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Metallurgical and Materials Transactions B

, Volume 35, Issue 5, pp 937–948 | Cite as

The role of particle size on the laser sintering of iron powder

  • A. Simchi
Article

Abstract

The effects of powder particle size on the densification and microstructure of iron powder in the direct laser sintering process were investigated. Iron powders with particle sizes ranging from 10 to 200 µm were used. It was found that the sintered density increases as the laser energy input is increased. There is, however, a saturation level at which higher density cannot be obtained even at very intensive energy input. This saturation density increases as the size of the iron particles decreases. Meanwhile fine powders with narrow particle size distributions have a tendency toward agglomeration, and coarse powders with broad particle size distributions have a tendency toward segregation, both of them resulting in lower attainable density. In order to investigate the role of particle size, a “densification coefficient (K)” was defined and used. This coefficient depends on the particle size and the oxygen content of iron powder. The results of this investigation demonstrate that the presence of oxygen significantly influences the densification and pore morphology of laser-sintered iron. At higher oxygen concentrations, the iron melt pool is solidified to agglomerates, and formation of pores with orientation toward the building direction is more likely to occur. When the oxygen concentration is kept constant, the densification coefficient decreases with decreasing the particle size, meaning the densification kinetics enhances. This article presents the role of powder characteristics and the processing parameters in the laser sintering of iron powder as a model material. The mechanism of particle bonding and microstructural features of laser-sintered parts are addressed.

Keywords

Material Transaction Iron Powder Sintered Density Coarse Powder Powder Particle Size 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

C1, C2

constants in Eq. [2]

D

densification, Eq. [4]

d

thickness of layer, mm

h

scan line spacing, mm

K

densification coefficient, Eqs. [2] and [5]

MPS

mean particle size, µm

P

laser power, W

T

temperature

ν

scan rate, mm/s

ρbed

density of powder bed, pct theoretical

ρls

density of laser-sintered specimen, pct theoretical

ρst

saturation density, pct theoretical

ρtab

tap density, pct theoretical

γ

surface tension, Nm s−1

ω

laser energy input per volume of sintered specimen, kJ/mm3

ϕ

agglomeration factor, ρ bed/ρ tap

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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2004

Authors and Affiliations

  • A. Simchi
    • 1
  1. 1.the Department of Materials Science and EngineeringSharif University of TechnologyTehranIran

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