Research On The Tribological Properties Of Three BN-based Nanoparticles As Lubricating Oil Additives

Oil lubrication is the key technology to improve the surface friction state,reduce the energy consumption and prolong the service life of equipments.The nature of lubricating oil additives is the main factor to determine the lubrication effect.Nano lubricating additives have better anti-friction and anti-wear properties due to their characteristics of micro-size and high surface energy.Therefore,the research on the friction and wear performance of different nano additives has significant guiding significance for improving the lubricating performance of lubricating oil.In this paper,the tribological properties of two kinds of mixed nano additives(BN/AlN and BN/TiN)and one kind of composite nano additive(BN@C)under different test parameters were carried out by using MRS-10 A four-ball friction and wear tester.Through the analyses of friction coefficient,wear scar diameter,wear morphology,element distribution and valence state,etc,the anti-friction and anti-wear mechanism and self-repair process of nano additives were described.The main conclusions of this paper are as follows:(1)Among the five dispersants,oleic acid,span 80,silane coupling agent KH-550,polyethylene glycol 200 and stearic acid,oleic acid had the best dispersing effect on BN,TiN and AlN nanoparticles.(2)The lubrication performance of BN/AlN and BN/TiN nano additives decreased first and then increased with the increase in mass ratio,and the lubrication performance was the best when the mass ratio was 1:1.With the increase in the concentration of nano additives,the lubrication performance first increased and then weakened.When the concentration of nano BN/AlN was 0.2wt%,the lubrication performance of lubricating oil was the best,and the maximum non-sticking bite load was increased by 38.30%;compared to the pure base oil.When the concentration of nano BN/TiN was 0.6wt%,the lubrication performance of lubricating oil was the best.Compared with pure base oil,and the maximum non-sticking bite load was increased by 65.96%.(3)When the concentration of BN@C was 0.2wt%,the friction coefficient was the lowest,which was 19.28% lower than that of pure base oil.When the concentration was0.4wt%,the wear scar diameter was the lowest,which was 22.34% lower than that of pure base oil.After 5 days standing,the friction coefficient and wear scar diameter of nano BN@C lubricating oil increased by 13.59% and 10.96% respectively,and the friction coefficient and wear scar diameter of nano BN@C lubricating oil increased by 7.57% and5.01% respectively.(4)In the process of lubrication,nano additive particles(BN/AlN,BN/TiN,BN@C)can enter into the friction pair to separate the friction surfaces and change the friction form into rolling sliding mixed friction.The interlaminar slip of nano BN aprticles occurred under the sliding extrusion of upper and lower friction surfaces.At the same time,the carbon materials coated on the BN played a lubricating role,so as to reduce the friction and wear.Nano TiN and AlN acted as micro bearings to reduce friction and wear.Nano particles could be adsorbed and precipitated in the pits on the friction surfaces to repair the matrix wear.The nano BN and TiN reacted with the matrix material to form a new repair film to protect the friction surface.