US2126745A - Alloy - Google Patents

Description

Patented Aug. 16, 1938 YUNirEo STATES PATENT OFFICE Annoy Anthony G,'de Golyer, New York, N. Y.

- No Drawing. Appllcation August 25, 1936,

Serial No. 97,815 i 3 Claims. (Cl. 148 32) cuttingtools, the cutting eiliciency of which is 10' superior to that of present known high speed steels and other alloys. A further object is to provide an alloy which is free from, or substantially free from carbon and which is readily, amenable to thermal treatment, by means of I 16 which the hardness, tensile strength, cutting efficiency and other physical properties and characteris'tics may be accurately controlled over a comparatively wide range.

I have found through experiment that by al- 20 loying or otherwise intimately combining boron,- tungsten; vanadium, chromium, zirconium and cobalt within the range of boron 0.50% to 3%,

tungsten 5% to 30%, vanadium 1% to 8%, zir-' hardness, resistance to impact and certain other important physical properties can be developed only through thermal treatment, or through me 35 chanical working and subsequent thermal treatment. Bodies of the alloys which have been subsensitive to various operating conditions as to greatly restrict the'scope of usefulness. One of the greatest disadvantages of such heretofore proposed compositions is that none of them are responsive to thermal treatment for regulation of physical properties, and consequently physical properties and characteristicsare governed entirely by the chemical composition of the sintered or cast material. I

My alloy may be used in the asvcast condition, 10

or it may be forged or otherwise mechanically worked. In either case I prefer to subject the, alloy to thermal treatment before using it as a cutting tool or die. Both the cast .and forged material are equally amenable to thermal treatment. For example, cast bodies of this alloy may have a hardness of from 50 to 60 on the Rockwell C. scale and by subjecting the material. to suitable thermal treatment, such as quenching from a temperature higher than approximately 1,000 C., the hardness may be lowered to anapproximate range of from 40 to 47 Rockwell C. In this condition the bodies may be ground, shaped or formed) as desired. The alloy may subsequently be submitted to a second thermal treatment, such as heating to a temperature of less than 1,000 C. for a period of one hour or more, by which the hardness may be increased to from approximately 60 to 70 Rockwell C. In the latter condition the alloy is especially valuable for the cutting or mechanical working of a large number of metals and alloys, as well as numerous non-metallic materials. An important property of this alloy is that virtually all -of the maximum hardness, developed by thermaltreat- 5,

J ment, is retained when the alloy is subjected to I .jected to such treatment are particularly valu-J elevated temperatures. s. uch as are generthan such steel," all of them have disadvantages which render them unsuitable for general application asmetal 'cutting or forming tools. Compositions containing principally carbides of tungsten, molybdenum or tantalum bonded with a v relatively soft matrix metal have a high degree of hardness, but are extremely brittle. Cast compositions of the types heretofore proposed require the presence of at least 1.50% carbon to qualify as metal cutting tools and, as is' well known, such alloys are not only brittle, butare so ated in the tip of a tool cuttingmetal at .high speed. Although the alloy has a high degree of hardness and resistance to abraslon by hot metal; 40 chips, especially after thermal treatment, it is remarkablyresistant to failurefrom sudden or repeated shock. "Therefore, tools made of the present alloy retain an efficient cutting edge for I longer periods than other tools. I 5

,The more important distinctive and valuable advantages are, apparently, due to the presence of appreciable amounts of .boron in-the compo-- sition, in conjunction with the other essential component elements within the percentagesspec ified herein,

I have. found that molybdenum may .beused to supplant all or a portion of the tungsten of the present alloy. Likewise, uranium may be used in place of either tungsten or molybdenum.

Specific examples of compositions within the scope of the present invention which I have found well adapted for metal cutting tools, dies and the like are the following: boron 1.20%, tungsten 14%, vanadium 2.75%, chromium 5%, zirconium 1.45%, cobalt balance; boron 2.10%, tungsten 19.50%, vanadium 4%, chromium 4%, zirconium 0.80%, cobalt balance; boron 1.65%, molybdenum 13%, vanadium 3.50%, chromium 3.5%, zirco-' nium 3.75%, cobalt balance; boron 1.70%, tungsten 5%, molybdenum 10%, vanadium 5%, chromium 8%, zirconium 4.6%, cobalt balance; boron 1.10%, molybdenum 12%, vanadium 6%, chromium 7%, zirconium 1.75%, cobalt balance.

An objective of the present invention is to provide alloys having high hardness, high resistance to shock and impact, advantageous metal cutting properties, etc., which are free or substantially free from carbon, and thus eliminate all of the serious disadvantages associated with carbon containing non-ferrous alloys or compositions intended for metal cutting tools. Although I prefer to have the alloys of this invention entirely free from carbon, in many instances I have found carbon present in the nature of an impurity incidental to manufacture. It is important to restrict the amount of carbon so present to a maximum of about 0.15%, as I have found that the presence of higher percentages of this element make the alloy extremely brittle and subject to failure during cutting operations, and, greatly retards or entirely prevents the desired and necessary reactions during thermal treatment. Furthermore, the presence of appreciable amounts of carbon decreases the red hardness of the alloy, i. e. hardness at temperatures of approximately 550 C. and higher.

By reason of the fact that the elements forming the essential components of the alloy of the present invention invariably are contaminated with other elements when produced in commercial quantities, the alloys of my invention usually contain insignificant amounts of one or more elements in the nature of impurities incidental to manufacture. Because of the fact that the maximum values of physical properties of the present alloy can be developed only through thermal treatment, it is essential that the amount of such incidental impurities present be limited to percentages which will not be'efiective in retarding,

or entirely preventing the necessary physical reactions during thermal treatment. Further, the

percentages of such impurities should also be restricted to amounts which will not be effective on the physical properties or characteristics of the alloy either before or after thermal treatment.

I have found that the most harmful impurities commonly present, in addition to carbon, are silicon and aluminum. The presence of either of these elements in amounts greater than approximately 1% renders the alloy of the present invention entirely unsuitable for thermal treatment by means of. which the hardness, tensile strength and with one or more of the essential components of the present'alloy, and such compounds are not only hard, brittle and lacking in impact resistance, but are virtually insoluble in the solid composition during thermal treatment. It will be apparent, therefore, that the presence of effective amounts of impurities, such as carbon, silicon and aluminum, materially change the character of the alloy through rendering it not amenable to thermal treatment.

My investigations indicate that the preferred structure of a body of the present alloy is produced only by means of thermal treatment, and that this comprises at least two principal constituents: one, a relatively hard intermetallic compound of boron with one or more of the other essential components; and, second, a solid solution of two or more of the essential components which has a lower degree of hardness and functions as a matrix. In some instances the structure will contain a third constituent in the nature of an eutectoid. The ratio of the constituents and the ratio of particle size in any particular body of the alloy may be accurately controlled and fixed over a wide range by means of thermal treatment, or mechanical working and subsequent thermal treatment.

By reason of the combined advantageous physical properties possessed by the alloy of the present invention, tools and other articles composed of this alloy may be operated efliciently and economically under conditions which are impossible or unecoriomical with tools or articles composed of heretofore known alloys or metallic compositions.

By the term the balance substantially cobalt in the foregoing and in the following claims, I intend that the alloy of, the present invention comprises boron, vanadium, zirconium, chromium and metal of the group tungsten, molybdenum and uranium, within the percentage limits specified, with the remainder cobalt except for ineffective amounts of impurities which may be present incidental to manufacture, as hereinbefore explained.

I claim: x

1. A precipitation hardened alloy containing boron 0.50% to 3%, metal from the group tungsten, molybdenum and uranium 5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%, chromium 1% to 25%, the balance cobalt.

- 2. A precipitation hardened alloy containing boron 0.50% to 3%, tungsten 5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%, chromium 1 to 25% the balance cobalt.

3. A precipitation hardened alloy containing boron 0.50% to 3%, molybdenum 5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%,

. chromium 1% to 25%, the balance cobalt.

ANTHONY G. DE GOLYER.