Study Of Properties Controlling Of Nickle-Base Alloy Formed By Laser Additive Manufacturing

Laser additive manufacturing technology is a new processing technology that uses high-energy laser beam as heat source to melt metal powder or wire material and directly manufacture solid parts by means of layer upon layer stacking.It has the advantages of simple,efficient and strong adaptability,and has been widely used in industrial manufacturing,aerospace,medical and other aspects.Nickel-based superalloy is a metal material that can work stably under high temperature.It has excellent high temperature strength,oxidation resistance and good ductility.But the traditional process to manufacture high temperature alloy workpiece is easy to cause serious damage to the cutting tools,and the workpiece shape is also very limited.The laser additive manufacturing technology can be used to solve the processing problem of nickel-based superalloy.But the laser additive technology is easy to cause the inhomogeneity of mechanical properties because of the heat input and the directional growth of crystals.Therefore,in view of the roughness of the structure and uneven mechanical properties in the laser additive manufacturing process,the processing technology,structure and properties of Inconel625 nickel-based superalloy were studied in this paper.In addition,ultrasonic vibration was simultaneously applied and refiners were added to the powder to refine the structure of the formed parts and improve the mechanical properties.In this paper,the additive manufacturing process of Inconel625 alloy was systematically studied,and the influence law of each process parameter on the forming was determined through the single channel deposition test.The study showed that the single channel melting width of the forming part was most affected by the laser power,the melting height of the sedimentary layer was most affected by the powder delivery rate,and the sedimentary layer was most affected by the line energy.Inconel625 alloy laser additive manufacturing process parameters are selected in the following range,forming well:laser power 1500-2000W,line energy 150-200J/mm,powder delivery rate 12-20g/min,at this time,the melting width of single channel deposition is 2.5-3mm,the deposition height is 0.2-0.35mm,and the melting depth is 0.1-0.25mm.The microstructure of Inconel625 alloy fabricated by laser additive is mainly epitaxial columnar crystal and equiaxed crystal structure through multiple deposition layers,which is mainly composed of?-(Fe,Ni)solid solution rich in Ni,Cr,Mo and Fe.The micro-hardness of the formed part is between 250-300HV_0.1,the yield strength is up to 400MPa,higher than that of the casting,the tensile strength is up to 515MPa,and the impact toughness is up to 45J/cm².In order to improve the microstructure and mechanical properties of laser additive manufacturing,synchronous ultrasonic vibration was applied in this paper.The research shows that ultrasonic vibration is applied on the basis of the laser additive manufacturing process.Under the same laser process parameters,the ultrasonic power is set at 800W and the frequency is 50k Hz.The number and length of the epitaxial columnar crystals were decreased when the grain was refined obviously by the laser additive with ultrasonic vibration.The hardness reached 322.5 HV_0.1 on average,which was nearly 20%higher than that of the formed parts without ultrasonic vibration.The yield strength reached 517.57MPa,the tensile strength reached 730.09MPa,the elongation rate reached 27.4%,and the section shrinkage rate reached14.46%.Compared with the formable parts without ultrasonic vibration,both of them were significantly improved.The impact toughness of the formed part reaches 56.67J/cm²,which is nearly 30%higher than that of the laser additive without ultrasonic vibration.The microstructure and mechanical properties of Inconel625 alloy with 1%Ti C powder were studied.The microstructure of the Ti C/Inconel625 alloy formed by laser additive was significantly refined,and the number and size of the epitaxial columnar crystal were significantly reduced.In addition to the solid solution of?-(Fe,Ni),Ni₃(Ti Nb)and Ti C particles precipitated from the matrix were also present in the grain boundary of the matrix.The mean value of hardness reached 285.2HV_0.1,which was 8%higher than that of pure Inconel625 alloy,but the change range of hardness value was reduced.The yield strength increased significantly,reaching 500.54MPa,a relative increase of 37.9%,and the yield strength reached 582.39MPa,a relative increase of 13%.The impact toughness reached 41.67J/cm²,basically equal to that of pure Inconel 625 alloy.