Directed light fabrication of refractory metals and alloys Page: 4 of 23
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Directed Light Fabrication of Refractory Metals and Alloys
Joe C. Fonseca
Gary K. Lewis
Patrick G. Dickerson
Ron B. Nemec
Group MST-6
Materials Science and Technology Division
Los Alamos National Laboratory
Los Alamos, New Mexico, 87545
Abstract
This report covers work performed under Order No. FA0000020 AN
Contract DE-AC12-76SN00052 for deposition of refractory pure metals
and alloys using the Directed Light Fabrication (DLF) process and
represents our progress in depositing these materials through September
1998.
In extending the DLF process technology to refractory metals for
producing fully dense, structurally sound deposits, several problems have
become evident. 1. Control of porosity in DLF-deposited refractory metal
is difficult because of gases, apparently present in commercially
purchased refractory metal powder starting materials. 2. The radiant heat
from the molten pool during deposition melts the DLF powder feed nozzle.
3. The high reflectivity of molten refractory metals, at the Nd-YAG laser
wavelength (1.06pm), produces damaging back reflections to the optical
train and fiber optic delivery system that can terminate DLF processing.
4. The current limits on the maximum available laser power to prevent
back reflection damage limit the parameter range available for
densification of refractory metals.
The work to date concentrated on niobium, W-25Re, and
spherodized tungsten. Niobium samples, made from hydride-dehydride
powder, had minimal gas porosity and the deposition parameters were
optimized; however, test plates were not made at this time. W-25Re
samples, containing sodium and potassium from a precipitation process,
were made and porosity was a problem for all samples although
minimized with some process parameters. Deposits made from potassium
reduced tungsten that was plasma spherodized were made with minimized
porosity. Results of this work indicate that further gas analysis of starting
powders and de-gassing of starting powders and/or gas removal during
deposition of refractory metals is required."' ._.'i'" s?-3 ;""-.. ti:.'"" ,TS..7 :Rir.+"l. . . '.}"ST"'4 ... -z ti -',' .' PR ".'.:"sI. -. '.4^- .. r;, "-t,,. _. _ .
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Fonseca, J. C.; Lewis, G. K.; Dickerson, P. G. & Nemec, R. B. Directed light fabrication of refractory metals and alloys, report, May 30, 1999; Los Alamos, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc707906/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.