US2470034A - Electric contact formed of a ruthenium composition - Google Patents

Description

Patenteci May 10, 1949 ELECTRIC CONTACT FORMED OF A RUTHENIUM COMPOSITION Franz R. Hensel, James W. Wiggs, and Vernon E.

Heil, Indianapolis, Ind., assignors to P. R. Mallory 85 (30., Inc., Indianapolis, Ind., a corporation of Delaware No Drawing. Application November 27, 1945, Serial No. 631,206

4 Claims.

This invention relates to ruthenium metal compositions.

An oliject of the invention is to improve ruthenium compositions.

Another object is to improve electric contacts and the compositions thereof.

Other objects of the invention will be apparent from the description and claims.

This invention is a continuation-in-part of our prior-filed co-pending application, Serial Number 474,178, filed January 30, 1943, now abancloned.

The invention contemplates a sintered metal composition formed essentially of ruthenium, cohalt and gold.

The advantages of this composition over cobaltfree materials are its increased density, wear resistance and particularly its increased resistance towards arcing.

The advantage of such a composition as compared with silver base materials is resistance to sulficling.

Gold is a material which is most resistant to sulfiding. It has, however, definite disadvantages as a contact material as compared with silver, such as needle-type transfer characteristics and Welding at low current ratings.

These disadvantages are overcome by combining the gold with ruthenium and cementing the ruthenium with the gold by the addition of cobalt which enters into a solid solution formation both with the gold and the ruthenium.

The gold-cobalt alloy has a liquid phase at approximately 1000 C. This liquid phase combines with the ruthenium dissolving a small portion of the latter, thereby causing the sintered compacts to shrink. Thus a practically 100% dense structure is formed which is highly resistant to arcing when used in electrical devices for contacts or the like.

The oxidation characteristics of both ruthenium and cobalt are such that oxide layers are formed, eliminating any sticking tendencies of the contact materials without creating films of Per cent by weight Ruthenium 60 to 95 Cobalt .5 to 20 Gold, balance.

Some of the specific compositions which can be readily produced and which have suitable properties for such applications as electric con tacts, for example, are:

Per cent by weight Ruthenium 80 Cobalt 5 Gold 15 Per cent by weight Ruthenium Cobalt 10 Gold 25 Per cent by weight Ruthenium 92 Cobalt 3 Gold 5 Per cent by weight Ruthenium Cobalt 8 Gold 17 The metal compositions are produced by powder metallurgical methods which comprise mixing the powders by such methods as ball milling, pressing the mixed powders into suitable shapes at unit pressures varying from about 5 to 50 tons tons per square inch and sintering in a non-oxidizin atmosphere over a temperature range of about 1000 C. to 1500 C.

The procedure may be modified by uniting first the ruthenium and cobalt powders in such a manner that the ruthenium particles are coated with cobalt. The mixture is pressed and then sintered at temperatures ranging from about 1100 C. to 1400 C. depending on the amount of porosity desired in the sintered compact. The porous compact is then alloyed or impregnated with gold at temperatures ranging from about 1200 C, to 1400 C.

The metal compositions may be pressed in the form of small discs, slabs, bars, rods or other forms for use as electric contacts, or they may be formed into special shapes for use as contacts or other purposes.

Contacts of this material have proven suitable for D. C. voltage regulator contacts.

One contact combination which has been found very good for D. C. operation comprises a positive contact of the ruthenium-cobalt-gold metal composition and a negative contact of tungsten. Other contact combinations which suggest themselves are those wherein the positive contact is one of the metal compositions of the present invention and the negative contact is of tungsten, tungsten carbide or a refractory metal composition such as tungsten or molybdenum or compounds of these metals such as carbides, borides or nitrides mixed or impregnated with metals or alloys of the copper, silver, gold group.

The metal compositions of the present invention give satisfactory performance as contact material when operated against themselves both in A. C. and D. C. applications. While in certain D. C. applications it may be preferred to use them on the positive contact, tests have indicated that they perform satisfactorily on the negative contact.

The metal compositions of the present invention have also shown satisfactory performance when used in contact combinations where the mating contact consists of platinum-iridium, platinum-ruthenium, platinum-osmium-iridium, platinum-palladium, pure palladium, pure ruthenium, osmium-rhodium and similar alloys.

The new metal compositions can also be used in contact combinations where the mating contact consists of coin silver or sterling silver or silver alloys generally useclfor contact work.

Small percentages of such metals as nickel, iron, silver, copper, palladium and platinum group metals, tungsten, molybdenum may be present in the final composition providing they do not deleteriously affect the contact properties of the ruthenium-cobalt-gold combination.

While specific embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed, is:

1. An electric contact formed of a metal composition consisting of to 95% by weight of ruthenium, .5 to 20% by weight of cobalt, and the balance all gold.

2. An electric contact formed of a metal composition consisting of about by weight of ruthenium, about 10% by weight of cobalt and about 25 by weight of gold.

3. An electric contact formed of a metal composition consisting of about 92% by weight of ruthenium, about 3% by weight of cobalt and about 5% by weight of gold.

4. An electric contact formed of a metal composition consisting of about by weight of ruthenium, about 8% by weight of cobalt and about 1'? by weight of gold.

. FRANZ R. HENSEL.

JAMES W. WIGGS. VERNON E.

REFERENCES CITED The following references are of record in the file of this patent:

UlilI'IED STATES PATENTS 1-lu7:r.=ber Name Date 1,165,448 Richter Dec. 28, 1915 1,415,233 Fahrenwald May 9, 1922 1,832,307 Kingsbury Nov. 17, 1931 2,048,647 Feussner et a1 July 21, 1936