Research On Preparation Of Spherical W And W-ZrC Powders By RF Induction Plasma Spheroidization

Tungsten has excellent properties such as high melting point,high hardness and low thermal expansion coefficient,and is widely used in medical,military and nuclear industry and other fields.However,due to the low ductile-brittle transition temperature of tungsten,it is difficult to prepare precision tungsten components by traditional machining,which limits its further wide application.In recent years,the development of metal 3D printing technology has provided a new way for the manufacture of tungsten complex components.The performance of feedstock material tungsten powder is a key factor in determining the quality of tungsten components in additive manufacturing.With the improvement of densification requirements for tungsten components,the requirements for particle shape and particle size of tungsten powder also increase.In this paper,the tungsten powder is spheroidized by the radio frequency induction plasma spheroidization technology,and the high-performance spherical W powder and W-ZrC powder are finally obtained by optimizing the process.The detailed research contents are as follows:Firstly,from the perspective of the degree of agglomeration,the mechanism of the different spheroidization effects of commercial hydrogen-reduced tungsten powders with different particle sizes is analyzed,and the effect of different spheroidization process parameters(plasma power,powder feeding rate)on the tungsten powder was studied,and the optimal process parameters were obtained;then,the hydrogen-reduced tungsten powder was pre-treated by spray granulation process,and the influence of different parameters(pH value,solid content,etc.)on the viscosity and stability of the ball milling slurry were analyzed,and the differences in morphology and particle size of granulated W powder and granulated W-ZrC powder under different process parameters(solid content,atomizer speed,etc.)were studied;finally,the improvement of the spheroidization effect of tungsten powder by spray granulation pretreatment was investigated.The main conclusions are as follows:(1)The 6μm and 8μm hydrogen-reduced tungsten powders have a high degree of agglomeration,more heat is required for complete melting of agglomerate particles,and the spheroidization effect is poor.With the increase of particle size,the degree of powder agglomeration gradually decreased,and the spheroidization effect gradually increased.When the plasma power was 60 k W and the powder feeding rate was 50g/min,the spheroidized flowability of 20μm commercial hydrogen-reduced tungsten powder was 6.28 s/50g,and the apparent density was 9.36 g/cm~3.(2)pH value,solid content,dispersant addition and ball milling time of the slurry determine the stability and uniformity of the slurry by affecting the distribution of powder particles.The atomizer speed determines particle shape and particle size of the granulated powder.Under the optimal process parameters,granulated W powder and granulated W-ZrC powder with average particle sizes of 26.946μm and 23.970μm were prepared by spray granulation treatment.(3)The pretreatment of spray granulation is beneficial to the preparation of high-performance spherical W powder and spherical W-ZrC powder.The flowability of spherical W powder and spherical W-ZrC powder after spheroidization is 5.95s/50g and 7.17 s/50g respectively,and the apparent density is 10.21 g/cm~3 and 8.94g/cm~3 respectively.