US1924384A - Tough tungsten carbide alloy - Google Patents

Description

I Patented Aug. 29, 1933 PATENT OFFICE 'rouea' TUNGSTEN CARBIDE ALLOY Winston F. Stoody, Whittier, Calif., assignor to Stoody Company, Whittier, Calif., a corporation of California No Drawing. Application March 2, 1932 Serial No. 596,410

4 Claims.

This invention relates to an improved alloy of extreme hardness.

An object of the invention is to provide an improved alloy consisting principally of tungsten carbide and which is advantageous in that it has virtuallythe hardness of pure tungsten carbide and at the same time is considerably tougher than pure, or substantially pure, tungsten carbide. Pure, or substantially pure, tungsten carbide while extremely hard is very brittle. It frequently has quite a number of shrinkage cracks produced on changing from liquid to solid in its production. While it is extremely hard and highly resistant to abrasion, because of its brittleness and the presence of shrinkage cracks it cannot withstand percussion to any great extent nor will it withstand bending moments. Heretofore it has been proposed to alloy tungsten carbide with nickel, the nickel content running from 2 percent to 18 percent. Sometimes the nickel was the sole substance added and m other instances additional metallic elements or combinations have been added. When nickel is used alone to alloy with the tungsten carbide in greater amounts than 5 percent it does not seem to'materially toughen the resulting product and the hardness is greatly decreased.

It hasalso been proposed heretofore to alloy tungsten carbide with copper, however, experiments in this direction insofar as I am aware have resulted in the copper having .the tendency to segregate and to occur in the alloy only in localized sections. Because of this lack of uniformity such an alloy cannot be used successfully.

Specifically'an object of the present invention is to-provide a new alloy consisting principally of tungsten carbide alloyed with copper and nickel, giving a resulting product which is of uniform character, a very fine grained structure, having a hardness which is almost as hard as pure tungsten carbide, and having extreme toughness as compared with that of pure tungsten carbide, enabling the alloy to withstand percussion and bending moments.

Specific manners in which I prepare the improved alloy may be described as follows. My preferred alloy consists principally of tungsten carbide with about 5 per cent nickel and-2 percent copper. The impurities present should not exceed 1 percent except that iron may exceed 1 percent and may run as high as several percent due to the fact that it is almost impossible to obtain commercial tungsten, copper and nickel, free from iron. The quantity of nickel in the alloy, while being preferably about 5 percent, may vary between 2 per cent and 18 percent. The copper content may vary likewise from 2 percent to 18 percent. To manufacture the alloy, pure tungsten powder may be mixed with 5 percent by weight of nickel and 2 percent by weight of copper and the entire mixture may be placed in a carbon crucible. The crucible is then placed between the terminals of an electric discharge the voltage and amperage of which is so proportioned that the flow of current through the carbon crucible is sufiicient and so regulated as to raise the temperature of the crucible to the melting point of the entire mix. When the contents of the crucible have become molten the current is left on and the mix is left in a molten condition a short period of time, which may be about one minute or until it appears that the mix has absorbed suflicient carbon from the walls of the crucible to unite with the tungsten to form a tungsten carbide. The alloy thus produced can be allowed to cool in the crucible and the crucible subsequently broken to recover it or it may be poured from the crucible into suitable molds.

It is not essential that pure tungsten powder be used and in some instances the alloy may be produced by remelting previously formed tungsten carbide with the added weight of nickel and copper. In other instances the mix may be part of previously formed tungsten carbide and part pure tungsten powder. When tungsten carbide is used in the mix instead of tungsten powder I find that not quite so much heat is required and it is unnecessary to keep-the heat on for any longer time than that required to melt the mix.

The new alloy produced has a hardness nearly the same as that of pure tungsten carbide. It is capable of scratching corundum, which is 9 on Mohs scale. At the same time while its hardness is retained the alloy does not have the brittleness of pure tungsten carbide and instead is quite tough .and strong.

In the preferred alloy it will be noted that the nickel content exceeds the copper. This is not essential as I have obtained some very good results by using 5 percent copper and 2 percent nickel. A difliculty, however, is encountered in the smelting when the copper exceeds the nickel materially. Apparently the presence of the copper causes some kind of an intensive chemical reaction under the high temperature. While this is purely surmise, I do note that during the overflow during smelting.

smeltingthe high quantity of copper causes considerable blowing and has the tendency to blow the smelted metal in the crucible causing it to An alloy produced, however, with 5 percent copper and 2 percent nickel has more of a silvery appearance and is advantageous in that it will run into an intricate mold much better than in the instance where the nickel is higher than the copper. The grain structure of the alloy where the copper exceeds the nickel materially is also changed.

I have found that the blowing during the smelting where the copper materially exceeds the nickel can be corrected largely by using Monel metal. Monel metal consists chiefly of 68 percent nickel, 27 percent copper, and 5 percent iron. I find that by using Monel metal and copper that I can materially increase the proportion of copper to nickel in the resulting product without causing the molten metal to blow to such an extent that it causes difiiculty in handling.

I have. determined also that it is possible to produce quite a satisfactory alloy by using Monel metal alone in conjunction with the tungsten carbide. In such instances I prefer to use from 7 percent to 10 percent Monel metal and the balance tungsten carbide. Considerable success, however, has been obtained using Monel metal in percentages from 2 to 20 percent. I find when using Monel metal instead of nickel and copper that the hardness and toughness of the resulting product is effected in direct proportion to the amount added. As an illustration, 2 /2 percent Monel metal makes the resulting product slightly tougher than pure tungsten carbide and for all practical purposes the alloy is virtually as hard as pure tungsten carbide.

When the Monel metal content is increased, however, to 20 percent I find that the resulting product although sufiiciently hard to be used as a lathe tool is yet extremely tough and cannot be easily broken.

Although my improved alloy is a smelted product it does not appear to be a true chemical compound. The physical characteristics of the resulting product considered along with its grain structure indicate that it is a composite metal similar to a sintered tungsten carbide product. The physical characteristics lead me to surmise that when using copper and nickel that these two elements alloy together to make a compound or alloy similar to Monel metal and that this 8 alloy in turn acts as acement or hinder holding together the tungsten carbide particles. This theory, however, is purely surmise on my part and is not asserted with any great assurance that it is correct. It is possiblev that the nickelv in combination with the copper may possibly make the alloy a compound of tungsten, carbon, copper and nickel and, if this is the case, the nickel very likely acts somewhat as a catalytic agent inducing the copper to combine with the other 0 elements present. The improved method of making the alloy enables a very high content of copper and nickel to be introduced and it is possible that the combined copper and nickel may run as high as 25 percent with the balance tungsten carbide. The resulting product is extremely tough and is inherently hard in that it may be used for different purposes, such as lathe tools, without any kind of heat treatment. By changing the proportions of copper and nickel, that is by using less of either or less of the combination, I can produce an alloy haying practically any desired characteristic in an inherently hard, abrasive resisting, refractory alloy.

Various changes may be made in the details of production of the improved alloy as fall within the scope of the appended claims.

I claim:

1. A cast alloy consisting of 2 /2 to 18 percent nickel, 2 /2 to 18 percent copper, and the balance virtually all tungsten carbide.

2. A cast alloy consisting of 2 A; to 18 percent nickel, 2 to 18' percent copper, and the balance virtually all tungsten and sufficient carbon to convert all the tungsten into tungsten carbide.

3. A cast alloy consisting of 90 percent or over of tungsten carbide and the balance principall Monel metal.

4. A cast alloy consisting of about 5 percent 120 nickel, 2 percent copper, and the balance being virtually all tungsten carbide.

WINSTON F. STOQDY.