US2119487A - Hard metal alloy and process of making the same - Google Patents

Description

Patented Maya, 1938 to Sirian Wire and Contact Company, Newark,

N. J., a corporation of Delaware No Drawing. Application July-31, 193e,

- Serial No. cause 12 Claims. (c 75-436),

The present invention relates to the produc salts, such as cobalt sulphate, cobalt chloride, or

tion of hard metal alloys and it particularly recobalt nitrate, or preferably the water soluble orlates to the production of alloys which may be ganic salts such as cobalt formate, cobalt tar-- utilized for making cutting tools, wear-resisting tiate, cobalt citrate, cobalt saccharate or cobalt implements of various sorts, and so forth. lactate, and desirably the cobalt salt is used in the 5 It has been proposed to make hard metal bodies form of aconcentrated water solution which may from combinations of tungsten carbide and cobe saturated and even carry suspended particles halt which are sintered together at temperatures of the cobalt salt.

. between -1500 C. and 1600 C. It has been found, In lieu of some or all of the cobalt compound or however, that the hard metal alloys produced accompounds above mentioned, it is possible to in- 1d cording to these processes are expensive and relaclude the corresponding iron or nickel comtively diflicult to manufacture and, are not pospounds. The proportioning of the hard metal, sessed of the most satisfactory qualities. such as tungsten, or .of the additional metal such It is among the objects of the present inven as cobalt, nickel or iron, orof the carbon, is preftion to prepare an improved, hard metal alloy at erably such that the refractory metal will con- 5 low cost and of high quality in respect tostrength, stitute between 50% to 80% of the final alloy, or hardness, homogeneity and density. Another ob; in some instances, between about 88% to 90% of 3601 is to provide an alloy which may be made the alloy; while the additional metal will constiuniform from batch to batch. Still another ob-" tute between about 10% and 11% of the alloy, or

.iect is to provide an alloy which will have a suflln s e i stan es, m than 2 of the alloy;

cient degree of toughness and density to enable while the carbon will constitute up to 2% t0 20 its wide utilization in .connection with wear-reof the a y, and even 119110 t0- 5% in c tai sisting bodies, cutting tools or working impleinstances.- v

ments which are 'to be employed in shaping or In preparing the alloy from the tungsten carcutting alloys of iron, t hr mokolrooc I bide and solution of the cobalt acetate, the fine- 25 halt. and sdforth. Other objects will become obly' divided tungsten carbide is mixed with the vious from inspection of the following pe ifi s,- cobalt acetate solution and is 'evaporated until a tion. Y paste or solid mass is obtained. This solid mass In' accomplishing the object of th present i maythen be finely ground and subjected to revention it has been found most, uitable t preduction, most, desirably in an electric furnace in a finely divided\ pulverized d d, ahydrog'en atmosphere. After this reduction optungsten or tungsten carbide, or a combination at n as b completed the t ntm ss of .both tungsten and. tungsten carbide. Tungmay ei m Dr t0 desired Shapes and stm carbide is preferably the predominant inthen sintered to form a finished article ready for 5 'gredient in the mass, or it should constitute the commercial u in cutting s. drawing e- ,entire mass to lee-processed. wear-resisting parts, and so forth.

'Although in the'preferred embodiment tung- Togive a specific example" of one manner of -sten carbide alone' is employed or compounded carrying out the present invention, a pure, fine with finely divided tungsten, it is also possible to tungsten powder is mixed with finely divided sug- 40 include in the combination or replace the tungor charcoal in the ratio of 184 parts of tungsten to so sten with other refractory metals, such as molyb 12 parts of carbon. This mixture is than fired d'enum, chromium,-ta ntalum; titanium, thorium, in a carbon boatin an inert or reducing.atmos 'columbium, uranium, either in the form of the phere at approximately 1450 C. for a length of finely divided metals or their carbides, or both. time suiiicient to form mono-tungsten carbide Mixtures of tungsten and tantalum carbides may from. the component materials. This material is as readily be employed. Where the carbides are emthen pulverized and milled. Cobalt acetate of ployed'the metal is preferably compounded in the the formulaCo(CalIaOz) 2.41 is then dissolved golpgrtion of one moi. of the metal to one moi. of in water to form a concentrated solution and placed in an evaporating dish. This solution is 5 -With, this pulverized and finely divlded -tungheated and the mono-tungsten carbide is sprin- 5o ,sten .carblde, with or without the additions above kled into it insmall quantities. This composite mentioned, is then mixed a concentrated solusolution is evaporated to dryness, with constant tion of acobalt salt, the preferred salt being a stirring, and the dried mass is then pulverized cobalt acetate. In lieu of a part or all of the coand sifted through a mesh sieve. This powder 55 bait acetate it is possible to use other soluble is then reduced inh'ydrogen. The resultant pow der is then pressed and formed in the desired shapes for use as cutting tools, ,drawing dies, sand blast nozzles, and so forth.

As another example of making this new alloy; pulverized, finely powdered mono-tungsten carbide corresponding to the chemical formula WC is added to a cobalt acetate solution. This'cobalt acetate solution is made by 'pulverizing C. P. cobait acetate (Co(C2HsO2)'2.4H2O) and then weighing and dissolving the required amount-in water to form a saturated solution. When the dissolution of the acetate has been completed, the solution is poured into an evaporating dish or other suitable container; In order to accelerate the process of dissolution of the acetate the, solution is heated. Tungsten carbide (W0) is then added in small quantities to this solution and'the whole is evaporated to dryness with constant stirring. This procedure takes approximately twenty hours. The resulting powder is sifted through-a 180 mesh sieve and reduced in an electric furnace in a hydrogen atmosphere. The temperature is gradually raised to 600 C. in approximately three hours and held there until reduction is complete. The resulting metal carbide powder made as above is then pressed and molded to the desired shapes. After sintering at suitable'temperatures from 1400" C. to 1550 C., the finished article is ready for commercial use, i. e.-, cutting tools, drawing dies, wean-resistant parts, and so forth.

As a third example of making this new alloy,

1104 grams of pure tungsten powder and '72 grams of sugar charcoal are milled together. The-mixture is loaded into carbon tubes and fired in an electric furnace with a reducing or hydrocarbon atmosphere, the temperature of the furnace being approximately 1450" C., which temperature is maintained for thirteen minutes. The material is then pushed into the cooling chamber with a reducing or hydrocarbon atmosphere and held there for approximately six minutes. The mono-tungsten carbide produced is crushed in amortar and milled. Then 666.8 grams of cobalt acetate C. P. (CO(C2H3O2) 2.41-120) are pulverized and placed in a l-liter flask with 700 cc. of water, and .after dissolution this solution is poured into an evaporating dish and heated. The mono-tungsten carbide is then sprinkled in small quantities into the solution and the solution containing the tungsten carbide is evaporated to dryness'with constant stirring. This procedure takes approximately twenty hours.

The powder isthen sieved through a 180 mesh sieve, loaded in nickel boats and reduced in an electric furnace in a hydrogen atmosphere in accordance' with the following schedule:

and the temperature then reaches about 600 0.,

' minutes.

which is maintained until reduction is complete. The boat is then pushed into a cooler with a reducing atmosphere and held there for fifteen As a fourth example of a manner of carrying out the present invention, from 1% to 10% of titanium carbide or vanadium carbide or chro-, mium carbide, or a combination of two of these materials or of. all three, may be combined with 60% to of tungsten carbide and 10% to 25% of tantalum carbide, these carbides being mixed to result in the production of an alloy containing 5% to 10% of cobalt or nickel or both.

As a fifth example of making this new alloy, 1

tungsten and carbon may be combined together in such proportions as to result in the production of a final alloy containing 84.2% of tungsten and 5.5% of carbon, suflicient amounts of a cobalt or nickel compound being added to assure that the i final alloy will contain about 10.3% cobalt or nickel or a combination of both. I

In combining the tungsten with-the carbon, the tungsten-and carbonmixture may be heated to a relatively high temperature, say up to 1200 C. in a reducing atmosphere containing hydrocarbon gases,,such as benzene, acetylene, and so forth, which hydrocarbon gases appear to aid the production of carbides which most readily enter into homogeneous combinations with cobalt, nickel and/or iron.

In the above examples, instead oi! using cobalt, nickel or iron-acetates in combination with the tungsten carbide, it is also possible to use the tartaric acid, or other organic acid salts of these metals. It is also possible to mix with the tungsten or other refractory metal carbides, some finely divided cobalt, nickel or iron-which has been previously reduced, and oftenthis mixture of finely divided, reduced cobalt, nickel or iron may replace part of the metal of the acetate or other soluble salt.

Some finely divided reduced cobalt, nickel or, in some cases, iron may be combined with the finely divided tungsten, tantalum, chromium, vanadium, or other refractory metal before the carburizing operation so that the carbidesv of the various metals in the final alloy are simultaneously produced. 7

Although both the high temperature treatments, namely the carburizing and the reduction, are carried out in reducing atmospheres it has been found most suitable to carry out the first operation in a hydrocarbon atmosphera while the second operation is carried out in a hydrogen atmosphere. The final sintering operation may also be carried out in a substantially reducing atmosphere, preferably of hydrogen.

Many other changes could be effected in the particular features of process treatment disclosed, and in specific details thereo1, without Substantially departing from the invention intended to be defined in,the claims, the specific description herein merely serving to illustrate certain ele-. ments by which, in'one embodiment, the spirit of the invention may be eflectuated.

What Iclaim is: 7 a a I 1. A process or preparing a hard metal alloy which comprises preparing a mixture including a tungstencarblde, mixing said carbide with an aqueous medium containing a concentrated dispersion of at least one water soluble, organir acid salt compound selected from the groupconsisting of the cobalt, nickel. and iron compounds .evaporating to dryness while continuously agitating, and heating the mixture in a reducing atmosphere. I

2. A process of making 'tungsten-cobalt-carbide combinations which comprises incorporating tungsten carbide with a'solution o1 cobalt'acetati 2,119,487 with agitation, evaporating to dryness while continuing theagitatlon, pulverizing and sifting the dried mass and then reducing the dried mass in I irom tungsten carbides which comprises forming i ly agitating, powdering and heating in a reducing atmosphere.

5. A process of producing a hard metal alloy which comprises heating finely divided tungsten with carbon in a hydrocarbon atmosphere, and

then mixing the finely divided product with a then heating the resultant mixture of tungsten carbide and cobalt acetate in a hydrogen atmosphere.

'1. A process of forming a hard metal alloy which comprises combining a finely divided tungsten carbide with a concentrated aqueous dispersion oil a soluble compound of a metal selected from the group consisting of nickel, cobalt and iron, with agitation, evaporating to dryness while continuing the agitation, pulverizing the dried mass, sitting the pulverized material and then reducing in hydrogen, p

s. A process of forming a hard metal alloy which comprises providing tungsten carbide, powdering the tungsten carbide, sprinkling the powdered tungsten carbide into a concentrated solution of cobalt acetate inproportions to give a final alloy containing between and 10.5% of cobalt, evaporating to dryness while continuously agitating, pulverizing the dried mass, reducing the powder by heating 'in a hydrogen atmosphere, pressing and forming the powder into desired shapes, and then sintering.

9. In the process of preparing hard metal alloys, the step of combining a tungsten carbide with a solution of a cobalt salt, which comprises sprinkling the carbide into a concentrated solution of the cobalt salt until the proper proportions are obtained and then evaporating to dryness while continuously agitating.

10. A'hard metal alloy comprising the reduction product of a tungsten carbide and a cobalt salt, particles of said carbide being encased in metallic cobalt and the encased particles being cemented together and being prepared by evaporating aslurry containing tungsten carbide and said salt to dryness, followed by pulverizing, pressing and sintering.

11. A hard metal alloy comprising a reduced mixture oi! tungsten carbide and cobalt acetate, particles of said carbide being encased in metallic cobalt andthe encased particles being cemented together and being prepared by evaporating a slurry containing tungsten carbide and said ble salt of the additional metal to form a slurry followed by reduction to dryness while contin tering.