Title:
Alloys and process of making same
United States Patent 2119488


Abstract:
" " 15 Clahns ( S The present invention relates to the production Sof hard metal alloys, and it particularly relates ' U to the production of alloys which may be uti" /. lized for making various types of cutting tools. Swear-resisting implements, and so forth. It has been proposed to make...



Inventors:
Padowicz, Henry N.
Application Number:
US9373336A
Publication Date:
05/31/1938
Filing Date:
07/31/1936
Assignee:
Sirian, Wire And Contact Compan
Primary Class:
Other Classes:
419/11, 419/14, 419/31, 423/274, 427/217, 428/403
International Classes:
B22F1/02; C22C1/05
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Description:

" " 15 Clahns ( S The present invention relates to the production Sof hard metal alloys, and it particularly relates ' U to the production of alloys which may be uti" /. lized for making various types of cutting tools.

Swear-resisting implements, and so forth.

It has been proposed to make -hard metal bodies from combinations of tungsten carbide and cobalt which are sintercd together at temperatures bctwccn 1500' C. and 1600' C. It has 10 been found, however. that the hard metal alloys produced according to these processes. although quite expensive and difficult to manufacture. nevertheless are not fully satisfactpry in their hardness and wearing .qualitIes.

S It Is among the objects of the present nenion to prepare an imtprovcd lii iea-tlloY strength. hardness and density. which may be nmade of uniform quality from batch to batch.

*0 and which will have a sufficient degree of toughness and density to enable its-wide utiiZation In connection with wear-resisting implements. cutting tools',and s forth.

Other objects will be obvious and will appoar 1 during the course of the following specificationIn accomnplishing the objects of the present invention it has been found most suitable to prepare a mixture of finely divided carbides of refractory metals, said mixture preferably in-O cluding two or mnore of the following carbides: titanium carbide, tungsten carbide, tantalum carbide, vanadium carbide, thorium carbide, molybdenum carbide, uranium carbide, columbium carbide, and chromium-.carbide. Thdse carbldes .' are usually best prepared by obtaining the finely divided metal in pure condition, the metal being most preferably prepared by reduction in a hydrogen atmosphere in an electric furnace.

These finely divided refractory metals are pref49 erably carburized by heating them .with flnc] divided carbon, preferably- of the tye knowr as sugar carbon, in a reducing atmosphere I an electric furnace, which reducing atmosphemay desirably inc!Ude hydrocarboh gases Sucl . as acetylene, ethylene, methane, and so forth These finely divided carbides are -then mixei together in the dcs.ired proportIons to prod the dcz!rcd amon!lt a! ree-ctry ,ult' . final ha*rd metal alloy.

A!nnn the preferreCd proportionS.-are betwee of...ai.... .nadi. andOr chrO mh.ar- carbidc hetvec .o 6 5c.,5 of tungs:e carb-de: and -ctW-.cn 10% to 25%; Of tanta!u: carvid1- here chronium carbide is also ir cludld. it may replace the titanium or van, ·Ii· ~ierral L~u dium. or It may be utilized in the amount of between 1% and 5%.

It has been found desirable to combine these carbides with substantial amounts of cobalt, iron and/or nickel, and this may be done by adding the finely divided carbide mixture to a solu-. tion. slurry or liquid dispersion of the water soluble, organic cobalt or nickel compound. This method of combining nickel and cobalt with the carbides is more fully described and set orti.. in co-pending applcaUon Serlal.Nýoý3.134. filed July 31st. 1936.' In the prferred procedure described nsaid co-pending applicat ., %he pulverized and finely. divided :carblde mixture -is added to a con-cen- 1 co--. . alt " . .. - . = oblt a et.e - L l ieCU .. ro- all bth-e-cobtlacetate it-is-posslbe~o- use other soluble.S. t-;uch as cobalt sulpate. cobalt chloride; or obalt.nitrate, and preferably-the cobalt.-salt is used in the form of a concenttedatr. U;M.ted -'wt tio.hc hLO be saturated and even carry s uspended pticles of the cobalt salt or even Insoluble cobalt compounds in suspension.

SIn lieu of some or all of the cobalt-compound or compounds above mentioned it is posslble to include the corresponding iron or nickel compounds.

The proportioning of the refractory meta, or of the additional metal such as cobalt, nickel or iron. or of the carlbon, s preferably such that. the final refractory metal will constitute between 50% to 80% of the alloy, or in some instances between.about 88%t:.90%:-of the aloy;hie the additional metal .- will. constitutt beteen. Sabout 10%: .and 11% :.qf tihe alloy, or n.some Instances more thami 25%-.of-,thc alloyi; w;hile .thbe carbon will' conitte .p to.2%' to03%'I -of .the. alloy, and .een u . to. 10 . . to  4..50i l n ...... instances. -.-- : . -In preparing the alloy, frm A ..the carb .. mi ture and solution of the caaetate, the fely divided carbides are mixed or milled together Sand are t.en -prmilo :.'nt t he cobalt-acctzat solution. The liquid .is evaporated away with Sstirring until a dry solid.mass is obtained. This solid mas, may then be finov.l ground and subSjected to reduction, most desirably in an electric furnac. in .. hvdrogen . atmopb(nhre. After thin reduction operation has been- completed the re_ sultant mass "may b formed or ,,resed to drsirrd shapes and then sintered to foam the finIshed article ready for commercial use in cut- 5 --lr- ---d U ting tools, drawing dies, wear-resisting parts, and so forth.

The following are several typical examples of carbide mixtures which may be prepared for incorporation with the cobalt or nickel salt solution, said carbides being preferably produced by reduction or carburization in a hydrogen atmosphere: Example 1.-In parts by weight: 5 of titanium carbide, 63 of tungsten carbide, 20 of tantalum carbide, and 2 of vanadium carbide.

Example 2.-In parts by weight: 4 of titanium carbide, 1 of chromium carbide, and 84 of tungsten carbide.

Example 3.---In parts by weight: 2 of chromium carbide, 35 of tungsten carbide, and 53 of tantalum carbide.

Example 4.-In parts by weight: 38 of titanium carbide, 470 of tungsten carbide, 150 of tantalum carbide, and 15 of vanadium carbide.

Example 5.-In parts by weight: 30 of tungsten carbide and 60 of tantalum carbide.

Example 6.-In parts by weight: 3 of chromium carbide, 5 of titanium carbide, 5 of thorium carbide, 10 of molybdenum carbide, 20 of tungsten carbide, and 20 of tantalum carbide.

'Example 7.-In parts by weight: 30 of titanium carbide, 8 of chromium carbide, and 636 of tungsten carbide.

Example 8.-In parts by weight: 15 of chromium carbide, 260 of tungsten carbide, and 400 of tantalum carbide.

In each case these carbides have been preferably prepared by carburizing the finely divided, pure metal with sugar carbon in a hydrogen atmosphere for two hours-at a temperature of 1200' C. to 1600* C. The meta!-:r ders.may be separately carburized or they may be mixed together before carburization. These metal powders after carburization are milled for a couple of days, preferably without balls, to give a finely divided mixture having a fineness exceeding 180 mesh.

According to one desirable process of combination, the milled carbide mixture of Examples 4, 7, or 8 is sieved through a 180 mesh screen or sieve and then sprinkled into a solution of 370 parts by weight of crystallized cobalt acetate in 1,000 parts by weight of water.

Of course the cobalt may be replaced in part or whole by equivalent quantities of nickel or iron salts. The solution containing the cobalt acetate is then evaporated to dryness with constant stirring and the residue is dried for about ten hours and then thoroughly pulverized so that it may be bolted through a 180 mesh screen.

This powder is then loaded into nickel boats and reduced in a hydrogen atmosphere in an electric, furnace according to the following schedule: Held / hour at 20 volts Held 13, hours at 50 volts Held 1/4 hour at 70 volts Held /4 hour at 100 volts Held 1% hours at 130 volts The temperature then reaches about 600 C., which is maintained until reduction is complete.

The boats are then pushed into the cooler and allowed approximately fifteen minutes to cool. 70 The final product, which is in the form of a very fine powder, is then formed under pressure to the desired shape. The formed pieces are then placed in carbon tubes and heated in a hydrogen atmosphere in an electric furnace to approxi75 mately 14500 C. for thirty minutes or longer, dependent upon the size of the pieces. The tubes are then pushed into the cooler and when cold they are withdrawn.

Although the high temperature treatments, namely the carburizing, the reduction, and the sintering, are carried out in reducing atmospheres, it has been found most suitable to carry out the carburizing in a hydrocarbon atmosphere, while the reduction and sintering operations are carried out in a reducing atmosphere, preferably of hydrogen.

The present application is particularly directed to the combination of mixtures of refractory metal carbides with cobalt or nickel, with the cobalt or nickel being in the form of a water soluble organic salt compound. The process of combining a refractory metal carbide with a solution of cobalt acetate or other cobalt or nickel salts is more fully described and claimed in copending application Serial No. 93,734, filed July 31st, 1936. It is also possible to combine finely divided refractory metal powder with the metallic carbides before such metallic carbides are combined with the cobalt acetate solution.

Processes in which the tungsten or other refractory metal is combined in finely divided form with the cobalt or nickel salt, are more fully described and claimed in co-pending application Serial No. 93,171, filed July 29, 1936.

Many other changes could be effected in the particular features of process treatment disclosed, and In specific details thereof, without substantially departing from the invention intended to be defined in the claims, the specific description herein merely serving to illustrate certain elements by which, in one embodiment, the spirit of the inventfion may be TIee i '.ft-d --.

What I desire to claim is: 1. A process of preparing hard metal alloys which comprises combining a finely divided mixture of refractory metal carbides and then combining this mixture with a water solution of an organic salt of an additional metal selected from the group consisting of iron, nickel and cobalt, said water solution being concentrated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere.

2. A process of preparing refractory metal alloys which comprises combining a mixture of finely divided carbides of refractory metals with a water solution of an organic acid salt of cobalt, said water solution being concentrated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in. a reducing atmosphere.

3. A process of preparing hard metal alloys which comprises combining a mixture of tungsten and tantalum carbides with a water solution of an organic acid salt of cobalt, said water solution being concentrated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere.

4. A process of preparing hard metal alloys which comprises combining a mixture of tungsten and tantalum carbides with a water solution of an organic acid salt of nickel, said water solution being concentrated and being evaporated down to dryness wnie continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere.

5. A process of preparing hard metal alloys ¢* *' which comprises carburizing a mixture of at least two refractory metals, and then combining the mixture with a water solution of an organic acid salt of cobalt, said water solution being concen6 trated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere. 6. A process of preparing hard metal alloys which comprises carburizing tungsten and tantalum with sugar carbon, milling the carbides, sifting the carbides through a 180 mesh screen, and combining the carbides with a water solution of an organic acid salt of cobalt, said water solutlon being concentrated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere.

7. A process of preparing hard metal alloys which comprises milling together carbides of tungsten and tantalum, sifting the carbides through a 180 mesh screen, and combining the carbides with cobalt, said combination being effected by sprinkling the sifted carbides into a concentrated solution of cobalt acetate, evaporating to dryness with agitation, reducing the dried mixture and sintering.

8. A method of making hard metal alloys which comprises combining together at least two finely divided refractory metal carbides selected from the group consisting of titanium, tantalum, tungsten, chromium, uranium, molybdenum, thorium and vanadium, and combining said carbides with a water solution of an organic acid salt of cobalt, said water solution being concentrated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere.

9. A method of making hard metal alloys which comprises combining together at least two finely divided refractory metal carbides selected from the group consisting of titanium, tantalum, tungsten, chromium, uranium, molybdenum, thorium, vanadium, and sprinkling said carbides 4into a concentrated cobalt acetate solution, evaporating said solution to dryness with agitation, powdering, reducing the powder in a hydrogen atmosphere, forming the reduced powder, and sintering.

50 10. A process of producing refractory metal alloys which comprises combining together finely divided refractory metal carbides and the finely divided refractory metals, and then combining Sthis mixture with a water solution of an organic 65 acid salt of cobalt, said water solution being concentrated and being evaporated down to dryness while continually stirring, the dry material being pulverized and sifted and then reduced in a reducing atmosphere. 11. A hard metal alloy comprising about 90% of a mixture of tantalum and tungsten carbides, and about 10% of a mixture of nickel and cobalt, the particles of the carbide being each encased in and cemented together by a coating of nickel and cobalt, said alloy being prepared by mixing the carbides with a salt solution of the encasing metal, followed by evaporating, drying, pulverizing, reducing, compressing and sintering.

12. A hard metal alloy comprising about 90% of a mixture of tantalum and tungsten carbides, and about 10% of cobalt, the carbide particles being each encased in and cemented together by a cobalt coating, said alloy being prepared by mixing the carbides with a salt solution of the encasing metal followed by evaporating, drying, pulverizing, reducing, compressing and sintering.

13. A process of,producing a hard metal alloy which comprises evaporating a slurry containing and reducing the resultant mixture of finely divided cobalt acetate, tungsten carbide and tantalum carbide, forming, and sintering, the carbide particles being each encased by cobalt acetate before reduction.

14. A hard metal alloy consisting of finely divided tungsten and tantalum carbides, the particles of which are each encased in, and cemented together by, a coating of an additional metal selected from the group consisting of iron, cobalt and nickel, said alloy being prepared by mixing the finely divided tungsten and tantalum-carbides with a solution of a water soluble salt of the additional metal to form a slurry followed by reduction to dryness with constant agitation, reduction of the dried mixture in hydrogen and sintering.

15. A hard metal alloy consisting of finely divided tungsten and tantalum carbides, the particles of which are each encased in, and cemented together by, a coating of an additional metal selected from the group consisting of iron, cobalt and nickel, said alloy being prepared by mixing the finely divided tungsten and tantalum carbides with a solution of a water soluble salt of the additional metal to form a slurry followed by reduction to dryness with constant agitation, reduction of the dried mixture in hydrogen and sintering, said tungsten carbide being utilized in greater proportion than the tantalum carbide.

HENRY N. PADOWICZ.

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