Effect Of Nano-Diamond On Tribological Properties And Film Formation Of ZDDP

Zinc dialkyl dithiophosphate(ZDDP)is one of the most widely used and most widely used lubricant additives.It forms an anti-wear effect by forming a friction reaction film at the friction interface.However,due to the P,S and other elements will affect the post-processing of harmful pollutants in vehicle engine exhaust,which makes the application of ZDDP in modern engine lubricants challenged.Nano-diamond particles not only have the characteristics of small size of nano-materials,strong adsorption capacity and high reactivity,but also have the advantages of environmental friendliness,high hardness and stable chemical properties.However,the application of nano-diamond particles is affected by many factors,it is difficult to completely replace the use of ZDDP.Therefore,it is meaningful to reduce the amount of ZDDP by studying the synergistic effect of nano-diamond particles on ZDDP.In this study,ZDDP and nanodiamond particles were added to the PAO base oil,the concentration of nanodiamond particles was distinguished by the method of precipitation,and the method of mechanical dispersion was used to exclude the influence of the dispersant.The friction and wear tester and atomic force microscope(AFM)were used to study the tribological properties of different lubricating oil samples at the contact interface of multiple micro-convex bodies and the in-situ film formation under the contact of single micro-convex bodies.Scanning electron microscope,energy spectrometer,Raman spectrometer,atomic force microscope and other characterization methods were used to investigate the effect of different concentrations of nano-diamond particles on ZDDP tribological properties and film formation,and the mechanism of nano-diamond particles was studied.The research results show that:(1)The addition of nano-diamond particles has little effect on the friction performance of lubricating oil containing ZDDP,but it can greatly improve the anti-wear performance of ZDDP.In this study,it was found that the anti-wear performance of lubricating oil after adding nano-diamond particles can be doubled.The mechanism of action of the nano-diamond particles is to produce a grinding effect on the friction interface during the friction process,eliminating local stress concentration,and making the friction reaction film more uniform.(2)The performance of nano-diamond particles is significantly affected by the concentration.Without the addition of dispersants,when the concentration is too large,the friction reaction film of ZDDP will be damaged due to agglomeration and precipitation to increase wear.When the concentration is too low,it also has a slightly adverse effect on the wear performance.(3)The addition of nano-diamond particles will affect the growth rate of the friction reaction film.In the early stage of film formation,the addition of nano-diamond particles can increase the film formation speed of ZDDP by 3-4 times,and the friction reaction film is denser and has better performance,and is more difficult to be removed during the film formation process.