Study on behaviors of tungsten powders in radio frequency thermal plasma

Zhu, Hailong; Tong, Honghui; Cheng, Changming; Liu, Geoffrey

doi:10.1016/j.ijrmhm.2017.01.017

Cited by 26 publications

(3 citation statements)

References 30 publications

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“…The powder feedstock needs to have su cient owability in order to ensure that the powder adequately spreads along the build plate during the EB-PBF process. The more spherical particle geometries result in better owability and powder packing which consequently increases the powder bed density and improves the properties of fabricated parts [34][35][36][37]. Therefore, the powder feedstock to the EB-PBF process is recommended to be provided in spherical geometries.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Virgin, Recycled, and Oxygen-reduced Copper Powders Processed by the Plasma Spheroidization

Sehhat

Cullom

Newkirk

2022

Preprint

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Copper powder in three different powder types were spheroidized using radio-frequency inductively coupled plasma (ICP) spheroidization process (TekSphero-15 system). The characterized powders include virgin powder as purchased from the powder manufacturer, powder used in electron beam powder bed fusion (EB-PBF) process, and reconditioned powder, which was used powder that underwent an oxygen-reduction treatment. The goal of spheroidizing these powder types was to evaluate the change in powder morphology, the possibility of enhancing the powder properties back to their as-received conditions, and assess oxygen reduction of the powder lots given their initial oxygen contents. Also, to investigate the impact of re-spheroidization on powder properties, the second round of spheroidization was performed on the already used-spheroidized powder. The impact of powder type on powder sphericity and particle size distribution was evaluated using the image analysis of scanning electron microscope (SEM) micrographs and laser diffraction, respectively. The spheroidized powder showed higher sphericity and more uniform particle size distribution overall. Depending on the powder collection bin, second round of spheroidization affected the powder sphericity differently. The possibility of deploying the plasma spheroidization process as an alternative oxygen-reduction technique was also investigated through tracking the powders’ oxygen content using inert gas fusion method before and after the spheroidization. The plasma spheroidized powder showed less oxygen content than the hydrogen-treated powder. The second round of spheroidization caused no change in oxygen content. The correlation between oxygen-reduction and created cracks was discussed and compared between plasma spheroidization and hydrogen-treatment. The plasma spheroidization process created a powder with higher sphericity, uniform particle size, and less oxygen content.

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Section: Introductionmentioning

confidence: 99%

Characterization of Virgin, Recycled, and Oxygen-reduced Copper Powders Processed by the Plasma Spheroidization

Sehhat

Cullom

Newkirk

2022

Preprint

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“…Thermal plasma can be generated by different excitation modes. Radio frequency inductively coupled plasmas (ICP) have been successfully applied to tungsten spheroidization [13][14][15][16][17]. Li et al prepared fine-grained spherical tungsten powders with narrow particle size distribution by ICP torch [16].…”

Section: Introductionmentioning

confidence: 99%

Investigation on spheroidization of refractory tungsten powders by laminar DC plasma torch

Yang

et al. 2022

Mater. Res. Express

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The spherical tungsten powders were prepared by a low-power DC laminar plasma torch. At a discharge current of 50 A, the tungsten powder fed downstream cannot be spheroidized by using Ar discharge, while a small number of spherical particles can be observed with upstream feeding. When N2 is added to the working gas, the input power is increased to maintain the same discharge current, which leads to the increase of plasma jet length, thereby expanding the effective high temperature region. Optical emission spectroscopy measurements show that the electron excitation temperature of N2-Ar mixed discharge is higher than that of argon discharge. In addition, compared with argon plasma, N2-Ar mixed gas plasma has larger thermal conductivity due to the molecular dissociation. Therefore, the heat is more efficiently transferred from the plasma to the tungsten particles. The improvement of plasma jet and heat transfer characteristics by introducing nitrogen into the discharge contributes to the increase of spheroidization rate. EDS analysis shows that the oxygen content in the tungsten particles decreases after spheroidization, which is caused by the evaporation of tungsten oxide during plasma treatment.

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“…At present, RF inductively coupled plasma spheroidization is recognized as the first choice for fabricating spherical tungsten powder due to its high temperature and high enthalpy [ 19 , 20 , 21 , 22 , 23 ]. The mechanism of RF inductively coupled plasma spheroidization is shown in Figure 1 .…”

Section: Introductionmentioning

confidence: 99%

Research on Spheroidization of Tungsten Powder from Three Different Raw Materials

et al. 2022

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In this work, three kinds of tungsten powders with different particle sizes were spheroidized by radio-frequency (RF) inductively coupled plasma spheroidization. The spheroidization behavior of these tungsten powders was investigated and compared. The spheroidization effects of irregular tungsten powder improves with the decrease in degree of agglomeration and increases with primary particle size. Spherical tungsten powder from irregular powder with a primary particle size of 19.9 μm and an agglomeration coefficient of 1.59 had the best spheroidization effect; its apparent density, hall flow time, and spheroidization ratio are 9.36 g/cm3, 6.28 s/50 g, and 98%, respectively. The results show that irregular feedstock tungsten powder with a smaller primary particle size and higher agglomeration degree has a poor spheroidization effect because it is easily affected by the gas flow and deviates from the high temperature zone. On the contrary, irregular feedstock tungsten powder with larger primary particle sizes and lower agglomeration degrees has better spheroidization effects.

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Study on behaviors of tungsten powders in radio frequency thermal plasma

Cited by 26 publications

References 30 publications

Characterization of Virgin, Recycled, and Oxygen-reduced Copper Powders Processed by the Plasma Spheroidization

Characterization of Virgin, Recycled, and Oxygen-reduced Copper Powders Processed by the Plasma Spheroidization

Investigation on spheroidization of refractory tungsten powders by laminar DC plasma torch

Research on Spheroidization of Tungsten Powder from Three Different Raw Materials

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