US2048707A - Alloy - Google Patents

Description

Patented July 28, 1936 PATENT OFFICE ALLOY Carl Pfanstiehl, Highland Park, Ill., assignor to Pfanstiehl Chemical Company, Waukegan, 111., a corporation of Illinois No Drawing. Application November 15, 1934, Serial No. 753,220

13 Claims.

. This invention relates to a new alloy and more particularlyto an alloy having a cobalt matrix and containing carbides of tungsten and chromium.

Alloys such as -Stellite have heretofore been used in which chromium and tungsten carbides are imbedded in a cobalt matrix. If the per cent of carbon exceeds 2.75, however, such an alloy becomes brittle, particularly owing to the large size of the crystals of carbide formed.

It has now been discovered that an alloy having great value from the standpoint of corrosion resistance and toughness may be prepared fromchromium, cobalt, 'tungsten and carbon, with percentages of carbon above 2.75, providing the crystal structure is properly developed. At the same time alloys having less carbon than this may be improved in crystal structure.

It has further been discovered that a superior matrix may be produced by s'upersaturating cobalt with the carbides. e

In accordance with this invention a tough alloy of this type may be produced providing the metal is fused, and the fused metal is then frozen in an extremely short time. This period should be less than three seconds, and preferably is as low as one second, or even second. In order to accomplish proper cooling, it is preferred to subdivide the metal into small portions, preferably not greatly exceeding th inch indiameter when frozen.

A method of accomplishing rapid cooling is set forthin my co-pending application Serial No. 753,219, filed November 15, 1934.

A preferred range of proportions is as follows:

Parts Cobalt 35 to 50 Chromium 30 130 40 Tungsten 15 to Carbon As an example of the invention an alloy was prepared according to the following formula:

Cobalt 46.7 Chromium 30.8 Tungsten 19.2 Carbon 3.3

same time it is preferred that the materials be free from impurities as far as possible. In fluxing the alloy, pure tungsten, in dense form, for example in the form of tungsten rods or discs, such as pure wrought tungsten; pure dense cobalt, such as electrolytic cobalt in the form of little discs; pure dense chromium, such as is electrolytically deposited in small flakes or sheets, say .0l-.03 inch in thickness are employed. The carbon may be employed in pow 10 dered form, and it is preferred to use a pure carbon such as Acheson graphiteelectrodes.

These materials are mixed and heated and stirred in the absence of oxygen, and the resulting alloy is then rapidly cooled. I

It is preferred that freezing be accomplished in 3 seconds or less. This may be done by cooling in a chilled mold, with the alloy in the form of a slug less than A; inch in thickness. An ingot or slug fix x3 inches is satisfactory.

Improved results may be obtained by freezing the alloy even more rapidly. For this purpose the slug may be. broken up into granules, say to pass a mesh screen and to be caught on a 100 mesh screen, divided into small portions, fused and refrozen. The portions should be small enough to spheroid themselves by surface tension when molten, and preferably to form a spheroid of the order of th inch in diameter 'orless. When of this size, the globules will freeze readily in one second or less, under proper cooling conditions. a 1

. Somewhat more rapid freezing may be accomplished by welding the small spheroids to a pennlb, or other metallic base, since the cooling by contact with the metal of the nib speeds the cooling process somewhat. Apparently under these conditions freezing may be accomplished in about second.

At the same time if the spheroid is maintained in a molten'stage for 2 to 3 seconds, and is then frozen, a marked change occurs in the crystal structure of the alloy, the size of the crystals decreasing markedly. A preferred method of welding the spheroids to a base is set forth in my co-pending application Serial No. 706,565, filed January 13, 1934.

The change in the structure, under various cooling times is quite marked. A slowly cooled alloy shows large, generally dendritic crystals of carbides with segregated masses of matrix. The masses of matrix, however, appear to be crisscrossed by flne hair-like fibres. In this form the large crystals are readily visible to the naked eye.

When cast in a rod %th inches in diameter 55 the crystals become more broken up, and the areas of background more segregated. The crystals are still extremely large however and the large wide areas of carbides predominate in a 5 photomicrograph;

When cooled in a time of the order of 3 seconds, the crystal structure-has entirely changed and the masses of crystals have disappeared, and the alloy when etched and photomicrographed at 160 diameters shows a mass of small crystals, in-

terspersed with a few relatively large needle-like crystals, and with the matrix thoroughly dispersed. Many of the crystals appear to 'be hexagonalat this stage. Y When the alloy is cooled in a time of the order .of one second, for example, in a ball between .060 and .065 inches in diameter much more ma trix appears, and there is relatively less of the carbide, apparently due to supersaturation in solid solution in the matrix. The crystals of carbide are. long and fibrous, and their arrangement suggests a mass of matted asbestos. In some instances they will'arrange to resemble a herringbone weave in cloth, or even long spirals resembling shavings, Apparently the larger crystals are partially 'redissolved.

When a small spheroid is welded to a pen-nib,

40 ently due to the fact that the matrix contains much more carbides, which are in supersaturated solution therein. However the crystals are smaller and more segregated. The structure resembles greatly a picture of the Milky Way.

45 The ground or matrix is essentially pure cobalt, containing in it dissolved carbides. The carbides arerelatively insoluble therein, so that in alloys of this type very large proportions are segregated crystals of carbide. The crystal structure is not 50 only altered radically by differences in the cooling rate but at the same time the matrix is apparently supersaturated with carbides by a rapid cooling. more chemically resistant, particularly to corrosion such as is produced by ink.

This supersaturation is of value not only to the high carbon tungsten-chromium-cobalt alloys but also to alloys of the Stell'ite type.

The preferred alloy is of particular value for use in tipping pen-points. .It is hard, corrosion resistant, and tough.

The alloy is also valuable for use on steel nibs, which canbe readily tipped by the method of my co-pending application Serial No. 706,565. When so tipped the alloy blends with the pen-nib,

producing an alloy-enriched tip with no apparent sharp line of division from the nib. For example, a stainless steel, such as 18% chromium,

8% nickel is particularly suitable.

The welding of the alloy to pen-nibs or .other the alloy with a thin coating ofa metal readily alloying with the nib, and also alloying with the 75 a oy. 1 I

The result is that the matrix becomes alloy is substantially oxide free.

For example, when welding the alloy to a gold pen-nib, it is preferred to coat the spheroid with .001-.005 inches of gold. This gold may be readily applied by fusing gold and alloy together, the

gold being expelled to the outside of the spheroid 5 during the process. A coating may be applied by simply fusing the gold, but it is less desirable,

inasmuch as there appears to be an intermediate Cobalt 41 35. 8 49 25 Chromium 33 27. 7 Tlmasian 20 25 17. 5 5 Carbon 4 6. 2 5. 55

Some of the cobalt may be replaced by nickel, and various other metals suchas molybdenum and zirconium may be added as desired.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations shouldbe understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

What I claim as new, and desire-t0 secure by Letters Patent, is: v

1. An alloy having the approximate composition of cobalt 35 to 50 parts, chromium 30 to parts, tungsten 15 to 25 parts, and carbon 3 to 5 parts, said alloy having the internal structure 40 produced by heating alloy material inquantity to produce a spheroid by surface tension, to a temperature at which the material will fuse to form a spheroid by surface tension, and freezing the resulting spheroid from such temperature in a time of the order of one second or less. 2. An alloy having the approximate composition of cobalt 35 to parts, chromium 30 to 40 parts, tungsten 15 to 25 parts, andcarbon 3 to 5 parts, said alloy having the internal structure produced by heating alloy material in quantity to produce a spheroid of such composition of a diameter of the order of inch or less to atemperature at which'the material will form a spheroid by surface tension, and freezing the resulting spheroid from such temperature in a time of. the

order of one second or less.

3. An alloy as set forth in claim 1 in which the 4. A spheroid having a diameter of the order of inch or less composed of an alloy having the approximate composition of cobalt 35 to 50 parts, chromium 30 to 40 parts, tungsten 15 to 25 parts, and carbon 3 to 5 parts, said alloy having the internal structure produced by heating alloy material in quantity to produce a spheroid ofsaid diameter to a temperature at which the material will form a spheroid by surface tension, and freezing the resulting spheroid from such temperature in a time of the order of one second or less. objects may be aided by coating a spheroid of 5. A spheroid having a diameter'of the order of inch or less composed of analloy having the approximate composition of cobalt 35 to 50 parts,

11. chromium 30 to 40 parts, tungsten 15 to 25 parts,

and carbon 3 to 5 parts, said alloy having the internal structure produced by heating alloy material in quantity to produce a spheroid of said diameter to a temperature at which the material will 'form a spheroid by surface tension, and freezing the resulting spheroid from such temperature in a time of the order of one second or less, and said spheroid having on the surface thereof a thin, adherent gold coating, said gold coating having the adhering characteristics produced by fusing alloy and gold together, whereby the gold is substantially all expelled to the surface of the spheroid.

' 6. A spheroid as set forth in claim 5 in which the gold has a thickness of the order of .001 to .005 inch.

7. A pen nib having firmly welded thereto a tip comprising essentially an alloy having the approximate composition of cobalt 35 to 50 parts, chromium to 40 parts, tungsten 15 to 25 parts, and carbon 3 to 5 parts, said alloy having the internal structure produced by heating alloy material in quantity to produce a spheroid by surface tension, to a temperature at which the material will fuse to form a spheroid by surface tension, and freezing the resulting spheroid from such temperature in a time of the order of one second or less.

8. A pen nib as set forth in claim '7 in which the pen nib is gold.

9. A pen nib as set forth in claim 7 in which the pen nib is steel.

10. An alloy as set forth in claim 1 in which the alloy has the approximate composition of cobalt 41, chromium 35, tungsten 20 and carbon dparts. I

11. An alloy as set forth in claim 1 in which the alloy has the approximate composition of cobalt 46.7, chromium 30.8, tungsten 19.2, and carbon 3.3 parts.

12. A spheroid as set forth in claim 5 in which 15 the gold is 14-18 K.

13. A spheroid of an alloy having the approximate composition of cobalt to 50 parts, chromium 30 to 40 parts, tungsten 15 to 25 parts, and 20