Goldstein, J. I.

Romig, A. D., Jr.

English

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120
2_:_;
N91-71218
POWDER METALLURGICAL COMPONENTS FROM LUNAR METAL
A. D. Romig, Jr. and J. I. Goldstein Dept. of Met.-Mats. Sci.,
Lehigh University, Bethlehem, PA 18015
INTRODUCTION
Assuming the eventual establishment of high technology colonies on the
moon, one may wonder what possible industrial goods can be produced at
these colonies using lunar resources. It is proposed that in such a
colony, with adequate but limited energy resources already developed,
industrial powder metallurgy components can be fabricated from native iron
alloys.
Free iron is readily available on the lunar surface, making up
approximately 0.045 st% of the regolith [2] (Fe, <.02-23 wt% Ni, <0.02-3.1 wt%
Co, < 0.02-11.5 wt%P, < 0.02-1.6 wt% S, and < 0.02-0.1 wt% Cr) [3]. Using a
regolith density of 0.9-1.1 g/cc [4], one can calculate that 3.9 x 10 I° metric
tons of Fe alloy are available in the top five cm. of the regolith. The
quantity woul0 be even larger if one considers greater depth and the
possibility of crushing larger rocks.
With the raw material available the appropriate manufacturing techniques
must be selected. Traditional processes such as casting, rolling, forging,
etc. are rejected because they are all very energy intensive procedures.
One viable alternative is powder metallurgical fabrication. It is a well
suited option since its energy requirements are not extravagant, iron metal
is readily available and a natural vacuum (2.7 x 1014 atm) [4] is already
present.
The components considered for fabrication will be smaller than i00 kg.,
probably less than i0 kg. It is not suggested that large structural
components can be fabricated in this manner. Proposed components cover a
broad spectrum of uses. Machine parts such as gears and cams are distinct
possibilities and are currently two powder metallurgy parts widely produced
on earth. Other possibilities include nuts, bolts, screws, connecting rods,
bearings, and electrical contacts. One distinct advantage of a powder
process is that the final product can be essentially fabricated in one step.
For example, a gear can be directly fabricated without subsequent machining.
Despite the cost required to develop a powder metallurgy facility, it
is thought that it is a better alternative than transporting all these
components from earth. The first technological problem is the collection of
the "ore." It may easily be collected by lunar roving vehicles with magnetic
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POWDERMETALLURGICALCOMPONENTSFROMLUNARMETAL
A. D. Romig, Jr.
121
skimming devices, and then transported to a central production facility.
By controlling the magnetic field strength of the skimming magnet and the
skimmer distance from the surface, one can restrict the gathered material to
highly magnetic metal and avoid collection of weakly magnetic minerals.
Metal Preparation and Part Fabrication - (see Figure 1 for a flow sheet.)
Initially the material will be mechanically sieved into various size
distributions. Following, it will be sent to a vibratory device to separate
the metal particles from any adjoining silicate. It is hoped that the low
temperature in the lunar shadows (-173 ° C) will somewhat embrittle the
material and assist in metal/gangue separation. The precise configuration
of such a separating device has yet to be determined. The retained gangue
must be kept at a minimum, since it will adversely influence the properties
of the finished component. A magnetic separator will then serve to
differentiate the metals from the gangue.
With powdered metal stock available, production may begin. One earth
...... _ ...... process Is hot compacting, w,mr_ compacting and sintering are
done simultaneously. Dies of air or oil hardened tool steel will be used,
and suitable production parameters would be T-800°C (>0.5 mp) (electrical
resistance heating), P-6.89 x 107 Pa (10,000 psi), and time-20 min.[5,6].
Another possibility, yet to be thoroughly investigated in the laboratory, is
to compact the powder in the ultrahigh lunar vacuum (ion-pump range). It is
possible that under these conditions, and with no oxide present on the surface
of the metal, the green compact will auto-sinter. The 100°C lunar daytime
temperature may assist this reaction. Various subsequent heat treatments
could be used to vary the components mechanical properties with design
requirements. For reference, Table 1 summarizes the mechanical properties
of pure Fe and a possible lunar alloy (both annealed) [7]. Realize that the
remaining traces of silicate will somewhat deteriorate the mechanical
properties of the lunar component, especially impact resistance. Fortunately,
Ni is a toughener when added to Fe, and one may still expect a suitable
finished product.
Following the basic production of the part, many subsequent procedures
are possible, including machining and welding.
Conclusions -
Once a high level colony has been established on the lunar surface,
lunar resources of free iron could be used to produce industrial components.
The raw material is plentiful and the quality of the finished goods should
be excellent. Proposed components would find uses in lunar machine manufac-
ture and maintenance. The production of large structural components (>100 kg.)
is not feasible with a lunar powder metallurgical process. If one wishes
to allow his mind to wonder, even the production of components for orbital
assembly of interplanetary spacecraft and orbital stations is technically
feasible.
122
POWDER METALLURGICAL COMPONENTS FROM LUNAR METAL
A. D. Romig, Jr.
f ini sh ing
mach in ing
we Id ing
etc.
Figure 1
Production Flow Sheet
sieve
separation mechanical
metal/gangue
separation
heattreatment
I auto-s intering_
J
magnetic sep.
metal from gangue
hot compacting
\
I compacting
Table I
Mechanical Properties of Lunar Alloys (annealed) [9]
Property
theoretical density
tensile strength
elongation
hardness
Not e :
Pure Fe Fe-5.Ni-0.5 C
> 95% > 95%
90 x 106 Pa 420 x l0 s Pa
(13,000 psi) (61,000 psi)
1.7% 5_
Rb 50
The other elements present, especially Ni, will
significantly increase the properties listed above.
POWDERMETALLURGICALCOMPONENTSFROMLUNARMETAL
A. D. Romig, Jr.
123
References
[i]
[2]
[33
[4]
Is]
[7]
Goldstein, J. I. and Axon, H. J., 1972, The Apollo 15 Lunar Samples,
p. 78-81, The Lunar Science Institute.
Goldstein, J. I., et al., 1972, Proc. Lunar Sci. Conf. 3 rd, p. 1037.
Goldstein, J. I. and Axon, H. J., 1973, Proc. Lunar Sci. Conf. 4th,
p. 751-775.
Taylor, S. R., 1975, Lunar Science: A Post Apollo View, p. 58,
Pergamon Press.
Stadtler, W. A., et al., 1969, "Powder Metallurgy," Vol. 4,
ASM Metals Handbook, p. 449-464.
Notis, M. R., 1976, personal communication, Lehigh University.
Smart, R. F., 1973, Developments in Powder Metallurgy, p. 19-57,
Mills and Boon Ltd.


Powder metallurgical components from lunar metal

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