Metal Powder for Additive Manufacturing
Metal Powder for Additive Manufacturing
M. QIAN ma.qian@rmit 0
0 1.-School of Aerospace, Mechanical and Manufacturing Engineering, Centre for Additive Manufacturing, RMIT University , Melbourne, VIC 3001 , Australia. 2.-
Metal additive manufacturing (AM) processes are
poised to transform the metal manufacturing
industry, particularly in those areas where
conventional manufacturing reaches its limitations in
terms of both design freedom and manufacturing
capabilities. Many metal AM systems are available
today, including the powder-bed, powder-fed, and
wire-fed processes based on laser, electron beam or
plasma melting. At the same time, the variety of
metal powder materials suitable for AM continues
to expand. Currently there are 29 common metal
powder materials available for AM, including
stainless steels, aluminum, nickel, cobalt-chrome,
and titanium alloys.1 The articles selected for this
focus topic of JOM under Metal Powder for Additive
Manufacturing are largely focused on metal powder
for powder-bed fusion AM processes.
The importance of metal powder characteristics in
the powder-bed fusion AM processes has become
increasingly recognized. How the powder flows and
packs, can have a significant impact on powder bed
formation, and hence the development of melt pools
and microscopic homogeneity. Excessive variations
in powder characteristics can lead to nonuniform
layering, inconsistent bulk density, increased
defects, undesired mechanical properties, and poor
surface finish. As a result, it is essential to be able to
identify the various powder characteristics that can
ensure consistent and reliable performance,
particularly when a lower cost, less spherical powder is
intended for AM.
In the first article, Slotwinski and Garboczi
discuss the metrology needs for metal AM powders.
The authors provide an informative overview of the
current technical challenges and needs in
characterizing metal powders for AM, processes based on
laser, electron beam or plasma melting including
recent efforts to standardize characterization
Ma Qian is the guest editor for the Powder Materials Committee the TMS
Materials Processing and Manufacturing Division (MPMD), and
coordinator of the topic Metal Powder for Additive Manufacturing (3D
Printing) in this issue.
methods in the ASTM International (ASTM) and
the International Organization for Standardization
(ISO), such as the recently released ASTM F3049,
Standard Guide for Characterizing Properties of
Metal Powders Used for Additive Manufacturing
In the second article in this compilation, Clayton
et al. show the necessity of appropriate metal
powder characterization for AM through four case
studies, and the inability of conventional
characterization techniques to detect the subtle
differences. These four case studies deal with (I)
quantifying batch-to-batch variation in feedstocks,
(II) the influence of different suppliers and
manufacturing methods, (III) the effect of additives
on feedstock properties, and (IV) process-relevant
differences between fresh and used feedstocks.
These are all important issues in metal AM.
The third article by Strondl and co-workers is
concerned with the characterization and control of
powder properties for AM. The authors discuss the
combined use of powder rheology and dynamic
image analysis to characterize metal powders for AM.
This study adds another useful case study to metal
powder characterization for AM.
In the fourth article in this sequence, Tang et al.
report on the effect of powder reuse times on the AM
of Ti-6Al-4V using an Arcam EBM A2 system
(Arcam AB, Mo¨lndal, Sweden). Parts manufacturers
are always both quality- and cost-conscious. In metal
AM processes, the powder reuse times directly affect
the affordability of the additively manufactured
parts. Hence, it is necessary to identify the effect of
powder reuse times on the AM process and the
mechanical properties of the alloy thus fabricated.
The powder composition, particle size distribution,
apparent density, tap density, flowability, and
particle morphology were studied as a function of
powder reuse times and compared with respective
properties of the virgin Arcam Ti-6Al-4V powder.
Detailed tensile mechanical property data were
produced from samples fabricated using Ti-6Al-4V
powder that had been reused 16 times. The samples
showed highly consistent tensile properties,
irrespective of their locations in the powder bed.
In the context of the AM of titanium, the high cost
of titanium metal powder used for AM has been a
concern for the wider applications of Ti AM.
Lowering the cost of the feedstock titanium metal
powder is thus desired. In the fifth article by Sun et al.
the authors discuss the use of a Commonwealth
Scientific and Industrial Research Organisation
(CSIRO) proprietary technique to manipulate a
novel titanium powder precursor. The manipulated
titanium powder was characterized using various
techniques, including the utilization of an external
powder bed system, which contains an identical
powder feed and raking system to that used in an
Arcam A1 EBM machine. The manipulated low-cost
titanium powder in the size range of 75–106 lm was
found to behave very similarly to reused Arcam
Ti-6Al-4V powder in such an external powder bed
In the sixth and final article in this collection,
Tong et al. provide a concise summary of recent
efforts to produce fine spherical
high-niobium-containing TiAl alloy powders. A compact process was
proposed and demonstrated by the authors for the
preparation of microfine spherical
high-niobiumcontaining TiAl alloy powders.
In summary, this selection of articles highlights
different aspects of metal powder feedstock
materials for AM and offers a snapshot of the current
1. J.F. Isaza and P.C. Aumund-Kopp , Powder. Metall. Rev . 3 , 41 ( 2014 ).