Ti6Al4V表面石墨-B4C复合涂层激光合金化磨削OA

Ti6Al4V titanium alloy is widely recognized as a metallic material with outstanding comprehensive performance,encompassing high specific strength,superior corrosion resistance,and excellent biocompatibility.Owing to these synergistic advantages,it demonstrates irreplaceable significance across a broad spectrum of high-demand fields,ranging from aerospace(e.g.,aircraft structural components and engine parts)and military engineering(e.g.,precision weaponry and armor systems)to marine engineering(e.g.,offshore platform components and deep-sea exploration equipment)and biomedicine(e.g.,orthopedic implants and dental prostheses).While,in practical applications,Ti6Al4V components often encounter challenges such as complex stress environments,friction and wear,and corrosion.Their surface properties largely determine the overall service performance and service life of the components.Traditional machining methods,such as grinding,milling,turning,are often utilized to realize the surface finishing.However,the mechanical properties of the machined surfaces can not be guaranteed.So the heat treatment methods including carburization,nitriding quenching,laser quenching,and even shot peening are applied to strengthen the surface.It should be noticed that the extra residual stress,the microstructure content and the surface precision become worse under heat treatment.The integrated machining-strengthening technology avoids damage to the surface morphology and is gradually replacing the traditional laser coating technology to realize efficient performance-precision synergistic manufacturing of Ti6Al4V surfaces.However,the existing methods are only applied to pure graphite coatings,and the comprehensive performance of carburized Ti6Al4V surfaces are resistant to meet the demand.Therefore,this study extends the integrated machining-strengthening method to different content graphite-B4C composite coatings and proposes a laser-alloyed grinding to achieve boron-carbon strengthening of Ti6Al4V surfaces.Comparative experiments are conducted to investigate the effects of B4C content on the thermal conductivity of the coating,homogeneity of the molten pool,and the microphase composition,morphology accuracy and mechanical properties of the alloyed surfaces.The composite coating containing 25%B4C has excellent thermal conductivity.A flat alloyed surface(surface roughness Sa=3.3)with uniform microphase composition is obtained after laser-alloyed grinding.Granular and acicular precipitates give the alloyed surface high hardness(900HV)and wear resistance.Although the carbon element can enhance the surface hardening effect by sacrificing the corrosion resistance property,the boron element can be an extra supplement for a better comprehensive property characteristic.However,when the content of B4C in the coating is excessively high,both the microscopic phase composition and macroscopic morphology of the coating become inhomogeneous,thereby leading to a decrease in hardness,wear resistance,and corrosion resistance of the machined surface.Moreover,the coating's laser energy absorption rate and thermal conductivity decrease,and consequently,the substrate material undergoes uneven heating.With the further increase in B4C content,the surface morphology of the molten groove deteriorates,and the formation of crack and porosity defects occurs within the alloyed molten pool.Laser-alloyed grinding enables performance-accuracy synergistic manufacturing of boron-carbon strengthened Ti6Al4V surfaces and promotes the integrated machining-strengthening method to industrial practice,which is vitally important in the field of anti-fatigue manufacturing of titanium alloy.