US2441126A - Oxidation resistant alloys - Google Patents

Description

Patented May 11, 1948 Jacob Kurtz, Teaneck, N. Tungsten Corporation, poration of Delaware 1., assignor to Callite Union City, N. J., a cor- No Drawing. Application January 13, 1944, Serial No. 518,100

3 Claims. (CI. 7522) The present invention relates to alloys having a high resistance to oxidation and to the action of strong alkaline solvents such as fused alkaline nitrates. The alloy of the invention has particular advantages for use in making mounts for diamond dies.

Die mounts for hot drawing of wires must have a high resistance to oxidation. In drawing refractory metals, the drawing temperatures are frequently high enough to cause oxidation of the mounts at present in general use, to such a degree that the die will be loosened in the mount. Such a condition greatly impairs or even totally destroys the usefulness of the die, since the bearing in the die is no longer concentric in relation to the mount, nor is it any longer truly at right angles to the faces thereof. The axes of the bearings of the diamond nib and of the mount must coincide exactly. A high degree of accuracy in this respect is necessary and even a slight deviation from axial symmetry will greatly impair the usefulness and efiiciency of the die. Again, in the drawing of tungsten or molybdenum, it frequently happens that a piece of wire breaks in the die and must be dissolved out. For this purpose, a fused alkaline nitrate is generally used. Such powerful reactants, however, also tend to cause oxidation and even to dissolve the mount metals generally employed and consequently to loosen the die nib in the mount with the deleterious efi'ects hereinbefore described.

It is an object of the present invention to provide an alloy suitable for forming die mounts that will resist the oxidizing effects of temperatures encountered in hot drawing of refractory metal wires, such as tungsten or molybdenum wires and wires of other high melting point metals.

It is a further object to provide an alloy that will be suitable for use wherever it is necessary to prevent oxidation effects of high temperatures and of strong alkaline reactants.

Briefly described, the alloy of the invention consists of nickel, copper, chronium and silver :ombined in the proportions and according to the method hereinafter described. It must first be noted, however, that chromium, when heat ;reated either by fusion methods or by methods )f powder metallur y, has a marked tendency to ixidize and, in such case, not to alloy in a true :ense with the other constituents noted. On he contrary, the chromium oxide forms nodes ,nd these nodes are distributed through the mass If alloy of the other constituents in a porphyritic tructure. Such a result is highly undesirable.

According to the method of the present invention, the chromium is first alloyed with nickel to form a nickel chromium alloy. This is eiiected by adding 90% nickel powder to 10% chromium powder, both of about 200 mesh or finer. The

metal powders are thoroughly mixed as by ball milling until they are thoroughly commingled. The mixed nickel and chromium powders are then placed in a mold and compressed under hydraulic pressure of about 10 to 20 tons per square inch. The ingot so formed .is then sintered in a hydrogen atmosphere at a temperature of about 300-400 C. Great care must be taken to dry the hydrogen, as water vapor, which is present in nearly all commercially produced hydrogen, is a very active oxidizing agent and will cause the chromium to oxidize rapidly and to form the undesirable porphyritic structure above described instead of alloying with the nickel. The hydrogen may be dried by bubbling it through sulphuric acid or by passing it over phosphorus pentoxide.

The nickel and chromium may, however, be heat treated in any suitable non-oxidizing atmosphere other than hydrogen or the heating may be carried out in a vacum as in a high frequency vacuum furnace.

At the temperatures and under the non-oxidizing conditions mentioned, the nickel and chromium are sintered into a porous rod and are thoroughly difi'used so as to form an alloy having a high resistance to oxidation. This rod is then broken down to powder form by mechanical means such as crushing or hammering. I call this alloy metal A.

A second batch of metal nickel powder and copper powder 30% and also about 200 mesh or finer is thoroughly ball milled for several hours or until thorough distribution of the constituent powders is obtained. I call this metal, B metal.

A third batch of metal is then formed by mixing A and B metals in about the following proportions:

Percent 20% metal A 1 metal B 99 I refer to this metal as metal C.

The final alloy isthen formed by mixing from 75%-96% of powdered metal 0 with from 25%- 4% of silver powder.

Assuming that the proportions of metal C consist of 10% of metal A and of metal B, and assuming also that the final metal alloy is to consist of 90% of metal C and 10% silver, the

powders consisting of 1 niium; compressing resulting very satisfactory alloy will consist of the following:

Percent Nickel 64.8

Copper 24.3

Chromium .9

Silver e ,10.0i The proportions'giv'en are by'weighti In my Patent 2,374,942 issued May 1, 1945,,

filed contemporaneously with this application, I have described the use of this metaliforforming mounts for dies. The further treatment of the, powdered metal above for making die mounts or for 'other'purposes'; will" be the same. I'he powdered metal is first poured into a mold of the desired shapet andlcompressed powders with "compacting the same under hydraulic pressure describe'dj whether used" in a hydraulic press under a pressure M 20 tons pressure to the square inch. I

The pressed compact is removed from thepres's and givena presintering'treatment in a furnace in a dry hydrogen atmosphere at a temperature of from 300 to 400 C.'for*about one-half hour. Aiurther and'final 'sinterin'g is then eifected also in" a dryhyd'rogen atmosphere at a temperature of-from' about 800-900 C. for about a halfho'ur. Under this treatment thorough-diifusion and alloying of the'cons'tituents takes place without any trace of porphyritic characteristics andthemetal shrinks toabout'92%"to 80 of the volume of the compacted mass.

Instead of chr'omium, zirconium, beryllium or aluminum may be substituted in'= the same proportion as the chromium without substantial change either'in'tlie method or inthe characteristics of the finalalloy;

Chromium, zirconium, beryllium and aluminum' have-the same properties in adding resistance to oxidation when combined'with the other constituents of the alloy and should be alloyed separately with nickel in the same proportions as hereinabove stated for chromium alone to form the preliminary alloy. Thorough"diffusionlamd alloying of nickel with these metals should be elfected before adding to the other constituents if a true finalalloy is'to be obtained and a--p'or-' phy'ritic structure is to b'e'prevented'. In any case, however, the proportions given above for" the constituents are to b'e'observed, via? 75% to 96% ofm'etalC powder with from 25% to 4% of silver powder; The proportions ofthe constituents of the "final alloy will'then be within'the rangesof from'7'0'.2% t074%"nickel, 0.1% to 2.0% of one or more of 'thegroup consisting of chromium, zirconium, beryllium or aluminum, and from 29.7% to 24% copper alloyed with silver in the propor tions'of 75% to 96% of the 'combin'ed met'alsand 25% to'4'%* silver; orfrom 52.65% to"71.04% nickel, 0.075% to 1.92% chromium, zirconium, beryllium or'aluminum, 2'2-.'2'Z5% to 23.04% copperand' 25% to 4%" silver. 7

Having thus described my invention, what-I clainrisz' 1; Method of making analloy that comprises first mixing a batch of finely divided metal powders" consisting of 90% nickel and 10% chrothesame under hydraulic combining'from 1%-20% an'd'sh'eat treating the mass so compacted first at a temperature'or 300-400 C. and then raising saidternpera'ture to about 800-900 C. and maintaining thattemperature until all said constitu- "entmetals are thoroughly diffused, alloyed and sintered.

'2? Themethod of making an alloy of nickel, chromium, copper and silver that comprises first separatelyforming an alloy of"90% nickel and 10%. chromium, then combining with a batch consisting -3. The method of'm'aking'analloy of nickeL chromium, copper and silver that comprises alloy powder consisting of 90% nickel and-10%" chromium; with from 99%-80% said'com'bined powders tofrom 25 Number Name Date 1,519,862 Macy Dec. 16 1924" 2,075,444 Koehring Mar. 30, 1937" 2,192,744 Howe Mar. 5, 1940 2,205,611 Wasserman June 25 1940 2,289,897 B alke- July 1 4, 1942 2 ,331,909

' OTHER. REFERENCES Powder Metallurgy, by Wulff, publishedlay American Society for Metals, Cleveland, Ohio;-

1942. Pages 352-377.

from 1%-20%"- ofisaid' nickel chromium alloy inpow'der 'f'orni of '70 nickel'powder and': 30% copp'er'powder, and then adding from 75 96% of said combined metal powderssto fr'omfl hydraulic:

and alloying of the constituent of a nickel chromium of nick'el' and copper'powders in the proportionsofi% nickel and-30% copper; then adding from '75%-96'%*-of %-4% ofsilver powders; compacting'the same under hydraulic I-Iensel Oct} 19," 1943* Certificate of Correction Patent No. 2,441,126.

It is hereby certifi the printed specification of the above numbered patent requiring correction as follows: Column 2, lines 45 to 47 inclusive for 7 1 Percent I 20 0 meta A 1 1?20% meta A 80% metal B 99 read 9 95, 807 metal B and that the said Letters Patent should be read with this correc same may conform to the record of the eas tion therein that the e in the Patent Ofiice. Signed and sealed this 3rd day of August, A. D. 1948.

THOMAS F. MURPHY,

Assistant Uanwnzlm'mer of Patents.

Certificate of Correction Patent No. 2,441,126.

May 11, 1948. JACOB KURTZ r appears in the printed specification of the above 'on as follows: Column 2 1' mes 45 to 47 inclusive for 7 l A ercent "I A 20 0 meta 1 17-207 meta metal B 99 read 73-8073 metal B and that the said Letters Patent should be read with this correction therein that the same may conform to e record of the case m the Patent Office.

igned and sealed this 3rd day of August A THOMAS F. MURPHY,

Assistant Uanum'm'oner of Patenta.