| Lubricant oil is referred to as the blood of industry,lubrication technology is the most effective wear-resistant and antifriction alternative for mechanical system,and the increasing consumption of lubricant oil industry would necessarily call for the enhancement of lubricant performance as well as the research and development of a new lubricant additive.The nano material-based wear-resistant,antifriction and online self-repairing technology of lubricant oil system for additive modifiers has become one of the development orientations of friction and lubrication technologies,as well as one of the innovative cutting-edge researches of tribology,suggesting great theoretical significance and extensive application prospect.Compared with a single-phase material,the nano-particles lubrication component with two or more different properties shows a higher performance advantage,which can be attributed to better tribological performance of composite particles,as a result of the synergistic effect of different materials and the complementary mechanism of advantageous performances.In this study,through the numerical simulation of wear-resistant molecular dynamics,it simulates the wear mass of soft/hard-phase composite nano-particles lubrication system at the boundary lubrication to predict that its wear-resistant capacity can be significantly enhanced.On this basis,it selects the rare earth borate with catalytic activity and the soft metal In nano-particles as lubricant additive,and performs a lot of long frictional wear comparative tests using various common friction auxiliary material specimens to obtain the optimized technical formula.In addition,it uses the advanced testing method to characterize the morphology of nano-particles and friction test samples,make an analysis of the bonding energy between deposited film and substrate of the friction test sample,and conclude that deposited film and substrate are connected with chemical bonds,which further explains the wear-resistant compensation mechanism of self-repairing film.The present study centers on the wear-resistant antifriction performance of nanometer lanthanum borate and soft metal nanometer In on various metal friction pairs.It mainly covers:1.Optimized process for preparation of nanometer lanthanum borateThe optimized process parameters for preparation of nanometer lanthanum borate are obtained by orthogonal experiment,and TEM morphological characterization and XRD composition assay are performed on its products.2.Preparation of nanometer La2[B4O5?OH?4]3/In composite powder and oil-soluble surface modification? By comparing the preparation and modification of several kinds of La2[B4O5?OH?4]3 /In,the present study selects the on-step preparation-modification of optimized in-situ sol-gel method,and obtain the process parameters.? It configures the sample of La2[B4O5?OH?4]3/In-base oil lubrication system,and characterizes the particle size of composite nano-particles,dispersion and stability of this system.3.It performs and compares the tribological performance tests on La2[B4O5?OH?4]3/In-base oil lubrication system,and makes a mechanism analysis of the test results to obtain the optimized composite ratio and the optimized addition.? It determines the wear-resistant antifriction performance and makes the mechanism analysis of the lubrication system of La2[B4O5?OH?4]3/In composite nano-particles in 45 steel-HT200 and 45 steel-ZCu Zn16Si4 copper friction pair at different composite ratios and in different contents.? It tests the friction and wear performance,WSD and friction coefficient of various oil samples on four-ball apparatus,tests and analyzes the oil film strength PB,and the sintering resistance PD.4.It makes the fracture surface characterization of the composite nanometer La2[B4O5?OH?4]3/In characteristic element on friction surface deposited film and performs XPS analysis of the bonding energy between deposited film and substrate.It also predicts the tribological test results by simulating the wearing of composite particles on steel-copper friction pair using molecular dynamics.Major findings:1.The spherical zero-dimensional La2[B4O5?OH?4]3 nano-particles with an average particle size of 45 nm can be obtained by regulating PH value of the reaction system;2.La2[B4O5?OH?4]3 /In composite nano-particle is prepared using sol in-situ synthesis and one-step oil-soluble modificationThe nanometer In is completely enclosed by amorphous hydrated La2[B4O5?OH?4]3,in core-shell structure,the composition segregation is significantly improved;its average particle size is 60 nm,the largest particle is less than 100nm;the dispersion system that is formed with base oil shows high dispersion and long-term stability,which can meet the requirements of lubricant oil additive and support long-term storage.3.The addition of La2[B4O5?OH?4]3 /In nanometer composite particles would significantly improve the tribological properties of base oil? Under the test condition with a load of 200 N,a linear velocity of 0.5m/s and at the room temperature?30??,on the 45# steel-HT200 friction pair,the lubrication system with single hydrated nanometer La2[B4O5?OH?4]3 particle addition of 2wt% can obtain the optimized comprehensive tribological performance,in contrast with base oil,the average friction coefficient of this lubrication system reduces by 34.6%,and total wear mass of the friction specimen reduces by 70.4%.? The composite nanometer La2[B4O5?OH?4]3 /In can further enhance the wearresistant antifriction self-repairing performance of lubricant oil,when the composite ratio is 3:7 with an addition of 2wt%,the configured composite nano-powder lubrication system makes the average friction coefficient of 45#steel-HT200 friction pair reduced by 52.6% if compared with base oil,the wear mass of friction specimen is negative,suggesting the hard repairing with “negative wear”.Under the same test conditions,on the 45# steel-HT200 friction pair,the optimized parameters of composite ratio and addition of La2[B4O5?OH?4]3 /In composite nanoparticles are consistent with that of 45#steel-HT200 friction pair oil sample system.In such a case,the copper specimen has the least wear mass?0.32mg?,the lowest friction coefficient?0.029?,92.4% and 59.2% lower than base oil respectively.? For La2[B4O5?OH?4]3/ In composite nano-particles operating on the point contact higher pair,the optimal process parameters for La2[B4O5?OH?4]3 and In are the mass ratio of 7: 3 and the addition of 3%,in such a case,compared with the pure base oil lubrication system,WSD,friction coefficient of composite nanometer lubrication system reduces by 71.6% and 33.8%,respectively;the maximum non-seizure load PB,sintering load PD increases by 36.5% and 50%,respectively.3.The research on lubricant tribological mechanism of La2[B4O5?OH?4]3/ In composite nano-particles demonstrates that under boundary lubrication conditions,La2[B4O5?OH?4]3 /In composite nano-particles lubrication system forms the composite lubricant film involving Fe B,La2O3,B2O3 and single In on the friction surface through mechanical friction chemical reaction,in which the lubricant film is a self-repairing layer mainly composed of chemical or chemical bonds.4.Numerical simulation results of molecular dynamics show that the new lubricant additive composited by such hard and soft nano-particles has better wear-resistant capability in fluid lubrication model,the variation of the model copper thin wall wear mass is basically consistent with the wear test data curve of copper specimen on the 45#steel-silicon brass friction pair,and the model can be qualitatively used as the reference to prior experiment decision.Main characteristics and innovations of this research:1.The present study firstly attempts to apply La2[B4O5?OH?4]3/In composite nanopowder to the lubricant oil system,and the satisfactory tribological performance is obtained.This research content is innovative with remarkable exploring feature.2.In the preparation of nanometer La2[B4O5?OH?4]3 hydrated lanthanum borate,the small-scale but centrally distributed zero-dimensional spherical nano-particles are obtained by regulating PH value of the system,and this process is simple and reliable.3.The preparation of La2[B4O5?OH?4]3 /In composite nano-particles in core-shell structure using the new sol-gel in-situ method has been developed,and such nano-particle proves superb dispersion and stability.4.Through this study,it is found that the lubrication system constructed by La2[B4O5?OH?4]3/In composite nano-powders not only forms the deposited compensation film layer with its characteristic elements under the long-time surface contact condition with relatively low pressure,but also forms the complete deposited film layer on point-contact steel ball friction surface within a short time,thereby obtaining superb friction and performance,higher oil film strength and sintering resistance.5.Based on the theory of molecular dynamics and numerical analysis,this study constructs the predictive model of the impact of hard/soft composite nano-particles on wear mass of friction pair specimen in lubricant fluid,and this model can be qualitatively used as the reference to prior experiment decision. |
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