| With the rapid development of industry,there is a growing demand for high-performance lubricants,and additives are the key functional materials that determine the ultimate performance of lubricants.Sulphur-free phosphorus organic molybdenum is an indispensable additive in internal combustion engine oils because of its friction-reducing and anti-corrosion properties.Sulphur-free organic molybdenum can reduce frictional wear on engine components and improve engine fuel economy by creating a lubricant film containing molybdenum trioxide（Mo O3）through a chemical reaction on the surface of the friction substrate.Especially when compounded with（Zinc dialkyl dithiophosphate）ZDDP,it can form in situ molybdenum disulfide（Mo S2）friction chemical reaction film with excellent friction reduction performance on the friction surface,which can achieve synergistic friction reduction and anti-wear effect without increasing S and P content.However,sulphur-free phosphorus organic molybdenum has problems such as poor oil solubility,extreme pressure performance and anti-wear properties that need to be improved.It is important to design and develop oil-soluble sulphur-free phosphorus organic molybdenum additives with excellent friction reduction and anti-wear properties.As an emerging green lubricant,ionic liquids（ILs）have attracted a great deal of attention in tribology because of their designable molecular structure and good compatibility.Ionic liquid has excellent extreme pressure performance and excellent antifriction and antiwear performance compared with traditional lubricants due to its strong adsorption and thermal stability.Based on the above background,this thesis designed and synthesized an oil-soluble sulfur-free phosphorus organic molybdenum ionic liquid N,N-Bis（2-hydroxyethyl molybdate）-N-methyl-1-hexadecylammonium oleate（Y-Mo）,and systematically investigated its Tribological performance and extreme pressure performance as an additive in alkylated naphthalene（AN30）base oil;explored the synergistic friction reduction and anti-wear performance of Y-Mo and ZDDP in AN30 base oil The friction mechanism of Y-Mo and ZDDP as lubricating additives was investigated by analyzing the composition and structure of friction film,combined with the results of adsorption experiments of the additive package on the friction surface.Finally,the effect of Y-Mo as an additive on the tribological and oxidation resistance properties of commercially available CK-4 10W-30 finished diesel engine oil was investigated.The main research contents and results are as follows:（1）Preparation of Y-Mo and its tribological properties in AN30 base oilAn oil-soluble,sulphur-free organic molybdenum ionic liquid Y-Mo was designed and synthesised by hydrothermal synthesis and ion exchange.The tribological test results show that Y-Mo has good dispersion and tribological properties in AN30 base oil.When it is added at0.3%,the lubricity performance is optimal.the average friction coefficient is reduced by 47%and the wear rate is reduced by 94%compared to the base oil.At the same time,the addition of Y-Mo can improve the extreme pressure performance of the base oil and improve the oxidation resistance of the base oil,and the extreme pressure performance and oxidation resistance can be improved with the increase of Y-Mo addition.The analysis of the structural composition of the friction film shows that when Y-Mo is used as an additive in the base oil,a friction chemical reaction film containing Mo O3 is formed on the surface of the friction substrate,which can effectively improve and repair the frictional wear of the friction substrate,thus showing excellent extreme pressure performance and friction reduction and anti-wear performance.（2）Tribological performance study of Y-Mo and ZDDP additive packages in base oilsThe compounding of Y-Mo with ZDDP effectively improves the high friction and severe wear of the base oil while,at the same time,exhibiting excellent extreme pressure performance and excellent oxidation resistance.Lubricants with the compounded additives showed a 57%reduction in average coefficient of friction and 93%reduction in average wear rate compared to AN30 base oil.The adsorption test results show that Y-Mo can quickly form a multilayer adsorption film of approximately 68 nm thickness on the metal surface,and when Y-Mo and ZDDP co-exist,they possess a viscoelastic film with greater adsorption than Y-Mo,which can better isolate the contact between metals and achieve lubrication effect.Combining the results of friction and adsorption experiments,it is concluded that the combination of Y-Mo and ZDDP has a unique"adsorption-reaction-film formation"lubrication mechanism.especially the composite lubricant at room temperature in the wear surface quickly adsorbed to form an adsorption film of about 166 nm,and then through the friction chemical reaction,the formation of a friction reaction film containing Mo S2,Mo O3,Fe PO4,and other components of the friction reaction film.Among them,metal phosphate and molybdenum trioxide form the anti-wear matrix,while Mo S2 enhances the friction reduction performance,so that the composite friction film effectively reduces the frictional wear of the friction substrate,thus playing a synergistic friction reduction and anti-wear effect.（3）Study on tribological properties of Y-Mo as additive in CK-4 10W-30The tribological performance of Y-Mo and competitor Mo-E in the finished oil was investigated using the SRV friction and wear tester.The results showed that Y-Mo showed excellent tribological performance in CK-4 10W-30,exhibiting superior friction reduction performance than competitor Mo-E,improving the friction reduction performance of the finished oil by 24%and anti-wear performance by 41%,and further improving the oxidation resistance and extreme pressure performance of the finished oil without increasing corrosion.Y-Mo as a finished oil additive shows good friction reduction and anti-wear performance at different temperatures,and as the temperature increases,the friction coefficient tends to decrease gradually,showing excellent high temperature friction reduction performance,which is due to the accelerated friction chemical reaction between Y-Mo and S elements in the finished oil under high temperature conditions,forming a stable chemical reaction film on the wear surface,thus showing excellent friction reduction performance. |
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