Study On Processing And Properties Of Spherical Metal Powder Prepared By Plasma Rotating Electrode Process

Selective electron beam melting(SEBM)has the advantages of high utilization rate of energy,fast scanning speed and no pollution in vacuum environment,provided new possibilities for metal materials used in aerospace,such as high strength stainless steel,titanium alloy and nickel-based superalloy.Spherical metal powder is the key to application of SEBM technology.Among all the processes,powders prepared by plasma rotating electrode process(PREP)has a smooth surface and good sphericity,presents few satellite and hollow powders,which basically meet the requirements of SEBM technology for metal powder.However,the size of powders made by PREP is coarse,and the properties of powders which has different sizes are different.Therefore,it is of great significance to systematically study PREP process,powder properties and its influence on performance of samples.In this paper,three kinds of spherical metal powders of high strength stainless steel,Ti-6A1-4V and Inconel 718 were prepared by PREP method.Combined with powder formation process and droplet breaking mechanism,the optimum process was determined by controlling parameters,such as electrode rotational speed,current intensity and feed rate.The SEM,XRD and Microhardness tester and other analytical methods were used to characterize the powder properties of different particle sizes.Ti-6Al-4V powders(<150 ?m)were used as the raw material for SEBM technology.The main conclusions are as follows:(1)The electrode rotational speed affects average particle size(D50).D50 decreases as the electrode rotational speed increases.When the materials are different and the electrode rotational speed is same,D50 is related to the value of ?/?Tm,the smaller ?/pTm is,the smaller D50 is.The current intensity and the feed rate mainly affect the concentration of the particle size distribution.As the current intensity or the feed rate decreases,the particle size distribution is narrowed and D50 does not change.(2)The optimal preparation process of three material powders are:high-strength stainless steel powder:electrode rotational speed is 18000 r/min,current intensity is 1700 A,feed rate is 0.8 mm/s;Ti-6Al-4V powder:electrode rotational speed:18000 r/min,current intensity:1750 A,feed rate:1.0 mm/s;Inconel 718 powder:electrode rotational speed is 18000 r/min,current intensity is 1500 A,and the feed rate is 0.8 mm/s.(3)As the particle size decreases,the fluidity of powder first increases and then decreases,the bulk density and tap density decrease,and the oxygen content increases.When the particle size range is same,the fluidity values,bulk density and tap density of different materials are mainly related to the theoretical density of the material.The particle size of powder affects the surface morphology,microstructure of cross-section,phase composition and microhardness of the powder,the smaller particle size of the powder,the finer of the crystal grains and the higher of the hardness.(4)The relative density of Ti-6Al-4V alloy(particle size:-100 mesh)prepared by SEBM is as high as 99.62%,and the microhardness is 348.27 HV,which is higher than that of Ti-6Al-4V alloy prepared by traditional methods.