| The electromagnetic gun is an important weapon of the future.During the actual firing of the electromagnetic gun,the rail will generate huge resistance heat and friction heat due to the high current and ultra-high speed,thus reducing the life of the rail.The purpose of this paper is to prepare a conductive lubricating coating for aluminum armatures to reduce the frictional and resistive heat generated during the current-carrying friction process.Using the excellent lubricity and electrical conductivity of graphene and metallic tin,a tin-graphene composite coating was prepared on a 6061 aluminum alloy substrate using a nanoparticle composite electrobrushing method.The surface and cross-sectional morphology of graphene flakes,composite coating,and the morphology of abrasion marks after dry and current-carrying friction were characterized and analyzed by Raman spectroscopy(Raman),atomic force microscopy(AFM),X-ray diffractometer(XRD),and scanning electron microscopy(SEM).Finally,the frictional and resistive heat generated by the armature/guide parsimonious model within 1 ms was simulated by ANSYS Workbench finite element.The results show that the graphene in the prepared nanoparticle brushing solution is uniformly dispersed,and the graphene in the composite coating can play the role of grain refinement,effectively reducing the cavities and cracks in the coating and making the coating flatter and denser.the Sn-GE composite coating exhibits good wear reduction and lubrication performance under both dry and 1 A current-carrying friction conditions.Among them,Sn-0.5GE showed the best performance under both dry friction and 1 A current-carrying friction conditions,reducing the average coefficient of friction by 80.7% and 69.3%,respectively,and the volume wear by 92.3%and 67.78% compared to the aluminum substrate,and the composite coating did not show electrical erosion under low current conditions.Under dry friction conditions,the graphene will adhere to the grinding ball or press into the cracks to reduce frictional wear.Under low current conditions,the graphene will "lie flat" on the surface of the wear marks due to the electric field force and turn into amorphous graphite or three-dimensional graphite microcrystals to protect the substrate from further wear under the electric-force coupling.The prepared Sn-0.5GE armature coating can effectively reduce the mechanical frictional heat generated by sliding at1 ms,and has less effect on the generation of resistive heat,while the Sn-0.5GE armature coating has melted within 1ms to form a liquid lubricating film that can further improve the armature/rail contact,thus not generating arc heat.It was found that the Sn-GE material system can reduce electrical erosion during the current-carrying friction process and reduce the phenomenon of "sticky aluminum" in the wear substrate.Due to the limitations of the experimental conditions,high-current current-carrying friction and live-fire experiments were not conducted,but it can still provide a reference material system for the preparation of armature coatings for electromagnetic guns. |
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