US2253476A - Metal alloys and method of making composite alloys of definite compositions therefrom - Google Patents

Description

I Patented Aug 19, 1941 METAL ALLOYS AND METHOD OF MAKING COMPOSITE ALLOYS F DEFINITE COM- 7 POSITIONS THEREFROM Roy T. Wirth, East Cleveland, Ohio No Drawing.

Original application July 20, 1936,

Serial No. 91,621. Divided and this application July 18, 1938, Serial No. 219,881

' 22 Claims.

The present invention relates to a novel process of making extremely hard carbide containing alloys of definite composition which are particularly adapted for use in the manufacture of high speed cutting tools or implements subject to abrasion, although such alloys may be used for various other purposes. In addition, the present invention discloses several specific alloys which give excellent results when made according to the present process.

The present invention is a division of application Serial No. 91,621 filed July 20, 1936.,

An object of the. present invention is to provide a novel process for the production of carbide containing alloys having suitable hardness, tough- I ness and red hardness to enable tools made therefrom to out other metals at highspeed.

Further objects and advantages of the present invention will be apparent to those skilled in the art, from the following description thereof which sets forth in detail combinations of ingredients embodying my invention, which combination of ingredients constitute several of the various forms in which the process of the invention may be used.

The process of the present invention involves I the production of a casting mixturecomprising a matrix metal and a preformed hard component, such asv a carbide or carbide alloy. The pre-' formed hard component is 'preferably mixed with ,a fused bath of matrix forming metal, that is, the' carbide or carbide alloy-infthe form of small particles or powder, or pressed slugs thereof-is mixed with the fused matrix forming bath which is then cooled, as by casting, to obtain the carbide carried in a matrix material. It should' benoted that carbide must be retained in the cast composition, that is, the carbide is not melted as is-the usual procedure. Therefore, the carbide is sintered, that is the carbide is hea d and cooled in associationwith the molten be. h, not melted. The cast compositions are there ore novel in that they contain a sintered hard constituent such as a sintered carbide or sintered carbide alloy. The cast compositions are not 1 only harder but considerably tougher than alloys made in the usual manner, such properties are probably due to the fact that the carbide has been retained in a sintered condition. Y

The process may comprise mixing particles of a hard component with a molten bath and casting to obtain a body of approximately the desired size and shape, such as a cutting tool, containing thesintered hard constituent. For example, particles of a carbide of metal. of the chromium group may be mixed with a molten bath of one or more metals of the iron group,

.preferably cobalt, and then cast in association with the molten constituent to obtain a cutting tool or :body of approximately the'desired size and shape containing sintered carbide of metal of the chromium group. In this case, for best results, the percentage of say tungsten carbide of the formula WC should be about 40% .or more,

usually not more than about 65%.

An added feature-of such compositions co taining: sintered components, as compared with other hard compositions, is that they respond to heat treatment if properly made, that is, the hardness may be varied by further subjecting the cast or'cooled composition to a temperature below' the'melting point of the composition, the

temperature varying according to the hardness andother properties desired, and being preferably between 1100 F. and a temperature just below the'rnelting point of the composition. There sition containing the sintered hard constituent is heated for a suflicient length of time at a ternperature near the melting point, the hardness s0 produced is a permanent hardness and'thecom position cannot be returned to a condition such as existed before such heat treatment. v

Compositions of greater hardness are obtained where the hard component is sintered in association with a molten bath containing not only metal of the iron group but also the metal or metalsof the hard component. For example, if it is desired to make a cast composition contain- '1 ing sintered tungsten carbide, having the formula prise at least 30% to 35% of themolten bath,

although it may be considerably higher, or about of the molten bath. The molten bath may also contain some carbon, but thecarbon should not be present to the extent that the matrix ma terial would be of insufllcient strength or possess undesirable properties. Where the carbide is sintered in association with such a molten alloy bath, the percentage of sintered carbide maybe somewhat lower than in the case oi. only iron group metal and may be as low as about 20% to 25%. The fact that the molten bath contains the metal of the carbide in sufilcient quantity makes the sintered condition of the carbide more easily attained.

Compositions containing chromium, carbon and tungsten, chromium, carbon and molybdenum, or chromium, carbon and both tungsten and molybdenum have been found particularly adapted as hard components, although they are useful in themselves for some purposes. The following analyses give typical examples of such alloys.

Tungsten and/or molybdenum. 6

cobalt, etc, and impurities Chromium Carbon mum amount of carbon which can be dissolved in .5

and/or combined with tungsten without forming graphite is less than the amount of carbon which can be dissolved in and/or combined with chromium without forming graphite.

In making 'such alloys, particularly where high carbon contents are employed, it is preferable to use the elements in the powdered form, and to mix them together in the desired proportions and then to press slugs oi the mixed powders, a suitable binding material being added to hold the powders in shape, it desired. The pressed slugs are then heated to an elevated temperature or sintered to form the hard component. The alloys may also be made by using the metallic carbides, such as exist in the final alloys, in powdered form. Where this is done, the carbides are formed separately, powdered to suitable fineness, mechanically mixed by themselves or with chromium, tungsten, carbon or powdered alloys thereof, and then heated or sintered to form the final alloy.

In alloys of the present type, it is to be understood, of course, that the usual impurities are present; that is, that there may be small quantities of other mteals such as iron, or the like, and also that special elements such as titanium, zirconium, tantalum, and the like, may be added in small quantities to give special properties to the alloys, and that where such special elements are added they are in such small quantities that the main alloy is always substantially a carbide composition containing chromium, carbon and one or more of the other metals of the chromium group. Cobalt, or one or more of the metals of the iron group may be present up to 10 percent, but where present, must be held low enough not to afiect the carbide formation of the alloy. These alloys, which are essentially carbide alloys, that is, the alloy is essentially composed of carbides of the metals present, are particularly adapted for tion, it has been found that where a carbide or Hard component Matrix component Carbon asao Chromium 24-28 Chromium"..- 55.0-80.00 Tungsten- 12-18 Tungsten and Cobalt 64-54 v impurities 32.0-38.00 Carbide Low carbide alloy is' mixed and sintered in association with a second molten alloy, that excellent results are obtained where the second alloy contains the metal or metals of the carbide or carbide alloy, as well as metals of a difi'erent group. If a straight metallic carbide is used, such as either chromium or tungsten carbide, it may advantageously be used with a molten alloy containing the metal of the carbide and another metal.

Thus the above described aalloys or hard components are preferably mixed and sintered with matrixiorming alloys which should contain the metal or metals oi the essential carbide or carbides oi the hard component together with a metal or metals of another group, preferably metals of the iron group such as cobalt. The matrix iorming alloy may contain carbon as well,

but preferably an insufilcient amount of carbon to have a particularly high carbide content. The following examples are given:

Composition limits of final alloy impurities-- Balance Final alloy limits of composition Carbon 1 7 Chromium l 15 Cobalt Not less than 5% Tungsten Not less than 38% The preformed hard component, of the above examples, is mixed-4n the form of small particles or powder-with a molten bath of the matrix alloy, the hard component being sintered in association with the molten matrix material so as to produce on cooling, as by casting. rticles or the hard component-carried in a matrix material. The particles or powder of the preformed hard component may be pressed in compact forms, such as slugs, before being mixed with the molten bath. Since it is not desirable to compress the powder or particles too strongly, but at the same time have a material which can be readily handled, a temporary binder such as an organic binder may be used to strengthen the pressed bodies.

The sintered hard component will ordinarily, be from about 20% to about 65% oi the entire composition, although a lower limit might be used when casting bodies of small cross-section. However, when the process is used to provide a composition suitable for use with the process described in my application Serial No. 405,540, filed November 7, 1929, the hard component may be present in even greater quantity. In this case, a composition is prepared according to the present process and the composition thus prepared in a matrix material, powdering such material is powdered, pressed and sintered to form a rigid and pressing and sintering the powder to a rigid body of any desired size and shape. 7 body.

The above hard and matrix components may 4. The process of making a non-ferrous cobalt 1 also be preformed separately, each powderedto p mm Q D I K ix lm f l f 8 suitable fineness, the powder mixed in desired preformed hard carbide of metal of thelchromium proportions, and the powder mixture may then group with ,a non-ferrousmolten batmcontain- Y be pressed and sintered to a rigid body of deing cobalt and containin -chromium and tung- 4 sizeand shape. v sten, retaining preformed particles of the hard 'Where a matrix alloy, in the solidified concompositi n in aisintered condltloninthelnolten. 'dition, contains of itself a considerable amount bath d ca tin the mixture.

* "of carbide best results appear to. be obtained by I The Process, m a cast -m sintering therewith acarbide or carbide alloy cobalt P w s 19171111131 containing the same elements the same mixture of retained particles of a preformed hard wide, are present in the a of the tr metal carbide in a sintered conditionin associamom t tion with a non-ferrous molten-batbcontaining The following example is s ven: c lt. and casting said mixture.

i I 6. The process, of making a cast non-ferrous Hard compoPnent Matr complgnnt t domposite composition 0 H g forming a er 5;; Chi i $3 0 substantially uniform casting .niixture by'mixing C rgmmm C g particles of a preformed hardcomposition comag inggg z -f'g 'a posed of a hard metal and a metalloid with a v 7 1m impurities 43.19 impurities 41.6 n ferrous molten bath containing cobalt and retaining particles of the preformed hard com; The above components may be mixed and the Position i int ed condition in association hard component sintered in association with a i h h m l en bath. and castin ,th'e lnixture. molten'bath of the matrix component. However, 7. The step in the pro e 0! ng a non-i as an object of the process'is to obtain the carferrous comp comprising. casting amixhide in a sintered condition thus obtaining an o u n metal- -111 8 improvement in the strength and hardness or- 30 lt. and "ret ined. sintered. p ic s o p e-. 1 the final alloy, the results obtained, using a formed u sten carbide.

-matrix material which alIeady contains a rather 1 -T step n the P ocess of makingia non- 7 high percentage of carbide, are inferior to the. ferrous cobalt composition comprisin castingsforegoing examples, The'process, however, promixture of retained sintered particles of a prevides a means of inreasing the hardness of such formed hard metal component, containing '8- a matrix j ent m a beneficial manner, metalloid, and non-ferrous molten metal, con- Other modes of applying the principle of my taining cobalt and metal'of the hard component. invention may be employed instead of the one 9. The step-in the pr ofmakins a nonexplained, change being made as regards the ferrous cobalt composition compri i f rming e 3 process herein disclosed'o'r the materials em- 40 castinamixture Of 'letamed t r P i l ployed in carrying out the process, provided the of a pr for metal mp nent. c nt lnsteps or step stated by any of the following 8 a l r n s i n wi h 8- n n ll claims'or the equivalent of such stated step or non-ferrous u ti 8 tool allay. c in b t. I steps be emp1yed chromium and tungsten. I v I 1, therefore particularly point out and dis- A- a n rr mp i ion comp tinctly-clailn as'my invention: substantially]bf' carbon chromium; cobalt and 1. The process of making a non-ferrous cobalt tungsten;:" said'.g=jcompos tion comprising a cast composition comprising mixing particles of a mixture-of'a molten non-ferrous-cutting toolalloy preformed hard metal carbide with a non-ferrous. composed substantially of ilhromiuin, tungsten molten bath containing cobalt and containing and cobalt,', and;.retained sinteredparticles of av themetal of the carbide, retaining particles of preformed carbide. of metal of the chromium the preformed carbide in a sintered condition group. I p a in association with such molten bath'and castlief-A cast non-ferrous composition composed ing such mixture to obtain sintered particles of. substantially of carbon, chromium, cobalt and g I preformed carbide carried in a matrix material. '65. tungsten, andcontaining 3.5%"toj9.0%- carbon,

- 2. The process of making a non-ferrous cobalt 38.0% to 58.0%"chrbmiilni', and 33.0%. to 8.5% i composition comprising mixing particles of ,pre-' cobalt and tungsten. the .cobalt' being at least formed hard metal carbide with a non-ferrous 5.0% and the tungsten ,lnot less than 15 091,; molten bath containing cobalt and containingthe said composition comprising a .castixtu r metal of the carbide, retaining particles of the so lt non-ferrous ttm m1 alloy composed preformed carbide in a sintered condition in assubstantially f ch romjum,' tungsten and t, 'sociation with such molten bath, casting 'such: I and contaimng chromium 249% t 2 9%, mixture to obtain sintered retained particles of tungsten 123% 183% ,amlv cbbalt 643% t preformed carbide carried in a matrix material 543%,1and retained-fighter particles of and thereafter h ating between 1100 F. and a'iili ai Hard combonent composed substantially temperature just low the melting point to pro-. of carbon, chromium and tungsten and contflm duce an irreversible hardness. i I

. r I t ,ing 8.5% to 9.0% carbon, 55.0% to 60.0% chro- 3. The process of making a carbide containing and 5 to 36.0% t Estebv composition comprising-mixing particles-of a preformed hard metal ,carbide with o. molten mt T 9 bath containing metal-of the irongroup, retainsufistantially Wham metal of mill-chromium ing particles of the preformed carbide in a sin- 1. 1 carmn; 581d P tered condition in association with th m lt n cast mixture of a molten no utt s bath, casting such mixture toobtain retained l alloy containing cobalt nd. meta-1 f the I sintered particles of preformed carbide carried chromium group. an i d sintered particles of preformed tungsten carbide having the formula WC.

13. A cast non-ferrous composition composed substantially of carbon, chromium, cobalt and tungsten, and containing 1.0% to 7.0% carbon, 7.5% to 15.0% chromium, with the balance cobalt and tungsten the cobalt being not less than 5.0% and tungsten being not less than 38.0%; said composition comprising a cast mixture of a molten non-ferrous cutting tool alloy composed substantially of chromium, tungsten and cobalt and containing 7.0% to 8.0% chromium, 38.0% to 42.0% tungsten and 50.0% to 55.0% cobalt, and retained sintered particles of a preformed hard component composed substantially of car bon, chromium and tungsten, and containing 12.5% to 15.0% chromium, 75.0% to 80.0% tungsten, and about 6.5% to 7.0% carbon.

14. The process of making a composite composition, comprising retaining in a sintered condition, particles of a preformed hard metal component containing a metalloid such as' carbon, in association with molten metal containing metal of the iron group; casting such mixture to obtain retained sintered particles of the preformed hard component carried in a matrix material; powdering such material; and pressing and sintering the powder to a rigid body.

15. The process of making a composite composition, comprising mixing particles of a preformed hard metal component containing a metalloid such as carbon, with a molten bath.

containingv cobalt; retaining particles of the preformed hard component in a sintered condition, in association with the molten bath; casting the mixture to obtain retained sintered particles of the preformed hard component carried in a matrix material; powdering the cast composition; and pressing and sintering the powder to a rigid mass.

16. The process of making a composite composition, comprising forming a casting mixture of retained sintered particles of a preformed hard metal component containing a metalloid such as carbon, and molten metal containing metal of the iron group and metal of the carbide; casting the mixture; powdering-the cast composition; and pressing and sintering the powder to a rigid mass.

17. The process of making a composite composition, comprising forming a casting mixture of retained sintered particles of preformed tungsten carbide and molten metal containing cobalt and tungsten; casting the mixture; powdering the cast composition and pressing and sintering the powder to a.rigid mass.

18. The process of making a composite composition, comprising forming a casting mixture component containing carbon 6.5%

of retained sintered particles of preformed hard metal carbide and molten metal containing cobalt, chromium and tungsten; casting the mixture; powdering the cast composition: and pressing and sintering the powder to a rigid mass.

19. The process of making a composite composition, comprising forming a casting mixture of retained sintered particles of a preformed hard component containing carbon 8.5% to 9.0%, chromium 55.0% to 60.0% and tungsten 32.0% to 36.0%, and molten metal containing metal of the iron group; casting the mixture; powdering the cast composition; and pressing and sintering the powder to a' rigid mass.

20. The process of making a composite composition, comprising forming a casting mixture of retained sintered particles of a preformed hard component containing carbon 8.5% to 9.0%, chromium 55.0% to 60.0%, and tungsten 32.0%

to 36.0%, and molten metal containing cobalt and metal of the chromium group; casting the mixture; powdering the cast composition; and pressing and sintering the powder to a rigid mass.

21.:The process of making a composite composition; comprising forming a casting mixture of retained sintered particles of a preformed hard to 7.0%, chromium 12.5% to 15.0%, and tungsten 75.0% -to 80.0%, and molten metal containing cobalt and metal of the chromium group casting the mixture; powdering the cast composition; and pressing and sintering the powder to a rigid mass.

22. The method of making an alloy composed substantially of carbon, chromium, cobalt and tungsten, and containing 3.5% to 9.0% carbon, 38.0% to 58.0% chromium, and 33.0% to 58.5% cobalt and tungsten, the cobalt being at least 5.0% and the tungsten not less than 15.0%; which comprises mixing particles of a preformed hard component composed substantially of carbon, chromium and tungsten, and containing 8.5% to 9.0% carbon, 55.0% to 60.0% chromium, and 32.0% to 36.0% tungsten with a molten bath composed substantially of cobalt and metal of the chromium group, retaining particles of the preformed hard component in a sintered'condition.

and casting the mixture.

ROY T. WIRTH.