Improved, relatively low-cost method has been developed to produce porous metals with predetermined pore size, pore spacing, and density, utilizing powder-metal processes. The method uses angular not spherical tungsten powder

Todd, H. H.

English

NASA Technical Reports Server

November 1968	 Brief 68-10528 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Method for Controlling Density and Permeability of Sintered Powdered Metals 
An improved, relatively low-cost method has been 
developed to produce porous metals with predeter-
mined pore size, pore spacing, and density, utilizing 
powder-metal processes. The need for such materials 
exists for a number of applications such as contact 
ionizers, transpiration and ablative cooling, boundary 
control surfaces, and fluid filters. With this method, 
the pore size, shape, and spacing are predetermined by 
adding an inert volatile material of the desired pore 
size and geometry prior to pressing and sintering. 
The method was developed during experiments with 
tungsten powders to produce porous tungsten ionizers. 
Initially, closely sized spherical tungsten powders were 
compacted and sintered to make the porous material. 
High cost of the spherical powders and technical 
difficulties in producing a low-density material with 
controlled pore size and spacing led to investigation 
of other methods. 
This method utilizes sized, hydrogen-reduced, angu-
lar tungsten powders costing much less than spherical 
powders and having particle sizes that can be readily 
controlled during manufacture of the powders. The 
method of producing the desired material is as follows: 
1. Metal powders of selected size are blended with 
relatively inert particles that will give pores of 
the desired size and geometry. The final density 
is determined principally by the amount of inert 
material incorporated in the metal powder. In 
actual practice, flake copper has been utilized as 
the inert material, and has been blended with 
angular tungsten powder of 0.8 micron average 
size. 
2. The metal powder mixture is pressed hydrostati-
cally to produce a compact of the desired size and 
shape.
The pressed compact is presintered at a tempera-
ture sufficiently high to produce grain growth and 
densification in the powder mass surrounding each 
inert particle, but at a temperature below the melt-
ing or volatilization temperature of the inert 
particles. Tungsten powderfi ake copper mixtures 
for example are presintered in the temperature 
range of 1850 11
 to 1950°F, which is below the 
melting point of copper, but above the minimum 
sintering temperature of the tungsten powder 
compact. This procedure results in the establish-
ment of a sintering pattern within the tungsten 
powder surrounding each inert particle. 
Upon completion of presintering, the temperature 
is raised sufficiently to evaporate the pore-forming 
inert particles and produce the desired densifica-
tion of the pressed compact. 
5. Machining the compact to final dimensions is 
accomplished by infiltrating the porous compact 
with copper or the more inert gold, machining to 
the desired geometry, and reevaporating the infil-
trated metal at high temperature in vacuum. 
Porous compacts of less than 70 percent theoretical 
density were produced in sizes of up to 4 X 2 X ½ 
inch. 
Note: 
Documentation is available from: 
Clearinghouse for Federal Scientific and 
Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: B68-10528
(continued overleaf) 
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=19680000484 2020-03-12T06:31:55+00:00Z
Questions concerning this innovation may also be 
directed to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B68-10528
Patent status: 
No patent action is contemplated by NASA. 
Source: H. H. Todd 
of Electro-Optical Systems, Inc. 
under contract to 
Lewis Research Center 
(LEW-10393) 
Brief 68-10528	 Category 03


Method for controlling density and permeability of sintered powdered metals

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server