| In view of the fact that currently used imidazolium ionic liquids contain toxic elements such as B,P,and S,which are prone to corrosion of metal friction pairs.The1-octyl-3-methylimidazolium lactate ionic liquid(L-L108),which without toxic elements,was used as the lubricant to study its lubricating properties.Around this ionic liquid,the main contents of this article are as follows:The lubrication performance of L-L108 as the pure lubricant under the condition of steel-steel friction pair was studied.The friction and wear experiments were carried out at different rotating speeds and loads.Results indicate that the lowest friction coefficient of 0.023 was achieved when the rotating speed was 200 r/min and the load was 5 N,and the stability of the friction coefficient is good.Compared with the ionic liquids L-P108,L-B108 and SAE 10W-40,which have been used as reference lubricants in the literature,the friction coefficient were reduced by 66.2%,59.6%and 78.5%,respectively,and the effect of antifriction is remarkable.In addition,the friction pair was changed and the friction tests were carried out under the condition of steel-copper and steel-aluminum friction pair.As a result,the L-L108 had better lubrication performance than other lubricants,indicating that the lactate ionic liquid is an excellent solvent that can be used as a lubricant.By observing the wear surface morphology,it is found that L-L108 has less wear under lubrication and a certain regular texture structure is formed on the surface.This structure is conducive to the formation of secondary lubrication in the friction process and it plays an important role in improving the antifriction and antiwear properties of the lubricants.The tribological properties of L-L108 as additives in base oil were investigated.When the SAE 10W-40 was used as the base oil,adding a small amount of ionic liquid can reduce friction and wear resistance.When L-L108 with a mass fraction of 1.0%was added,the friction coefficient was reduced to 0.081,which was 24.3%less than SAE10W-40.Compared with the addition of L-P108 and L-B108 ionic liquids,the addition of L-L108 has the best anti-friction properties.When the PEG was used as the base oil,when the mass fraction of 3.0%L-L108 was added,the friction coefficient reached the lowest,which was 0.055,which was 19.1%lower than that of the PEG lubricating oil,and was better than the other two ionic liquids as the base oil.It can be seen that the lactate ionic liquid is a lubricating oil additive with good lubricating properties.The lactate ionic liquid has excellent antifriction and antiwear properties,on the one hand it can be attributed to the adsorption capacity of ions:negatively charged anions(Lac~—)in liquids can interact with metal friction pairs during friction.The formed positive charge points combine to form a stable anion adsorption layer on the surface of the friction pair,thereby a stable physical adsorption film is formed through the ionic on the surface of the friction pair.The molecular structure of L-L108 contains hydroxyl and double bonds,exhibiting stronger polarity than other imidazole ionic liquids,so the formed physical adsorption film is more firm.On the other hand,it can be attributed to the tribochemical reaction:XPS results suggested that the tribochemical reaction between the lactate ionic liquids and the steel surface occurred to form the tribochemical reaction film during the friction process.Thereby,the lactate ionic liquid exhibits excellent antifriction and wear resistance. |
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