Process is accomplished by reducing tungsten hexafluoride with hydrogen. Metallic tungsten of essentially 100 percent purity and density is produced and built up as dense deposit on heated mandrel assembly. Process variations are building up, sealing or bonding refractory metals at temperatures below transition temperatures of base metal substrates

Kahle, V. E.

Lewis, W. J.

Stubbs, V. R.

English

NASA Technical Reports Server

Jul 1971	 Brief 71-10212 
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a aubscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Fabrication of Large Tungsten Structures by Chemical Vapor Deposition 
Process details have been developed for the fabrica-
tion of a large, pure-tungsten, rocket-motor chamber 
shell (or similar geometric structure). The process in-
volves the chemical vapor-phase deposition of tung-
Graphite Mandrel with Tungston Screen Assembled 
sten, which is accomplished by reducing tungsten 
hexafluoroide, WF6 , with hydrogen, 1­12: 
WF 6
 + 31-1 2 - W + 6HF 
Metallic tungsten of essentially 100e purity and 
dciisitN is produced In this reaction and is bu It up as
a dense deposit on a heated mandrel assembly. 
The initial fabrication step is to machine a block 
of graphite into a mandrel having an external con-
figuration and dimensions corresponding to the inside 
dimensions of the desired tungsten structure. The 
graphite mandrel is then spirally wrapped with strips 
of tungsten mesh, and electrical resistance heating 
elements are inserted into predrilled holes in the 
graphite. The assembly, which is mounted to rotate 
about its vertical axis (axis of symmetry) in an evacu-
ated vapor-deposition retort, is heated to approx-
imately 617 K (650° F) and slowly rotated adjacent 
to a contoured spray nozzle. A metered gaseous mix-
ture of hydrogen and tungsten hexafluoride (which is 
a gas at room temperature) is sprayed from the nozzle 
onto the heated rotating mandrel. As the gas mixture 
contacts the hot outer surface of the wrapped mandrel, 
the tungstçn hexafluoride is reduced by the hydrogen, 
and pure metallic tungsten is uniformly deposited on 
the surface of the tungsten mesh wrapping. The dep-
osition process is continued until all voids in the mesh 
are filled and the desired thickness of the reduced 
tungsten is deposited. Unreacted WF6 is removed 
from the exhaust gases by a cold trap, after which the 
gases are bubbled through a lime solution to neutralize 
the HE The completed assembly is removed from the 
retort and the graphite mandrel is separated by 
machining, leaving a tungsten shell structure of the 
required shape and thickness. 
Notes: 
I. A shell with dimensions 13.33 cm (5.25 in.) diam-
eter at the small end, 40.6 cm (16 in.) diameter at 
the nozzle exit, and 61 cm (24 in.) length, is the 
largest structure of this type kno n to have been 
constructed to (Lite. ftc shell SCI\ cd as the liner 
untied on etleal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000211 2020-03-17T02:19:14+00:00Z
wall of a regeneratively cooled hydrogen-fluorine 
rocket thrust chamber. 
2 Fabrication of the tungsten shell is another ap-
plication of the chemical vapor deposition process 
summarized in NASA Tech Brief B67-10232. Vari-
ants of this process can generally be used to build 
up, seal, or bond refractory metals at temperatures 
well below the transition temperatures of the base 
metal substrates. 
3 The following documentation may be obtained 
from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NASA-C R-72742 (N71-14135), Investigation 
of Advanced Regenerative Thrust Chamber 
Designs
4. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B71-10212 
Patent status: 
No patent action is contemplated by NASA. 
Source: V. R. Stubbs, W. J. Lewis, and

V. E. Kahle of

Aerojet-General Corp.

under contract to

Lewis Research Center

(LEW-1 1239) 
Brief 71-10212	 Category 04,08


Fabrication of large tungsten structures by chemical vapor deposition

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