Study On Cu TiB₂ Conductive Wear-resistant Coating By HVOF

Copper matrix composites are widely used in tram pantograph skateboards,integrated circuit lead frames and other fields.copper matrix composites improve the strength of pure copper,often accompanied by a decrease in conductivity.increasing the strength of copper matrix composites while maintaining a higher conductivity,which is conducive to meet the increasing requirements for the comprehensive properties of the materials.TiB₂ particles have high hardness and TiB₂ have high conductivity compared to most ceramic particles,which is of concern as the enhanced phase of copper matrix composites.Cu powder,Ti powder and B powder were used as raw materials to prepare spray powder by mechanical alloying.dense Cu based TiB₂coating was prepared on copper plate substrate by supersonic flame spraying.thermodynamic calculation and DSC differential thermal analysis were carried out on the system.The effects of spraying process parameters and the content of enhanced phase on the microstructure,mechanical and electrical properties of the composite coating were studied.scanning electron microscope,energy spectrum analyzer,X ray diffraction and other methods were used to analyze the microstructure of the coating,and the mechanical properties,friction and wear properties and electrical conductivity of the coating were detected in turn.The results of thermodynamic calculation show that Gibbs free energy is the lowest TiB₂the Cu-Ti-B alloy system is formed,can be generated in situ in the alloy systemAs a result,after 4 hour of mixed powder milling,it was refined to form agglomerated particles.the powder size was generally uniform,and no oxides,borides and other impurities were produced in the ball milling process.coating thickness is about 200?m,and the coating section has obvious rheological layered structure.When the ratio of oxygen to fuel flow is 3?1,the Cu₃Ti decomposes Ti can obtain a small amount of TiB₂.through diffusion and B reactions.With the increase of the ratio of oxygen and gas flow,the density of the composite coating first increased from 99.05%to 99.08%and then greatly decreased to 97.54%.Reducing the proportion of Ti powder and B powder in the raw material powder can improve the compactness of the composite coating to a certain extent.As the ratio of oxygen and gas flow increases,the hardness of the Cu-2%(Ti+2B)composite coating decreases slightly first and then greatly,and the conductivity of the coating always shows a downward trend.When the ratio of oxygen and fuel flow is 2?1,the microhardness of the composite coating is 543HV,the conductivity is 59.4%IACS,which is the best proportion of oxygen and gas flow.Under the optimum spraying process parameters,when the proportion of Ti powder and B powder in the raw powder decreased from 6%wt to 2%wt,the density of the coating increased from 98.83%to 99.05%the microhardness decreases from 566HV to 543HV,the friction coefficient increases from 0.24 to 0.27,the wear rate also increases,the microhardness and the friction and wear performance decrease slightly,but the conductivity of the composite coating is greatly improved,and the conductivity is increased from 32.2%IACS up to 59.4%IACS.