Study On The Friction And Wear Properties Of Ag,B Doped ZrN Based Thin Films In Basic Lubricants

The improvement of piston friction reduction and wear resistance is of great significance for the efficiency and lifespan of engines.The existing solutions for using additives in basic lubricating oils have serious environmental pollution issues,greatly limiting the application of lubricating oils for reducing friction and wear of mechanical parts.This paper innovatively studied the friction and wear properties of nanocomposite nitride films in basic lubricating oils.By doping active nanometallic particles in the films through physical vapor deposition,environmentally friendly green anti friction and anti wear effects were obtained.In this study,a series of ZrN Ag,ZrBN,ZrBN Ag films were prepared on the basis of ZrN films doped with nano metal particles Ag and nano particle B.The effects of Ag and B addition on the microstructure,mechanical properties and friction and wear properties of the film were studied.The research results are as follows:（1）Research on ZrN-Ag thin films with different Ag contents:The film is composed of fcc-ZrN（111）,fcc-ZrN（200）,fcc-ZrN（220）,and fcc-ZrN（222）phases as a whole.The addition of Ag in ZrN-Ag thin films has the effect of refining grains,with the preferred orientation being fcc-ZrN（111）.With the increase of Ag,the grain size decreases.The hardness of the film increases first and then decreases with the addition of Ag.When Ag increases to 2.17 at.%,the hardness of the film is the highest,at 27.8Gpa.The average friction coefficient of the ZrN-Ag composite film under the base lubricating oil decreases with the increase of Ag content.When Ag content is 16.30 at.%,the average friction coefficient is the lowest,at 0.0815.The wear rate first decreases and then increases as the Ag content increases.When the Ag content is 2.17 at.%,the wear rate is the lowest at 2.551×10^-9mm³N^-1mm^-1.At the same time,research has found that the addition of Ag catalyzes the formation of graphitized carbon like carbon based lubricating films by the carbon chains in the lubricating oil during the friction process of the film,which is likely the reason for the ultra-low friction coefficient and wear rate.（2）Research on ZrBN thin films with different B contents:When the B content reaches7.53 at.%,ZrB₂phase appears,generating amorphous phase BN,and the diffraction peak of ZrN undergoes a significant shift.When the content of B increases to 4.21 at.%,the maximum hardness reaches 27.4Gpa,while when the content of B increases to 7.53 at.%or above,the hardness decreases,resulting in poor mechanical properties.The room temperature friction coefficient of the film with the addition of B gradually decreases,and the wear rate gradually increases.The minimum wear rate is obtained at a B content of 4.21at.%,which is 5.886×10^-7mm³N^-1mm^-1。In lubricating oil friction,the addition of B ultimately stabilizes the friction coefficient at around 0.115,and the wear first decreases and then increases.When the B content increases to 4.21 at.%,the wear rate is the smallest,at1.605×10^-9mm³N^-1mm^-1.Comparing room temperature friction with lubricating oil friction,the generation of oxides during room temperature friction will have an impact on friction,while the production of oxides is less likely to occur during lubricating oil friction and will not have an impact on friction.Adding B element can effectively improve the oxidation resistance of the film.（3）Research on ZrBN-Ag thin films with different Ag contents:The addition of Ag leads to a decrease in the relative content of Zr,When the Ag content gradually increases to over 7.08 at.%,and most of the N in the film exists in the form of BN.The addition of a small amount of Ag improved the mechanical properties of the film.When the Ag content was 1.69 at.%,the hardness reached its maximum value of 29.5Gpa.The content of Ag continues to increase,and the hardness continuously decreases.Thanks to the lubrication effect of Ag,the dry friction coefficient at room temperature shows a monotonic decreasing trend with the increase of Ag content,and the average friction coefficient continuously decreases.When the Ag content is 10.63 at.%,the friction coefficient of the film reaches the lowest,0.442.The wear rate first decreases and then increases with the Ag content.When the Ag content is 1.69 at.%,the wear rate is the lowest at 5.9876×10^-7mm³N^-1mm^-1.In lubricating oil friction,the friction coefficient of Ag addition tends to stabilize,around 0.085,and the wear first decreases and then increases.When the Ag content is 1.69 at.%,the wear rate is the lowest,reaching 1.375×10^-9mm³N^-1mm^-1.Ag can catalyze the formation of a carbon based lubricating film in the lubricating oil,thereby improving the friction and wear performance of the film in the base lubricating oil.When the Ag content is 1.69 at.%,the ZrBN-Ag film still maintains good high-temperature oxidation resistance.