Study Of Hydrodynamic Lubrication Performance By Using Ionic Liquids As Additives

Since ionic liquids(ILs) were firstly reported in the field of tribology in 2001, the investigation of them as novel lubricants has been just unfolding. The results show that IL lubricants have excellent tribological properties.Now, many people research friction and wear properties of the ionic liquid by measuring the friction force and analyzing grinding surface.However, the study of hydrodynamic lubrication performance ionic liquids as additives is less. The lubrication film thickness is an important indicator to measuring hydrodynamic pressure lubrication performance. This dissertation is focused on the effects of ionic liquids additives on hydrodynamic lubrication performance, hydrodynamic lubrication film thickness is measured directly in principle of multi-beam interference, including experiment and analyses.The main research content and results include:(1) From boundary lubrication to hydrodynamic lubrication, hydrodynamic lubrication film thickness under different entrainment speeds and loads are measured directly in principle of multi-beam interference by a custom-made test apparatus, polar PEG(polyethylene glycol 400) as base oil with as lubricant additives in situ preparing ionic liquid(IL), the effects of ionic liquid additive on hydrodynamic lubrication properties are studied. The results show that: the ionic liquid lubricants under fluid hydrodynamic lubrication exhibit excellent lubricating properties, it is attributed to the occurrence of the interfacical effect, and the result of XPS analysis proved this conclusion; ionic liquid concentration and the types of anions and cations have some influnence on lubricant film thickness.(2) First the friction coefficients are measured in UMT, then hydrodynamic lubrication film thickness under different entrainment speeds and loads is measured directly in principle of multi-beam interference by a custom-made test apparatus, nonpolar PAO(PAO4 and PAO8) as base oil with ionic liquid(IL) as lubricant additives, evaluated the lubrication properties of ionic liquid additive under hydrodynamic lubrication. The results show that: the ionic liquid lubricants as nonpolar base oil additives under fluid hydrodynamic lubrication exhibit excellent lubricating properties, due to the antion and cation interaction with PAO molecular occurring the interfacical effect; ionic liquid concentration and the types of anions have some influnence on lubricant film thickness. The SEM micrographs of worn surfaces shows that ionic liquid additive reduced friction and wear.(3) The friction coefficients and hydrodynamic lubrication film thickness under different entrainment speeds and loads are measured directly in UMT and principle of multi-beam interference by a custom-made test apparatus, lubricating grease(lithium-based grease) as base grease with metal salts(LiTFSI) and ionic liquid(IL) as lubricant additives, the effects of ionic liquid additive on hydrodynamic lubrication properties are studied. The results show that: the ionic liquid lubricants as lubricating grease additives under fluid hydrodynamic lubrication exhibit excellent lubricating properties and friction-reducing and anti-wear properties, because of the good compatibility of grease and long chain structure and larger polar of ILs occuring the interfacical effect on slider surface; ionic liquid concentration have some influnence on lubricant film thickness, and ILs additive improved the bearing capacity of grease. The SEM micrographs of worn surfaces shows that ionic liquid additive reduced friction and wear.