US3807966A

US3807966A - Composite product including magnetic material and method of production thereof

Info

Publication number: US3807966A
Application number: US00200200A
Authority: US
Inventors: J Butcher; T Thexton
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1970-11-26
Filing date: 1971-11-18
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30
Also published as: AT314947B; CH540080A; IT945122B; CA964451A; ES397356A1; FR2116054A5; BE775915A; DE2158166A1; AU3616671A; NL7116021A

Abstract

Method of producing a composite product, including providing within a mold cavity at least two dissimilar powders so that one of such powders adheres to part of or the entire surface that defines the cavity. At least one of the powders can be magnetic, so that the magnetic powder is provided in the cavity under the influence of a magnetic field to locate the magnetic powder at a predetermined position in the cavity in response to the field, another powder being provided in the remainder of the mold cavity, after which the powders are consolidated into a selfsustaining body that can be sintered. The magnetic powder can be a material susceptible to magnetic attraction, such as nickel, iron and/or cobalt, or the individual particles thereof can have an exterior or interior portion of such magnetic material.

Description

United States Patent [191 Butcher et al.

[ COMPOSITE PRODUCT INCLUDING MAGNETIC MATERIAL AND L'IETI-IOD OF PRODUCTION THEREOF [75] Inventors: John William Butcher, Solihull;

Timothy John Thexton, Birmingham, both of England [73] Assignee: The International Nickel Company,

Inc., New York, N.Y.

22 Filed: Nov. 18,1971

211 Appl. No.: 200,200

[52] US. Cl. 29/182.2, 75/208 R, 75/211, 75/214, 75/200, 29/1823, 29/182, 148/103, 148/108 [51] Int. Cl. B22f 1/00, B22f 3/00, 1322f 7/00 [58] Field of Search 75/208, 214, 211, 200; 29/182, 182.2, 182.3; 148/103, 108

[56] References Cited UNITED STATES PATENTS 3,161,504 12/1964 Black et a1 75/208 2,384,215 9/1945 Toulmin, Jr. 75/226 3,359,622 l2/1967 Meyer et a1... 75/208 2,192,743 3/1940 Howe 75/208 3,428,498 2/1969 Heimke 148/103 Apr. 30, 1974 2,148,040 2/1939 Schwarzkopf 75/226 FOREIGN PATENTS OR APPLICATIONS 1,067,539 10/1959 Germany 75/214 Primary ExaminerBenjamin R. Padgett Assistant Examiner-B. Hunt ABSTRACT Method of producing a composite product, including providing within a mold cavity at least two dissimilar powders so that one of such powders adheres to part of or the entire surface that defines the cavity. At least one of the powders can be magnetic, so that the magnetic powder is provided in the cavity under the influence of a magnetic field to locate the magnetic powder at a predetermined position in the cavity in response to the field, another powder being provided in the remainder of the mold cavity, after which the powders are consolidated into a self-sustaining body that can be sintered. The magnetic powder can be a material susceptible to magnetic attraction, such as nickel, iron and/or cobalt, or the individual particles thereof can have an exterior or interior portion of such magnetic material.

9 Claims, No Drawings COMPOSITE PRODUCT INCLUDING MAGNETIC MATERIAL AND METHOD OF PRODUCTION THEREOF The present invention relates to a method of producing a composite powder metallurgy product and to the product made thereby and more particularly to such a product that includes a magnetically attractable material.

Powder metallurgy processes may be employed in making composite articles from two separate powders, in which articles the portion thereof corresponding to one powder wholly or partly surrounds the portion corresponding to the other powder. Normally such articles are circular or cylindrical and are usually hollow, an example being a bearing bushing that includes a first pair of one material with an interior or exterior lining of another material. Another example is a piston ring that includes an interior part of one material with a facing or another material. In producing such articles from two powders, there is considerable difficulty in providing the two powder masses, one adjacent to the other, in a mold in which the powders are to be consolidated, e.g., by pressure compaction, such that there is no extensive intermingling of the particles of the respective powders. The same difficulty arises if, for example, one powder material is to line a recess in a body made from another powder.

It has now been discovered that a special powder metallurgy process enables the production of a composite product from a magnetic powder and a nonmagnetic powder so that a surface-defining portion of the product is substantially or completely composed of magnetic powder. This special process also enables the production of a composite product from at least two powder components with substantially no intermingling of the initial powder components in the mold cavity before consolidation thereof.

It is, therefore, an object of the present invention to provide a method of producing an integral composite body, a surface-defining portion of which comprises a magnetic material, and overlies a second portion thereof of another metallic material.

Another object of the invention is to provide a method of producing a composite body by consolidating a powder charge including at least two dissimilar powders with minimal intermingling of the respective particles thereof.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention is directed to a method of producing a composite article from a plurality of powders, including the step of disposing at least two powders of different composition in a mold cavity so that one of these powders adheres to a part of or the entire cavity-defining surface, such adherence being achieved by a film disposed on the surface or by a magnetic field. In a preferred embodiment one of the powders (referred to herein as the magnetic powder) comprises magnetic material, and another one thereof comprises a dissimilar material, the magnetic powder being provided in a mold cavity under the influence of a magnetic field so that magnetic powder is more concentrated (i.e., the proportion thereof significantly exceeds the average proportion of the magnetic powder in the total powder charge in the mold cavity) at a portion or portions of the mold cavity predetermined by the magnetic field and the remainder of the mold cavity is filled substantially with other, e.g., non-magnetic, powder. A non-magnetic powder can be introduced into the cavity concurrently with the magnetic powder, the magnetic field preferentially attracting the magnetic powder so that it is more concentrated at the predetermined portion or portions of the mold cavity, the non-magnetic powder being more concentrated at other portions of the mold cavity.

Alternatively, the magnetic powder can be introduced first in the mold cavity under the influence of the magnetic field provided by magnetic means and the second powder introduced thereafter so that the powders are substantially completely segregated, the contact therebetween generally being limited to the interface of the powders, and the magnetic powder is substantially concentrated in the cavity region adjacent to the magnetic means.

The powders in the cavity are then consolidated to produce a self-sustaining powder metallurgy product that is sinterable in standard fashion having regard for the melting points of the metals involved. The powder consolidation can be achieved by, for example, mechanical or isostatic pressing or mold sintering.

Generally, the powders employable in the present invention can have a particle size of about 0.5 microns to about 200 microns, and preferably range in size from about 3 to 100 microns. The magnetic powder can consist essentially of a magnetic material (i.e., one that is attractable by a magnet), such as a ferro-magnetic metal; for example, nickel, iron, cobalt, or mixtures or alloys thereof. Alternatively, the magnetic powder can comprise particles made of two or more component parts, one of which parts is of magnetic material and the other of which is of non-magnetic material, such as graphite, for example. Conveniently, non-magnetic materials such as graphite, alumina or other refractory oxides, refractory carbides or non-magnetic metals can be coated, in whole or in part, with a magnetic metal such as nickel, iron or cobalt. Such coating with the magnetic material can be achieved by various techniques, such as vapor deposition, chemical precipitation, electroless deposition, etc.

The quantity of magnetic material in the coated particles should be sufficient to allow the ready attraction thereof by a magnet. For example, the magnetic material component can constitute, on the average, about 5 to about weight per cent, and, more preferably, about 20 to about 60 weight per cent, of a coated particle. Non-magnetic powder materials that can be used as such in the invention include aluminum, copper, tantalum, columbium, tungsten, molybdenum and metal carbides.

Preferably, the magnet is a permanent magnet, such as, for example, a simple bar magnet. Because the magnetic lines of force concentrate at the ends of the magnet, a greater deposit or concentration of magnetic powder will result at the ends than at other areas of the magnet. The magnet can be laminated, e.g., comprised of two or more magnets arranged end to end so that the overall field is made more uniform along its length. A glass-ceramic magnet in which magnetic iron particles are admixed and dispersed within the glass may be used in certain instances, particularly if a specific field pattern obtainable by suitable distribution of the iron particles is desirable. The magnet may even be a temporary magnet, such as an electro-magnet, or a simple magnet produced by induction.

The magnet can have a shape such that it constitutes part of or the entire side wall defining the mold cavity. The magnetic member can be a single piece or include two or more mating parts.

More specifically, in one embodiment, magnetic powder is first provided on a magnetic member that is insertable into the mold cavity and then the magnetic member, with the magnetic powder thereon, is disposed in the mold cavity. With the magnetic member and the magnetic powder in the mold cavity, the other powder is poured into the cavity and then the powder mass is consolidated. Alternatively, the magnetic member can be introduced into the mold cavity and the magnetic powder can then be provided on the magnetic member, as by dusting, for example, after which the other powder is provided in the cavity and the powders consolidated.

The invention is particularly applicable to the production of annular bodies, such as bearings, cylinders or bushings. For example, the present invention allows the production of a bushing or a sleeve of aluminum with a lining of graphite. Of course neither aluminum nor graphite is magnetic, but one of these components, e.g., the graphite powder, can be coated with a magnetic material, preferably nickel, so that it is easily at tracted by a magnet. The graphite particle size can be about 0.5 microns to about 200 microns and the nickel coating thickness can be about 0.1 microns to about 5.0 microns. in the manufacture of such product the preferred steps are the provision of a non-magnetic cylindrical mold open at both ends, insertion into the lower end of the mold of an annular ring which forms the base of the mold cavity, insertion into the opening in the ring of a cylindrical magnet, coating of this magnet with the nickel-coated graphite powder to form a thin layer thereon, filling of the remaining annular cavity with aluminum powder, compression of the powder into a self-sustaining body, as by mechanical compaction, for example, and separation of the magnet from the resulting compacted body. The self-sustaining body can then be sintered according to known techniques, e.g., in hydrogen at a temperature of about 550C to about 650C. Generally, such an annular sintered product will include a first (i.e., inner) part of graphite particles embedded within a matrix of the magnetic material (e.g., nickel) and a physically distinct (i.e., outer) part of aluminum that is radially removed from the first part, these parts generally being concentric.

The nickel-coated graphite powder may be, for example, about 3 microns in particle size and the aluminum powder may be of particle size such as to pass through a IOO-mesh BSS sieve. Typical dimensions of the mold, which may be of any appropriate nonmagnetic material, such as a nickel-chromium-cobalt alloy, are an outside diameter of 2 inches, an inside diameter of l l/l6ths inch and a height of 2% inches. The magnet may be of A-inch diameter and made, for example, of magnetized chromium steel. Where it is desired, the consolidated powder product may have interior and exterior surfaces of the same material (i.e., the magnetic powder material) and an interior of a nonmagnetic material. Of course, the consolidated powder product can be made so that the graphite particles embedded in the magnetic metal matrix form an outer part thereof with the aluminum forming an inner part.

The magnetic powder can easily be formed into a powder layer of about one-sixteenth inch thick simply by sprinkling it around the cylindrical magnet while this is in the mold. An advantage obtained is that the powder tends to become concentrated close to the poles of the magnet, that is to say at each end when a simple bar magnet is used, so that in the resultant bearing bushing, the lining extends radially outwards over the aluminum body at each end. Alternatively, the cylindrical magnet may be coated before it is inserted in the mold cavity, as, for example, by rolling it over powder spread out on a horizontal surface, after which the thus-coated magnet is inserted in the mold.

If an article, such as a piston ring, requiring an external facing of a material such as graphite is being made, an annular magnet can be used, the method involving coating the inner surface of the annular magnet with the magnetic powder, e.g., nickel-coated graphite, and providing a second powder, e.g., aluminum, to the remainder of the mold cavity, and then consolidating the powders.

A particular advantage obtained with the invention is that the magnetic powder can be substantially localized and not extensively mixed with the other powder, with the consequence that the strength of the aluminum or other body of the compact is not reduced.

While the attraction of more powder to the ends of a simple permanent magnet than over the central length when the powder is applied by sprinkling or by rolling the magnet over powder spread on a horizontal surface, gives some advantage where it is desired that in the resulting article the lining extends radially outwards over the body at each end, the uneven distribution becomes too pronounced generally and, therefore, disadvantageous when the resulting article is more than about 12 mm. in axial length. Such a disadvantage can be overcome in another way of carrying out the invention, where the first powder is caused to adhere to a film of a suitable liquid on a part of or the entire cavitydefining surface of the mold, thereby providing a thin layer of such powder. This film material must wet the cavity-defining surface and can be tacky, but this material need not be an adhesive as that term is commonly understood. A particularly suitable such liquid is a silicone material, e.g., hexamethyldisiloxane, which can also act as a lubricant in facilitating the removal of the compact from the mold. After forming the thin layer of powder on the film, the second powder can be poured into the cavity. Of course, when the invention is carried out in this way the lining or facing powder need not be magnetic and may for example be a mixture or composite of metal powder and graphite, but in forming a thin lubricating layer nickel-coated graphite is still very suitable, since the nickel improves the strength and wearresistance of the lubricating layer and causes it to adhere to the lubricant-free bulk of the bearing. Moreover, the only limit on the axial length of the compact is imposed by the practical difficulties in filling a long mold and compacting the powder in it.

The thickness of the layer of the lining or coating powder formed on the film depends largely on the particle size of the powder. Where the powder is 3 microns in average particle size and the object is to provide a very thin lubricating facing or lining, the powder layer can be about 5 microns thick. The invention is particularly useful in the provision of facing or lining layers of up to about 10 or more microns thick; however, thicker 3,807,966 6 layers are easily formed, particularly with the use of up as a coating by the magnet depends upon its flowmagnetic field or by the alternate formation of films of ability, but even nickel powder, which does not flow material to which powders can adhere and layers of fr ly, an be used,

powder par icle adh r ng to e films, P even with The concurrent provision of the various powders to large powder particles the maximum thickness of e 5 the mold cavity in accordance with the present invenpowder layer generally is about 200 micron tion permits the use of a single automatic feeding dean example a f y of carrying the invention vice and a single cavity-filling operation, thereby prowith the use of a liquid film a composite product was viding cost savings m 9 a mold {made of die Steel w h had an Although the present invention has been described in side diameter of 3 inches and an inside diameter of 1 l0 conjunction with preferred embodiments it is to be Inch, and was Provlded a "h dlah'feter e derstood that modifications and variations may be rered the lower end of which fitted mm wheh sorted to without departing from the spirit and scope of formed the base of the mold The core Ted was the invention as those skilled in the art will readily unsprayed with a Solution of hexamethyldishoxane derstand. Such modifications and variations are considcone m acetone. to a fi on Its surfaceland the ered to be within the purview and scope of the invencore rod then dipped mto nickel-coated graphite powtron and appended claims. der. Approximately 0.13 gms. of powder adhered to the we claim: core surface. The coated core rod was then inserted in 1. A sintered powder metallurgy product comprising 2; ggligfi g ggg i ig g a i i gfig gfr gg a relatively wear-resistant facing of about 5 to about poured into the annular cavity and the powders were 200 mlcrops thickness e graphite pamcles then compacted under a pressdre of 15 tonflin When embeddeqm a F mamx of metal Characterized the annular compact was separated from the mold and by being atirached by a magnet a core all the nickel-coated graphite adhered to its interbeckmg a i material dlfieeliem from the p nal surface. The compact was then sintered to a final Sand f' bemg .nter'bonded dlrecfly to the facmg product useful as a bearing and containing a ma or proportion of a metal from the group consisting of aluminum and copper.

In place of aluminum, the body of a bearing having 2 A a. surface layer formed from nickel-coated graphite powfier metanlfrgy product. defined m claim 1, wherein the matrix metal consists esmay consist of other metals or alloys, for example alloys of copper with in, 6%, 5%Sn 95% Cu or 10% sentlally of at least one of "On, nickel and cobalt.

Sn 90% Cu; copper with lead and phosphorus; and composne powfier metahurgy prodlfct as iron with copper. Such alloys may conveniently be fihed m F wherem the male Propomoh of the formed by the use of the following powder mixtures to hackmg aluminumform the body of the bearing 7 4. A composite powder metallurgy product as de- 25 Cu 75 Fe 6.0

The magnetic field can be generated within the cavity 4 fined in claim 1 wherein the major proportion of the by means of, for example, the lower punch of a mebacking is copper. chanical powder press, which punch can be a perma- 5. A composite powder metallurgy product as denent magnet. Alternatively, the lo er punch a be fined in claim 1 wherein the facing comprises nickelused as the core of an electromagnet, for example, in coated graphite particles. which case the punch is magnetized before the powders A powder metallurgical method of producing a are P h fh autemat'c e composite body with at least a portion of the surface feedmg shoe can be e to feed a thereof differing substantially in composition from the ture of the magnetic and non-magnetic powders to the remainder of Said body comprising. cavity. The powder material distribution present in the mold cavity is carried over to the sintered product so a mold ef at lees? that the product includes a greater concentration of havfhg dlsshmlaf eomposmohs and f magnetic powder material at surface-defining portions h eharaeter'sheer at least one of Sam Powders thereof and a higher proportion of non-magnetic po g more gnetically attractable than an ther der material in the other portions. It is noted that theof Said Powdersr f the under the lhflu' portions of thewsvintgred Product includinglnggqetig ence of a magnetic field that preferentially attracts and moves the more magnetic powder toward an powder in greater concentration can al so inelude small i mterror surface of the cavity to thereby provide a concentration of the magnetic powder at a predeamounts of the non-magnetic material.

A sintered product made in the above manner can be used as a seal for a rotor of a rotary internal combuslh s rf ce P elheh. YYlPhlSi' aY L t and tion engine, for example, where the magnetic powder b. consolidating said powders, while maintaining said comprises nickel-coated graphite and the second powconcentration of magnetic powder at the predeterder comprises aluminum. mined surface position, to produce a self-sustaining Naturally, the ease with which the powder is picked body having a surface portion differing substan- 7 tially in composition from the remainder of the body. 7

7. A method of producing a composite body as defined in claim 6, wherein said powders are introduced concurrently into said cavity.

8. A process as set forth in claim 6 wherein the more magnetically attractable powder is introduced into the mold cavity and is magnetically moved to the predetermined surface position within the cavity prior to the introduction of another powder into the mold cavity.

9. A powder metallurgical process using two different powders for manufacture of a compacted powder metallurgical product having one of the powders in a surface layer portion bonded to a second portion containing the second powder, wherein the first powder is a magnetically attractable material and is of a chemical composition different from the chemical composition of the second powder, comprising:

a. magnetically attracting and moving particles of the first powder into close proximity with a mold cavity wall to provide a layer of the first powder at said cavity wall;

b magnetically maintaining the layer of the first powder at said cavity wall;

c. introducing the second powder into the mold cavity and disposing the second powder against the first powder layer while maintaining the first powder in close proximity with said cavity wall and segregated from the second powder;

d. compacting the two powders together under pressure sufficient to produce a self-sustaining powder metallurgical product; and

e. ejecting the compacted product to obtain a selfsustaining powder metallurgical product having a surface layer portion that differs substantially in composition from the other portion of the product.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,807,966

DATED April 30, 1974 INVENTOR(S) John William Butcher and Timothy John Thexton It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Front page should read at left hand column:

[30] Foreign Application Priority Data 11/26/70 GreatBritain 56269/70 11/ 3/71 Great Britain 5l2ILl/7l Col, 1, line 16, for "pair" read "part- Line 20, for "or" read "of",

Signed and Sealed this ninth Day of September 1975 [SEAL] A ttes r.-

RUTH C. MASON C. MARSHALL DANN Alluring Officer (mmnissimu'r uj'larenrs and Trademarks

Claims

2. A composite powder metallurgy product as defined in claim 1, wherein the matrix metal consists essentially of at least one of iron, nickel and cobalt.
3. A composite powder metallurgy product as defined in claim 1 wherein the major proportion of the backing is aluminum.
4. A composite powder metallurgy product as defined in claim 1 wherein the major proportion of the backing is copper.
5. A composite powder metallurgy product as defined in claim 1 wherein the facing comprises nickel-coated graphite particles.
6. A powder metallurgical method of producing a composite body with at least a portion of the surface thereof differing substantially in composition from the remainder of said body, comprising: a. introducing into a mold cavity at least two powders having dissimilar compositions and dissimilar magnetic characteristics, at least one of said powders being more magnetically attractable than another of said powders, while the cavity is under the influence of a magnetic field that preferentially attracts and moves the more magnetic powder toward an interior surface of the cavity to thereby provide a concentration of the magnetic powder at a predetermined surface position within said cavity, and b. consolidating said powders, while maintaining said concentration of magnetic powder at the predetermined surface position, to produce a self-sustaining body having a surface portion differing substantially in composition from the remainder of the body.
7. A method of producing a composite body as defined in claim 6, wherein said powders are introduced concurrently into said cavity.
8. A process as set forth in claim 6 wherein the more magnetically attractable powder is introduced into the mold cavity and is magnetically moved to the predetermined surface position within the cavity prior to the introduction of another powder into the mold cavity.
9. A powder metallurgical process using two different powders for manufacture of a compacted powder metallurgical product having one of the powders in a surface layer portion bonded to a second portion containing the second powder, wherein the first powder is a magnetically attractable material and is of a chemical composition different from the chemical composition of the second powder, comprising: a. magnetically attracting and moving particles of the first powder into close proximity with a mold cavity wall to provide a layer of the first powder at said cavity wall; b. magnetically maintaining the layer of the first powder at said cavity wall; c. introducing the second powder into the mold cavity and disposing the second powder against the first powder layer while maintaining the first powder in close proximity with said cavity wall and segregated from the second powder; d. compacting the two powders together under pressure sufficient to produce a self-sustaining powder metallurgical product; and e. ejecting the compacted product to obtain a self-sustaining powder metallurgical product having a surface layer portion that differs substantially in composition from the other portion of the product.