Molecular Dynamics Study Of Frictional Contact Behavior Of Ni/Cu Bilayer Film

The anti-friction and anti-wear properties of the material surface have an important influence on the reliability of the mechanical structure.Nanofilms are now widely used in micromechanical systems,aerospace and biomedical applications.Microstructures are subject to surface frictional wear during ultra-precision machining and use,which reduces the working performance and service life of the parts.Therefore,it is necessary to carry out the research on the surface morphology of microstructure and the frictional contact characteristics of material surface by lubrication of nano-metal coating under different contact conditions,which is helpful to provide reference for the research of enhancing the wear resistance of metal coating.In this paper,based on the study of Ni/Cu bilayers,the effects of factors such as surface texture and material crystallographic orientation on the frictional contact of Ni/Cu bilayers are considered under different contact forms.The effects of crystallographic orientation,texture direction,abrasive grain radius and contact depth on the friction process and substrate deformation of Ni/Cu bilayer films under various motion conditions were investigated by the MD method,in order to provide a reference for the frictional properties and ultra-precision machining of metal films.The main findings of this paper for the study of the frictional contact mechanism of Ni/Cu bilayers are as follows:(1)Under the condition of abrasive scraping action,the average contact force increases with the increase of scraping speed,abrasive grain radius and contact depth.The appropriate increase of nickel film thickness can effectively enhance the Ni/Cu interfacial action and reduce the contact resistance of the substrate to abrasive grains.The 45° lattice angle of the nickel film can effectively reduce the elastic-plastic deformation of the Ni/Cu bilayer film substrate.The study based on the lattice angle concludes that the dislocation distribution and the number of lattice reconstruction atoms of the substrate are less and not significantly different for the five textural features.(2)Under the action of spin-scraping contact of abrasive grains,the average contact force increases with the increase of speed,abrasive grain radius and contact depth,and decreases with the increase of spin speed.The increase in nickel film thickness makes the Ni/Cu interface more effective in resisting dislocation growth and slip.The 45° lattice angle of the nickel film effectively enhances the lubrication effect of the coating of the double-layer film matrix.Based on the findings of the lattice angle study,it is found that the spin-scraping effect results in a more uniform accumulation of atoms and less plastic deformation in substrates with different textural features.(3)Under rolling scraping contact conditions,larger scraping speed,rolling speed,abrasive grain radius and contact depth will make the plastic deformation of the substrate increase.The appropriate increase of nickel film thickness is also beneficial to maintain the structural integrity of the substrate.The dislocation distribution and the number of reconstructed atoms of the substrate at 27° Ni film lattice angle are the least and the structural integrity of the substrate is the best.The effect of the textural features on the substrate is significant under rolling and scraping conditions.Compared with the scraping contact action,the spin-scraping contact can effectively reduce the number of atomic accumulation in front of the abrasive grains,decrease the contact resistance,and further weaken the elastic-plastic deformation of the Ni/Cu bilayer film.Under the contact condition of rolling and scraping,the repeated contact action along the x-axis and z-axis in both positive and negative directions is more likely to make the substrate structure fail.