Design And Research Of Mo-based Conductive And Wear Resistant Coating Deposited By Supersonic Plasma Spraying

Conductive and wear-resistant components have been applied to improve the surface performance of sliding electrical contact parts in high-end equipment.In recent years,the rapid development of electronic communication,rail transit and aerospace has further promoted the research and application of products.With the development of resource-saving society,the application of surface coating technology to improve the conductive and wear resistance of equipment parts has become a hot technology with low cost consumption and various functions.At present,researchers mainly improve the conductive and wear resistance of the coating by adopting appropriate coating preparation technology and special material system components,and satisfy its performance requirements under special working conditions.This paper analyzed the failure of Current-carrying friction elements under actual harsh service conditions,and then the new powder material coatings were prepared by thermal spraying technology to improve the comprehensive protection performance of parts.The Mo-Zr-Ti-Re material system powders were designed and fabricated.The spraying parameters of coatings were optimized.Mo-based coatings were fabricated on Cu alloy substrates by supersonic plasma spraying.During spraying,a Spray Watch 2i system was used to monitor the velocity and temperature of in-flight particles.Scanning electron microscopy(SEM)was used to investigate the microstructure.Transmission electron microscope(TEM)was used to detect the phase composition.The hardness,elastic modulus and fracture toughness of the coatings were measured by a high-precision macro/micro-indentation tester using Vickers diamond indenter and the crack extension region in the coatings were explored.The cohesion strength of the coatings was measured,the fracture failure type of the coatings was analyzed.The tribological properties of the coatings were evaluated.The residual stress and electrical conductivity were measured.Finally,the failure of coatings under actual working conditions were analyzed.(1)A new component of powder material system(Mo-Zr-Ti-Re)that was sprayed by supersonic plasma spraying technology with the unique high-velocity and high-temperate performances was determined.The Mo-Zr-Ti、Mo-Zr-Ti-3%Re、Mo-Zr-Ti-6%Re and Mo-ZrTi-12%Re powders were fabricated.The powders exhibit the spherical morphologies and the particles size were approximately 10～80 μm.The velocity and temperature of Mo-based particles are about 433 m/s and 2698℃,respectively.(2)BSE images were utilized to observe the microstructure of the coatings cross-sectional.The results showed that the Mo-based coatings exhibit the dense microstructure,little cracks and partially melted.The interface of the coatings and substrates is compact,and no stripping phenomena are observed.The Mo-Zr-Ti-Re coatings are composed of bright and grey areas corresponding to Re-rich and Re-poor microstructure areas.The Mo-Re alloy phase was formed in the Mo-Zr-Ti-Re coating.(3)The increase of Re element improved the cross-sectional hardness,porosity,surface hardness and elastic modulus of the coatings.The fracture toughness of Mo-Zr-Ti-6%Re coating is 4.31 MP m1/2,which is the highest.The fracture toughness of Mo-Zr-Ti-12%is 4.26 MP m1/2.The observation of the crack around the indentation by BSE images shows that Re-rich areas changed the crack propagation path.When the cracks encountered the Re-rich regions,the crack formed obvious deflection and secondary cracks.At the same time,the failure occurred within the coating layers,and the later process optimization results showed that the cohesion strength of the coatings reached up to 40.7 MPa when the substrate temperature was 150℃.The residual stress of four were residual compressive stress.And add Re element decline the conductive.(4)The increase of Re content made the average friction coefficient and wear amount of the coatings decrease.There are flake on the wear surface of the coating,and there are obvious plastic deformation,furrow and adhesive wear and a small amount of oxidation in the wear process.EDS indicates that the Al grinding is mainly due to the peeling off of the coating material.(5)With the increase of Re element content,the friction coefficient and wear rate of the coating were decreased.In the process of friction,a mass of adhesive wear and severe oxidation occurred on the worn surface,and ablation phenomenon were occurred on the wear surface of Mo-Zr-Ti-6%Re coating.At the same time,the increase of Re elements leads to the severe wear of Al pin surface.