Creep characteristics of molybdenum at high temperature and stress are utilized to compress tungsten foil liner against inner surface of tantalum alloy cylinder to form bond at interface. Temperature and pressure can be accurately controlled and size of workpiece is limited only by furnace size

Maag, W. L.

Mattson, W. F.

English

NASA Technical Reports Server

December 1970	 Brief 70-10723 
S	 NASA TECH BRIEF 
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 subscription basis from the National Technical Information Service, Springfield, 
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nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Improved Method for Cladding the Inside of Metal Tubes 
Tantalum Alloy 
Molybdenum Mandrel  
High-Pressure 
Gas
Or OP
Tungsten Foil
CM 
0 
The problem: 
To combine two concentric cylinders of different 
metals into one composite cylinder. Specifically, to 
apply a thin tungsten lining on the inside surface 
of a tantalum alloy cylinder. 
The solution: 
Utilize the creep characteristics of molybdenum at 
high temperature and stress to compress the tungsten 
liner against the inner surface of the tantalum alloy 
cylinder and form a bond at the interface. 
How it's done: 
Several layers of one-mu-thick tungsten foil are 
wrapped around the outside of a tubular molyb-
denum mandrel and inserted into a tantalum alloy 
cylinder of slightly larger diameter. The assembly is
placed in a furnace and the molybdenum tube con-
nected to a high pressure gas source outside the 
furnace. The furnace is heated to a high temperature 
(typically 3000F) and the molybdenum tube is 
internally pressurized according to a predetermined 
schedule. Under the high temperature and stress, 
the weaker molybdenum creeps diametrically until 
its outside surface contacts and compresses the 
tungsten against the stronger tantalum alloy outer 
cylinder. This process firmly bonds the tungsten 
layers to each other and to the tantalum alloy 
cylinder. The molybdenum mandrel is then dissolved 
in an acid solution that does not react with the 
tungsten and tantalum alloy, leaving the tungsten-
lined tantalum alloy cylinder. Alternatively, the man-
drel can be removed by machining. 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
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This new compression bonding method is superior 
to previous bonding methods for the following 
reasons: (1) The temperature and pressure can be 
accurately controlled to ensure uniform bonding 
conditions, regardless of size; (2) the size of the 
work piece is limited only by the furnace size; 
(3) the equipment is readily available and relatively 
inexpensive; (4) the dimensional tolerances between 
the two concentric cylinders are not critical; and 
(5) the bonding process can be performed at any 
temperature high enough to cause creep of the man-
drel material. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B70-10723
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to: 
Patent Counsel 
Mail Code 500-311 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Source: W. L. Maag and W. F. Mattson 
Lewis Research Center
(LEW-1 1174) 
Brief 70-10723	 Category 08


Improved method for cladding the inside of metal tubes

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