Jan_AMP_Digital

21 / 78

A D V A N C E D
M A T E R I A L S
&
P R O C E S S E S | J A N U A R Y
2 0 1 6
2 1
it may be beneficial to perform these
comparisons before making additively
manufactured structural parts.
In addition, tensile specimens
could have been manufactured to near-
net size to reduce specimen preparation
time and cost. The z orientation (vertical)
specimens could have been manufac-
tured to net size, allowing for a compar-
ison between as-manufactured surfaces
and smooth machined surfaces. This
comparison may be important for parts
with significant fatigue loading.
Fatigue curves were not generat-
ed. Instead, parts were subjected to a vi-
bration acceptance test, which showed
that the parts would be sufficient for
the specific mission, but did not lead
to a standard stress-versus-cycles (S-N)
curve that could be used for other parts
and applications. Vibration acceptance
and/or fatigue curve generation should
be considered if fatigue loading is a con-
cern in other applications.
Testing of three non-HIP’d tensile
specimens suggests that HIPing may not
be necessary to achieve desired strength
levels. ASTMF3055 requires the sameme-
chanical properties for Class D (stress re-
lieved, HIP’d, solution treated, and aged)
and Class F (same as Class D, except no
HIPing) parts. Results described here
support this, but there were not enough
specimens to make a complete compari-
son on the effect of HIPing.
Finally, now that industry standard
ASTM F3055 is available for use, it may
be easier to standardize manufacturing
processes from different vendors. All of
the parts in this application were made
consecutively by one vendor, but this
may not be possible in a large produc-
tion environment. ~AM&P
For more information: Andrew Clifton
is an associate manager in Structur-
al Materials and Processes, Lockheed
Martin Space Systems Co., 1111 Lock-
heed Martin Way, Sunnyvale, CA 94089,
408.742.1502,
.
References
1. J.J. Schirra, R.H. Caless, and R.W.
Hatala, The Effect of Laves Phase on
the Mechanical Properties of Wrought
and Cast + HIP Inconel 718, 1991
Superalloys Conference Proceedings,
2. G.F. Vander Voort, G.M. Lucas, and
E.P. Manilova, Metallography and Mi-
crostructures of Heat-Resistant Alloys,
in ASM Handbook, Volume 9: Metallog-
raphy and Microstructures, p 837, ISBN
0-87170-706-3.
Fig. 8 — Orion Exploration Flight Test 1 vehicle in the Pacific Ocean after landing. Courtesy of
NASA.
Fig. 7 — Build pause on vertical tensile specimen. Build direction is left to right.