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Spheroidisation of metal powder by pulsed electron beam irradiation.

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Title: Spheroidisation of metal powder by pulsed electron beam irradiation.
Authors: Murray, J.W.1 (AUTHOR) james.murray@nottingham.ac.uk, Simonelli, M.1 (AUTHOR), Speidel, A.1 (AUTHOR), Grant, D.M.1 (AUTHOR), Clare, A.T.1 (AUTHOR)
Source: Powder Technology. May2019, Vol. 350, p100-106. 7p.
Subjects: Electron beams, Metal powders, Stress waves, Irradiation, Grain refinement, Transmission electron microscopy
Abstract: A new powder spheroidisation process has been demonstrated using a large-area, pulsed electron beam technique. This was used to dramatically improve the surface morphology of Stellite 6 metal powder. Powder surface asperities up to 20 μm size can be eliminated by melting and incorporation into the near-surface of the particle. Surface finish is significantly improved. Agitation and rotation of particles due to a beam-induced stress wave enables the irradiation of multiples sides of particles, resulting in uniformly smoothed particles after sufficient pulses. Elemental analysis revealed no measurable contamination as a result of the process. Transmission electron microscopy showed a dense layer is produced within a zone up to 3 μm beneath the surface, with a substantially reduced grain size from ca. 2 μm diameter in the bulk to ca. 40 nm. Elemental homogenisation also was accompanied by grain refinement. The irradiated Stellite 6 showed a reduced basic flowability energy (583 mJ compared to 627 mJ for the untreated), explained by reduced particle-particle cohesion and interlocking, and an increased conditioned bulk density of 4.57 g/ml compared to 4.33 g/ml due to satellite/asperity reduction. Unlabelled Image • Metal powder spheroidisation by pulsed electron beam was demonstrated for the first time on Stellite 6. • Sa roughness was reduced from 218 to 95.7 nm. • Irradiation causes rotation and hence uniform smoothing. • Basic flowability energy was reduced from 627 to 583 mJ. • Conditioned bulk density was increased to 4.57 g/ml after irradiation from 4.33 [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:A new powder spheroidisation process has been demonstrated using a large-area, pulsed electron beam technique. This was used to dramatically improve the surface morphology of Stellite 6 metal powder. Powder surface asperities up to 20 μm size can be eliminated by melting and incorporation into the near-surface of the particle. Surface finish is significantly improved. Agitation and rotation of particles due to a beam-induced stress wave enables the irradiation of multiples sides of particles, resulting in uniformly smoothed particles after sufficient pulses. Elemental analysis revealed no measurable contamination as a result of the process. Transmission electron microscopy showed a dense layer is produced within a zone up to 3 μm beneath the surface, with a substantially reduced grain size from ca. 2 μm diameter in the bulk to ca. 40 nm. Elemental homogenisation also was accompanied by grain refinement. The irradiated Stellite 6 showed a reduced basic flowability energy (583 mJ compared to 627 mJ for the untreated), explained by reduced particle-particle cohesion and interlocking, and an increased conditioned bulk density of 4.57 g/ml compared to 4.33 g/ml due to satellite/asperity reduction. Unlabelled Image • Metal powder spheroidisation by pulsed electron beam was demonstrated for the first time on Stellite 6. • Sa roughness was reduced from 218 to 95.7 nm. • Irradiation causes rotation and hence uniform smoothing. • Basic flowability energy was reduced from 627 to 583 mJ. • Conditioned bulk density was increased to 4.57 g/ml after irradiation from 4.33 [ABSTRACT FROM AUTHOR]
ISSN:00325910
DOI:10.1016/j.powtec.2019.03.041