid lubrication on MoS_x coating with nano-carbon materials,different carbon nano-materials show different anti-friction effects.In a vacuum environment,the friction coefficient of the spread nano-diamonds is the highest(~0.04),and the spread friction of the graphene is the lowest(~0.018).After being exposed to the atmosphere,the friction coefficient increases,but the law remains unchanged,indicating that sp~2 carbon and MoS_x under solid lubrication The synergy of the coating is the best.(3)Under the condition of solid lubrication on DLC film under nitrogen environment,the coefficient of friction of carbon nanomaterials is~0.02 when the spreading rate of carbon nanomaterials is 5%,and the tribological performance has not been improved because of the running-in period After the consumption of carbon materials.When the spreading rate is about 15%,the friction coefficient will be greatly reduced to 0.008 in a very short time(~700 circle)after adding onion carbon,and it will continue to be maintained after 180 minutes;there is no significant change in adding graphene(~0.02);The friction coefficient of nano-diamond will increase to0.04~0.05 instead.The above results indicate that sp~3 carbon alone is not conducive to the self-lubrication of the DLC film.The ultra-low friction coefficient is the result of the joint action of sp~2 carbon,sp~3 carbon and DLC film.