Study On Tribological Performance Of NiAl Matrix Self-lubricating Composite With Addition Of Graphene

Friction and lubrication must be taken into account due to relative motion.Currently,liquid lubrication is the most widely used method to solve these problems.However,liquid lubricant cannot fulfill the higher requirements with the development of industry because of its inherent defects.As liquid lubrication fails at high speed,heavy load,elevated temperature and other extreme working conditions.Coating technology is an alternative to lubricate in such suffering working conditions,but its application is restricted because of high expense and limited working life.Solid self-lubricating composite materials still show excellent tribological performance in those complicated working conditions.It makes solid self-lubricating composite materials be one of research hotspots in the field of tribology.This study selects NiAl alloy as matrix material,graphene as additive to fabricate NiAl matrix composite with graphene,and investigates its tribological performance under different working conditions.The results indicate that graphene acting as lubricant and reinforcement can help to reduce friction coefficient and wear rate.The tribological performance of NiAl matrix composite with graphene(NMCG)varies with the changing of working condition.Friction coefficient decreases with the increase of load from 2 to 8N,and friction coefficient increases with the increase of load if load is higher than 8N;but wear rates increase with the increase of load from2-12N.The test result shows that wear rate decreases with the increasing of temperature from 100 to 600?,but friction coefficient keeps low till temperature increases to 400?,and then wear rate increases rapidly.Friction coefficient of NMCG decreases when sliding velocity increases from 0.2 to 1.2m/s,while the wear rate decreases with the increase of sliding velocity.The existence of graphene can enhance toughness and improve strength of NMCG,which could reduce the damage caused by stress.The excellent tribological performance of NMCG is attributed to the formation of friction layer on worn surface during sliding friction,and the friction layer consists of lubrication layer on surface and plastic deformation on subsurface.Graphene in NMCG shows the capability of promoting the formation of friction layer.Moreover,this study discusses the formation and effecting mechanisms of friction layer.The formation of friction layer will improve the mechanical property of contact area,reducing the volume loss caused by stress.The results show that formed lubrication layer help to lower friction coefficient.The plastic deformation layer facilitates to resist wear owing to its high elastic,high hardness and high bonding strength with substrate.The researches and discusses of friction layer could enrich the theoretical system of solid self-lubricating materials.