US1633258A - Refractory metal alloy of high density and high melting point and method of making the same - Google Patents

Description

with the refractory metal.

. base metal when introduced therein.

-metal so as to produce Patented June 21., 1921.

UNITED STATES PATEN cnmlr nus A. men, or nawon'rn;

REFRACTORY METAL No Drawing.

My invention relates to useful-alloys of refractory metals of high 'density.and of high melting point combined with base metals of much lower density and lower melting point, and process for'producing the same. I

Such metallicbodies are very useful in the arts where the metal of the bodies is subjected to considerable wear such as bearings, electrodes for spot-welding, switchboard contacts, etc., and this is especially true when alloys of high electrical and heat conductivity and high density are desired, and which do not soften and disintegrate at high temperatures.

The metals, tungsten and tantalum, for instance, are well known to be refractory metals having these characteristics, and when alloyed with the basemetals, nickel, silver, aluminum, copper, cobalt, etc., result in theproduction of the required me,- tallic bodies useful for the purposes above stated.

In general the melting points of the alloys known in the art are lower than either of the melting points of their constitutents. The alloys, however, which I produce by my process are characterized by their melting points are ,higher than the melting points of the base metals alloyed Alloys of these metals have heretofore been very difiicult to produce by means known to the art for the reason that the heavy refractory metal has a tendency to settle to the bottom of the bath of molten f I have discovered that a. Emore or less orous body of refractory metal of Ifigh densit and high melting point, when broug t into. contact with a molten body of a base metal of much lower density andmelt'ing oint for which it'has alloying aflinity, It will absorb, that base metal andin the arts for many useful purposes.

In order to efi'ect the alloying of the metals as described, such a. physical struc ture of the compressedrefractory body must first be determined so that it has the greatest possible sary also to absorbing power of the body of refractory alloys of various comf. positions. This, I- have discovered, can be absorbing power. Itis 'neces-i determine how to regulate the phere,

the fact that fractory compressed body, and

by reduction of "sten powder'which is m or most-desirable to use should have a 'QOU-mesh'sieve and theni'jthor u l'y-g by weig t nn'rnon or MAKING THE same.

Application filed mm a,- 1925. Serial Ko. 61,164.

done by first adding small percentages of either boron or carbon'to the powdered refractory metal, and then baking in an atr OFFICE. I

annoy ornmn DENSITY Ann ,nrsn'nnnrmeroiitr m) .1

'mosphere of hydrogen at a'temperat'ure of vapproximately about 900 degrees 'to IOOO'dcgrees centigrade. During this baking the additions artially-combine, with the hydrogen thus orming a porous body. 1

When the powders of tun 'sten or of tantalum are to be compressetibetter results are obtained ,by the addition of small p er-' centages of boron nitride or other refractory nitrides, such as titanium, tantalum, vanadium, chromium, silicon, etc.

During the baking operation to which these compressed bodies are to be subjected either in a vacuum ora reducing atmoswhich will be hereinafter more specifically referred to, thenitrides partially decompose, thereby liberating nitrogen and thus addingto the porosity and absorbing power of the compressed bodfy.

In the carrying out 0 my process, whether the refractory metal be tungsten or tantalum, and whether the base metal be the basev metals above specified.

any one of I proceed as follows:

In the interest of clearness the production of a tungsten-copper alloy will be described, but it is to be distinctly understood that an analogous procedure will produce an alloy of any other selected refractory metal and any other selected base metal.

My invention divides itself into two parts: I

First: Productionof a suitable porous re- Second: In the alloying lowernielting point base metals by tion in a molten vacuum or a reduclng atmosphere.

Describing then the'production of tungsten-copper alloy, I first prepare a pure light orv flufiy tungsten powder, preferably of said bod weight of about 35,110 45 grams inch. This powder is then sifted is uniformly mixed; with'.5% 601% the pure oxide with a mix 'ture of hydrog n and ammonia, as well known inthe art; or, infact, I may use any bath of said "metals inisto be used. This pressure should preferably be as low as possible yet suflicient for' the body to take the sha of the mold'and to be subsequently han led without break- -ing, and a pressure of from two to five tons er square inch is usually amply suflicient or this purpose. The compressed bodies are then removed from the mold and baked at an initial temperature of from 700 degrees to 800 de ees centigrade, which temperature is pre erably increased slowly for a period of approximately ten minutes to 1000 degrees centigrade, and continued at that temperature for another period of approximately ten minutes either in-a vacuum has been immersed in the be or 'a reducing or inert atmosphere. The

7 body is then allowed to cool in the same atmosphere. This baking ste causes a partial decomposition of the a issions resulting in a porous body. When a refractory nitride is used, the liberated nitrogen adds to the porosity of the compressed body, and

consequently to its power of absorption, while at the same time the baking of the body strengthens it so that it can be readily handled without danger of breaking} It has been found that certain re actory nitrides, such as vanadium nitride and chromium nitride also have the additional function of toughening and hardening the final alloy.

After the compressed bodies are baked and cooled, as above described, they are immersed in a bath of molten copper, either in a vacuum or in a hydrogen or other reducing atmosphere, for a, period of one hour, the molten copper being kept at a temperature as close to the melting point thereof as possible. a

An effective means for immersing these bodies is to sus end them from supports of tungsten or ot er refractory wire so that when the period of alloying has expired they may be quickly lifted out of the bath by means of the supports and quickly cooled. The outer adhering film of copper on the body isthen eith er machined off or removed by chemical means well known in the art.

As above stated, after the porous body t of molten base metal, it is permitted to remain in the said bath long enough for the molten constituents to seep through the porous refractory body and fill up the pores and alloy 1,ese,2:se

with the refractory constituents. While, as stated, the operation may be performed either in a vacuum or in a reducing atmosphere, either of hydrogen or mixtures of drogen and nitrogen, it is found prefer- Having thus described my invention what- I claim as new and desire to secure by Letters Patent is:

1. A metallic body comprisin a (porous compressed mass of tungsten and a ecomposed nitride of refractory metals, and a base metal filling the pores of said mass.

2. A metallic body comprising a porous, compressed mass of decomposed tungsten and boron nitrides, and nickel or copper filling said pores.

3. A method of producing-refractory alloys, which comprises absorbing molten metals in' compressed bodies of tungsten interspersed with decomposed boron.nitride.

4. A method of producing refractory alloys, which comprises abosrbing molten metals and molten alloys in compressed bodies of tungsten interspersed with decomposed refractory nitrides.

5. A method of making porous bodies of refractory metal, which comprises compressing said metal with a nitride of a refractory metal, and decomposing said nitride in said mass at a high temperature. p

6. The steps in the production of an allo of refractory metal with a base metal whic consists in mixing with the refractory metal small additions of refractory particles decomposable at a high temperature, com: pressing said mixture into a shape, baking the same to partially. decompose said additions to form a porous bod 7. The steps in the method of producing an alloy of refractory metal with a base metal which consists in mixing with the refractory metal small additions ofboron nitride, compressing said mixture into a shape baking the same to partially decompose sai baron nitride to form a porous body.

8. The method of producing an'it-llo of refractory metal with a base metal which consists in mixin with the refractory metal small additions 0 boron nitride, com ressing said mixture into a shape, baking t e same to partially decompose said boron nitride to orm a porous body, then immersing the. porous body in a molten bath of a base metal.

tungsten and copper whic an alloy of consists of thoroughly mixing small percentages of re- .fractory nitrides into a mass of tungsten powder, compressing said powder into a body .of suitable shape, baking the compressed body at about 700 to 800 degrees centigrade, increasing said temperature to approximately 1000 degrees centigrade, then immersing said bod in molten copper, removing said body trom said bath and removing the copper from the surface of said body.

9. A method of producing 10. A method of producing an alloy of tungsten and copper which consists of preparing flufiy tungsten powder by reduction of a tungsten compound with a mixture of hydrogen and ammonia, sifting said powder through a QOO-mesh sieve, uniformly mixing .5% to .1% of boron nitride with said powder, compressing said body into the shape desired, baking said body in a reducing atmosphere, immersing said body in a bath of molten copper in an inert atmosphere.

CLEMENS A. LAISE.