Study On Current-carrying Friction Behavior Of Cold-sprayed Copper-based Ti₃AlC₂ Composite Coatings

With the rapid development of industrial technology,copper material has been widely used in aerospace,transportation,electronic devices,biomedicine,and other national defense and civil fields.However,the poor wear resistance of copper material is facing great challenges in electromechanical applications.The friction and wear characteristics of the contact surface are directly related to the reliability and durability of the entire electrical contact system.It is of great significance to develop more novel coating materials and improve surface modification technology to prepare conductive and wear-resistant coatings with improved surface properties for improving current-carrying friction failure.In this paper,aiming at the difficulty of co-improving the surface wear resistance and conductivity of current-carrying friction components,the high conductivity metal Cu and conductive ceramic Ti₃Al C₂were innovatively combined,and the Cu-based composite powders with high content of Ti₃Al C₂were designed and prepared.Three kinds of structurally complete Cu-Ti₃Al C₂conductive and wear-resistant composite coatings were obtained by using different process parameters.The micromorphology of the composite coating was observed by scanning electron microscope,the phase composition of the coating was analyzed by X-ray diffractometer,and the mechanical properties of the coating,such as microhardness and bonding strength,were tested by micro-Vickers hardness tester and tensile testing machine,the influence of different spraying temperatures on the mechanical properties of the composite coating was explored,and the electrical properties of the composite coating were measured.The correlation between the coating structure and properties is also analyzed.Finally,the dry friction and wear properties of the coating and current-carrying friction and wear properties are evaluated and analyzed.Specific research results are as follows:（1）The design scheme of Cu-based composite powder with spraying temperatures of600℃,700℃,and 800℃was proposed.The ceramic particles with organic Mosaic,uniform component distribution,sphericity,and good fluidity were obtained by the methods of ball milling,spray granulation,and sintering.The efficient deposition of Cu-Ti₃Al C₂composite coating was achieved by cold spraying technology.The coating has a dense structure,stable phase,high bonding strength,less oxidation inclusion,minimum porosity of 0.58%,maximum hardness of 397.1 HV_0.5,and maximum bonding strength of 51.4 MPa.（2）The mechanical properties of the coating are mainly related to the density.Increasing the spraying temperature can effectively increase the microhardness and bonding strength of the coating.Microstructure defects such as porosity and microcracks of the coating affect the conductivity of the coating.The microstructure defects of the coating are mainly related to the spraying process parameters.Increasing the spraying temperature is beneficial to increase the density of the coating and promote the deposition of ceramic particles.Tensile strength test results show that the coating is mainly mechanically bonded,and cracking failure occurs inside the coating.The measured bonding strength values mainly represent the cohesive strength of the coating.The bonding strength of the Cu-Ti₃Al C₂-800℃composite coating is51.4 MPa,and the coating resistivity is the lowest,reaching 2.28 mΩ·mm.（3）Reciprocating current-carrying friction and wear testing machine was used to test the friction and wear characteristics of the coating.The experimental results show that compared with the friction behavior of Cu-Ti₃Al C₂-600℃and Cu-Ti₃Al C₂-700℃composite coatings,Cu-Ti₃Al C₂-800℃composite coatings effectively improve the wear resistance of the contact surface.Under dry friction conditions,the wear volume of Cu-Ti₃Al C₂-800℃composite coating is the lowest,which is 10.6×10^-3mm³,and the wear resistance is the best.Under the condition of 2A current load,the fatigue wear of the coating becomes lighter,and the wear volume of the Cu-Ti₃Al C₂-800℃composite coating is the lowest,which is 6.9×10^-3mm³,and the wear resistance is the best.Under the condition of low current,the friction surface of Cu-Ti₃Al C₂composite coating is smooth,the wear volume is less,and the wear resistance of the coating is good.With the further increase of the current,the fatigue wear on the surface of the material is aggravated,and the wear volume of the coating increases.