US3110091A - Refractory compact manufacture - Google Patents

Description

7 NOW 1963 E. L. LITTLE, JR.. ETAL 3,110,091

REFRACTORY COMPACT MANUFACTURE Filed Dec. 23, 1960 FIG. 4

H62 INVENTORS ERNEST L. LITTLE, JR. HARRY J. McCAULEY FRANK J. PENOZA BY Wan :7

ATTORNEY United States Patent 3,110,091 REFRACTORY COMPACT MANUFACTURE Ernest L. Little, Jr., Harry J. McCauley, and Frank J.

Penoza, Wilmington, DeL, assignors toE. I. du Pont de Nemonrs and Company, Wilmington, Del, 21 corporation of Delaware Filed Dec. 23, 196i), Ser. No. 73,088 8 Claims. (Cl. 29-1825) This invention relates to the manufacture of molybdenum-nitrogen-silicon alloy compacts, and particularly to a method and composition for the manufacture of selected molybdenum-nitrogen-silicon alloy compacts in the form of shaped objects having high inherent lubricity and improved toughness such as is required in hot metal extrusion die nibs, bearings and other articles as to which there is metal-to-metal contact at elevated temperatures.

There is a steadily growing need for metal-forming apparatus, bearings and other devices exhibiting a low coeflicient of friction coupled with high temperature and erosion resistance and resort has been had to a variety of refractory materials for this purpose. However, there has been a marked deficiency with respect to inherent lubricity, especially, by which is meant the slipperiness displayed by a material. In addition, it has proved very difiicult, if not impossible, to form these substances with apertures such as bores, partial bores or even generally concave surfaces, due to inherent brittleness, hardness, abrasiveness and other unfavorable characteristics, and this is particularly true where the apertures must be formed to high dimensional precision and are, in service subjected to terrific loading stresses and temperatures, such as exist with hot metal extrusion die nibs and, in extreme cases, with bearings. Finally, most refractory materials are low in tensile strength and are difficult to mount in supports giving the necessary back-up strength.

It is an object of this invention to provide a composition and method for the manufacture of improved compacts of high inherent lubricity and toughness consisting mainly of molybdenum, silicon, nitrogen and at least one of the three metal oxides ZrO ZnO and Cr O It is another object of this invention to provide a modified nitrogen-containing molybdenum silicide compact which is amenable to the inclusion of apertures in the structure. It is a further object of this invention to provide a composition which is adapted to the fabrication of hot metal extrusion die nibs, bearings and similar structures having high dimensional stability and relatively low cost. The manner in which these and other objects of this invention are attained will become apparent from the following detailed description and the drawings, in which:

FIG. 1 is a vertical sectional view of a preferred aspressed shape of compact for the manufacture of a die nib according to this invention, wherein cross-hatching has been partly omitted to better show the several dimensional attributes,

FIG. 1a is a vertical sectional view of the compact of FIG. 1 in the as-finished form of a die nib and in condition to be mounted in a suitable holder for metal extrusion, the flare of the discharge opening being somewhat exaggerated to show this detail,

FIG. 2 is a vertical sectional view of a preferred embodiment of graphite die mold adapted to the manufacture of compacts of the design shown in FIG. 1,

FIG. 3 is a fragmentary view in transverse section through the extrusion throat of a special design of die nib adapted to form fluted metal rods by hot extrusion, and

FIG. 4 is a sketch copying a small section of a 100 0 photomicrograph of an etched metallographic specimen "ice cut from a typical MoNSiZrO hot metal extrusion die.

Generally, this invention comprises a composition useful in the fabrication of compacts which have a high inherent lubricity and improved toughness Consisting essentially of 2053% Si, 40-65% M0, 119% N and from about 5-20% of a metal oxide taken from the group consisting of ZrO ZnO and Cr O and also a method of manufacturing such compacts.

Ne have found (refer to copending US. application S.N. 78,102 filed of even date herewith) that certain trimetal systems, such as Fe--Mo-Si, FeSiTi and MoNSi-Ti, are improved substantially in physical properties by the addition thereto of one or more of the specific metal oxides ZrO ZnO and Cr O followed by sintering of the intimately mixed ingredients by conjoint use of heat and pressure. Our investigation has now shown that the bi-metal system MHi containing chemically combined N (which is disclosed in US. application S.N. 793,922), at least within a critical composition range, is also benefited by inclusion of one or more of the metal oxides hereinbefore mentioned, and it is to this advance that this application is directed.

It is ditficult to isolate the most important result of metal oxide addition, since the characteristics of the manufactured product must be appraised as a composite on the basis of use tests. Nevertheless, it appears that the metal oxides enhance the lubricity of the compacts and, at the same time, serve a useful function in the prevention of cracking or disintegration during the high pressure consolidation necessary to the production of high density compacts of good strength and erosion resistance.

Moreover, the metal oxide additive is advantageous also from the standpoint of aperture formation in the compacts, and this is true for both the situation wherein the apertures are molded, at least in the rough, during the consolidation by which the compact itself is formed or where the apertures are formed in the compact by later machining operations. Finally, the metal oxide additives appear to impart a toughness to the compacts which enable them to withstand stresses imposed on them during pressing or shrinking occurring in the mounting of the compacts within associated support housings.

This invention is hereinafter described with particular reference to the manufacture of hot metal extrusion die nibs, because the fabrication of these devices requires, to an exceptional degree, the overcoming of problems of precise dimensional control, the formation of apertures in the compacts and the like which are common to other structures such as bearings and similar apertured devices as to which this invention is also applicable. In all cases, powdered metallurgy techniques are employed in the manufacture, the compositions of this invention consisting in original, unalloyed, unsintered form of metal powder mixtures which are, however, converted to alloys during the sintering by conjoint use of heat and pressure. Thereafter, for use as die nibs, the compacts are mounted in suitable support housings, such as described in copending U.S. application S.N. 78,165, filed of even date herewith, which confer uniform high strength support for the compositions over the wide temperature ranges in which hot metal extrusions are conducted.

Metal forming by the extrusion technique is particularly advantageous from the following standpoints: the ability to form relatively complex shapes in a single pass, easy change-over from one shape product to another, short lead time in production, ease of design change, reduced Working capital and increased processing yields. In addition, the die nibs of this invention make it possible to dispense with extrusion lubricants either entirely, or to a very great extent, which gives an improved product quality in terms of both surface finish and tolerance, as well as eliminates cleansing problems. 'It appears, also, that the new die nibs make it possible to extrude new metals and alloys in new shapes never before achieved by the industry.

The ability to dispense with lubricants in metal extrusion is a particularly important advance, since the use of such lubricants has been hitherto considered to be almost axiomatic in the art. For metals which can be worked at temperatures under about 500 C., such as Al and Mg, for example, hydrocarbon oils have been used as extrusion lubricants. However, for the higher temperatures required for the extrusion forming of copper, steel, ferrous alloys and refractory metals there is difficulty in finding a lubricant which possesses suitable viscosity and stability. Graphite is widely used for the coating of the metal feed input passages, which are referred to in the art as the containers, leading to the die nibs, and sometimes the die nibs themselves; however, graphite does not provide the continuously moving film possessed by a fluid lubricant. Recently, molten glasses, molten salts, clay-graphite mixtures and specially compounded greases have aided metal extrussions in the higher temperature range above 1000 C., but these have also been deficient, in that the lubricant film has not been continuously maintained and, where it has failed, there has been objectionable galling of the extrudate accom panied by accelerated and uneven wear on the die nibs. Lubricant failure in the extrusion of soft metals, such as aluminum, can oftentimes be tolerated from the standpoint of die nib wear, because the nib life remains still quite long; however, where steels, ferrous alloys and refractory metals are being extruded, the nib life is drastically reduced and is frequently measured in terms of only 1-10 pushes per die nib.

The importance of die nibs of maximum resistance to erosion is evident, because the dimensional tolerance and surface finish of the extrudate product is directly dependent thereon. It is at least equally important, though, to eliminate lubricants in all extrusion work if at all possible, since lubricants remaining on the product are a contaminant which must thereafter be removed by degreasing, or even by grit blasting and pickling in the case of glass lubricants, which is expensive, time-consuming, and frequently harmful to the product because of corrosion, oxidation promotion or the like. Finally, lubricant failure becomes more serious where the extrudate product has fins, projections, sharp edges, re-entrant angles and other shape peculiarities, because the lubricant cannot readily adapt itself to accommodation of these features. The trend, however, is to produce by metal extrusion products which are increasingly complex in cross-sectional profile and thus there is a clear neces-- sity for lubricant elimination in view of this consideration also.

The conversion of the powdered compositions to solid compacts as hereinafter described generally involves calorescence (i.e., an exothermic reaction characterized by an increase in temperature as evidenced by an increase in luminosity) that is induced when a considerable portion of the consolidated powder is heated to a temperature of at least 900 C. The internal temperature of the mass during this conversion reaches 1100-l600 C. When the spontaneous heat increase due to calorescence is low, the temperature to achieve conversion must be raised by external heat application. The metal Si is so exothermic in its reaction with other metal constitutents that it can generate extreme heat, which sometimes even appears capable of vaporizing some of the constituents. Accordingly, it is preferred that at least a part of the Si be utilized according to this invention as a compound with some other element, e.g., as silicone nitride, molybdenum disilicide, or the like. However, molybdenum can be utilized in elemental form.

The purity of commercial grade MoSi is generally about 99%, whereas that of silicon nitride is typically 92%. Elemental molybdenum is available at 99% purity, or even higher. We have found that compacts made from the relatively impure binary alloys have proved completely satisfactory in service, even though there are appreciable quantities of inert diluents, e.g., Al, Mn, Ca, Mg, Cu and Ni present, either as elements or oxides. In general, it is preferred that these inert substances be below about 5%, or even better, below 3% in the starting materials as received. An additional consideration is that the ball milling size reduction operation inevitably adds a small amount of silica or alumina, and perhaps minor amounts of other substances as a consequence of attrition of the grinding elements.

In general, we have found that compositions in the range of about 20-53% Si, 4065% Mo, 1-19% N and from about 520% of a metal oxide taken from the group consisting of ZrO ZnO and Cr O are satisfactory for the purposes of this invention. As taught in US. application S.N. 793,922 hereinbefore referred to, it is often helpful to moisten the powder with a liquid, eg, Water, to assist in forming it to the desired shape. Aqueous solutions of sodium hydroxide containing a few percent, i.e., 1-5% NaOH are particularly desirable for this purpose. The small amount of sodium hydroxide contained in the composition after drying leads to the formation of alloy objects having improved properties.

A typical composition according to this invention, ignoring the relatively small amounts of inerts present, is that made up from a powder containing 58.7 M0, 7.1 N, 34.2 Si, to which ZrO in the amount of 10% by Weight is added.

This composition was formulated as follows: 250 gms. of molybdenum powder (200 mesh), 500 gms. of MoSi powder (200 mesh) and 220 gms. of silicon nitride (-325 mesh) were milled together in a one-gallon capacity porcelain jar mill to which were added 3000 gms. of flint pebbles. A liquid additive consisting of 1000 cc. of benzene was added to prevent compaction of the powder during the ball milling and the ball mill was operated for 72 hours at a speed of 40 r.p.m. The product was thereafter dried for 16 hours in an air atmosphere in an electric oven maintained at C., after which it was screened through a 200 mesh sieve.

To the dried powder mixture hereinbefore described was added 108 gms. of dry ZrO preground separately at substantially the same speed and for the same time. The two powdered portions were intimately mixed together with the aid of a conventional electrical 'blender, after which electron microscope examinations showed that there was obtained a homogeneous mixture wherein most particles were 1-3 microns in size, although an appreciahle number were below 1 micron and there were a few somewhat larger, in the extreme case up to about 10 microns. Particle size control within this range is preferred for best results; however, acceptable products are obtained where the particle size is less than about 75 microns, of which at least 75% by weight are less than about 5 microns. It will be understood that fluid energy mills, or other designs, can be substituted for ball milling if desired.

The individual or co-mixed powders can be stored indefinitely in glass bottles provided with plastic caps Without deterioration; however, it is preferred to store them in an air-conditioned room maintained at a temperature of about 24 C. and a relative humidity of about 40% to maintain the physical handling properties unaltered, which is an aid in the later manufacturing operations.

Turning now to extrusion die nib manufacture per se, a typical die nib had the as-pressed shape of FIG. 1 and was thereafter finished to the final shape of FIG. 10, after which it was mounted in a suitable support housing and was then ready for use in metal extrusion. It will be understood that an extremely wide variety of die nib shapes can be fabricated according to this invention, and that some shapes perform better than others as regards specific metals to be extruded, reduction ratios, rate of extrudate throughput, extrusion temperatures, whether or not lubricants are used during the extrusion and many other considerations. The design described is a highly eflective one and is well-suited to hot metal extrusions.

The specific nib, tested as hereinafter described, measured, in the finished form shown in FIG. 1a, 1%" dia. x 1" long overall. The extruding inlet was provided with a frusto-conical mouth sloped at an angle of about 45 and of a depth b, which measured 0.5". The length 12 of the straight cylindrical throat c was /a", and the surfaces of both the inlet and throat were ground and polished to a high finish, the finished diameter of throat 0 being 0.6 25. In the finishing operation, the extruding outlet was shaped to an outwardly expanding taper g of 2-5", the degree of taper within the limits given being rather non-critical.

It was found that the best compaction in manufacture was obtained by pressing the nibs first into the shape of FIG. 1, in which they were also sintered and interalloyed, and thereafter machining them into the shape of FIG. 1a. The profile f bell mouth shown in FIG. 1 is actually that formed by two concentric frusto-conical surfaces, the outer one of which is inclined to the horizontal at an angle a= whereas the inner one is inclined to the vertical at an angle e=45. These two surfaces intersect in a toroidal surface which is formed to a radius f of 0.02", the lower extremity of which surface is located on the level of line x-x a distance d=% inwardly from the outside circumference of the nib body as pressed. The straight cylindrical throat of FIG. 1a measured 0.609" as rough-formed. The specific profile of bell-mouth described appears to be particularly advantageous from the standpoint of ready disengagement of the compaction mold piston. As indicated in FIGS. 1 and 1a the top of the nib is ground oif on line x-x as a finishing operation to obtain the nib form of FIG. 1a.

The nib was formed by molding within a graphite die mold which, as shown in FIG. 2, comprises a cylindrical body 10 about 5 /2" in height provided centrally with, a bore 9 of the same size as the unfinished outside diameter of the die nib it is desired to form. Bore 9 constitutes the mold cavity and is provided at the lower end with a close-fitting annular graphite base plate 11 drilled centrally to receive a solid cylindrical graphite core piece 12 of a diameter equal to that of the unfinished throat c of the nib to be formed. The bore is also provided with a close-fitting plunger 17 formed at its lower end with a concave surface which is the exact reverse configuration of the bell mouth of FIG. 1 which is to be formed in the nib. To permit easy relative movement of plunger 17 axially with respect to core piece 12, a clearance of 0.001"-0.0015" is provided therebet-ween. Finally, a A;" diameter thermocouple well 18 is preferably provided in body 10.

In nib manufacture, it will be understood that a complete Weighed and mixed powder charge, dried to below about 3% moisture conent as a maximum, is first placed within bore 9, closed at the bottom by base plate 11 and provided with core piece 12, if the die throat is to be preformed. The charge is then tamped manually with the aid of plunger 17 until enough powder has been introduced into the mold to produce a nib of the length desired. At this point the entire mold and its charge is placed upright within a hydraulic press and pressure applied to plunger 17 while base plate 11 is supported in place by the press platen and the entire die mold is heated, preferably by electric induction heating, until the alloying and sintering hereinbefore described is completed. It is preferred to shield the die mold with two or more thicknesses of asbestos paper wrapped circumferentially around the outside of body 10, and also on the top and bottom surfaces of the die mold, to preserve uniform temperature conditions within the die mold and, at the same time, protect the mold from oxidation by the air.

A preferred procedure for the manufacture of die nibs of MoNSiZrO composition is to apply 1000 p.s.i. at room temperature, then heat the mold with this pressure applied by electrical induction to a temperature of about 1200 C. within about 8 mins. The pressure is then increased to 2000 p.s.i. and heating continued under pressure to a temperature level of about 1600 C., which requires an additional time of 5 mins. Then the pressure is increased to 3000 p.s.i. and the object maintained at this pressure and at a temperature of about 1600 C. for a soaking period of 30 minutes. Thereafter, the temperature is increased to 1650 C. within one minutes time and the pressure increased to 4000 p.s.1. A five minute soak at the latter temperature and pressure completes the sintering, and heat and pressure are discontinued.

Core pin 12 is then removed from the hot mold by forcing it out with an arbor press, after which the hot mold, still containing the nib within its cavity, is placed within a metal container which is loaded with alumina spheres. The mold is covered with the spheres, which shield the mold from oxidation, and allowed to cool to room temperature, after which the mold is placed in an arbor press and plunger 17 pushed downwardly without support applied to the underside of base plate 11. This forces plate 11 and sintered nib 16 out of the bottom of the graphite mold, after which the mold can be reloaded to make another nib. It will be understood that the mold and its appurtenances can be used over and over again indefinitely.

The surface areas of the nib are belt-sanded and, thereafter, ground to parallel surfaces at top and bottom, as well as to desired height, using a silicon carbide or diamond grinding wheel. The frusto-conical inlet and the nib throat are then finished, both as regards surface quality and dimensions. Finally, the nib is formed oircumferentially to fit within an elastic metal support housing as described in copending US. application S.N. 78,165, hereinbefore mentioned, after whichthe complete die is ready for hot metal extrusion service.

It is preferred to mold-form the nib throats at least to rough polished state, in the course of manufacture of the nibs themselves, because in this way complete extrusion passages can be delineated by simply machining the reverse configuration on the outside of the easily machinable graphite core pin 12. One such intricate transverse throat profile is that shown in FIG. 3, which was adapted to produce fluted extruded rods of copper, steel, tool steel and niobium. However, if desired, the nib extrusion passages can be formed by electrospark machining, diamond boning or ultrasonic machining.

The foregoing description is directed specifically to a single firing procedure for the manufacture of compacts; however, it will be understood that a partly or fully reacted and allowed compact can be pulverized and resintered int-o absolutely sound compacts having all of the beneficial properties of this invention. This latter is sometimes an advantageous procedure where the calorescence is so vigorous as to produce blow holes in the original compact, since the complete physical structure is reconstituted in dense, homogeneous condition by the second sintering.

The inherent lubricity and toughness possessed by compact made according to this invention is demonstrated by the following hot metal extrusion tests conducted with the specific die nib herein described in detail. This nib had a Rockwell A hardness of 85, 90, as measured in two spaced determinations, and a density of 4.82 gms./cm. The die design utilized was that shown in FIGURE 7 of US. application S.N. 78,165 hereinbefore mentioned, which utilizes a ring housing enclosing the nib circumferentially together with a separate base portion, drilled centrally to clear the nib outlet, which supplies axial support for the construction. The ring housing was fabricated from a material which displays a smaller thermal coefiicient of expansion over at least a substantial portion of the temperature range involved than does the metal silicide nib. Thus, employing a relatively small interference fit in the cold assembly, the bonding joinder becomes tighter with temperature rise. This contributes a progressively greater tangential compressive stress with rise in temperature, so that the sum of nib tensile strength plus tangential compressive stress is sufficient to offset the disruptive loading imposed on the nib by hot metal extrusion. A suitable material of construction for the ring housing is Ferro-Tic C, a product of the Sinter Cast Division, Chromalloy Corporation, which consists of titanium carbide grains cemented together with a steel binder. This material has a modulus of elasticity of 44 mm., which is advantageous in that there is good stress transfer from nib to housing as a separate feature. The nib was assembled within the housing by press fit at room temperature utilizing a 1 reducing taper in the direction of metal extrusion for both nib and housing, and an 0.008" diametrical interference between the parts.

This die was utilized for the hot extrusion of four different materials in the sequence hereinafter recited Without the use of any lubricants whatever. The reduc tion ratio was 4.5 to 1 in all instances, by which is meant the ratio of cross-sectional area of billet fed to extrudate product. The term nib washout refers to progressive enlargement of the nib mouth occurring as a consequence of extrusion.

A. The extruded material was brass analyzing 61.5% Cu, 35.5% Zn, 3% Pb, the billets fed measuring 1 dia. x 1 /2" long. These were preheated to 1350 F. and the die itself was preheated to 850 F. to safeguard against chilling the metal fed.

Two extrudate rods were made, both of which had high surface quality. There was no nib washout, nor any damage to the die.

B. The extruded material was metallic copper analyzing 99.9% pure, which was fed in as billets measuring 1 i dia. x 1 /2" long, preheated to 1500 F., with the die preheated to 850 F.

Two extrudate rods were made, each having high surface quality, without any perceptible nib washout or damage to the die.

C. The extruded material was A.I.S.I. 1018 steel having the general analysis 0.15O.20% C, 0.600.90% Mn, 0.040% (max.) P, 0.050% (max.) S, balance Fe. The steel was fed as billets measuring 1 dia. x 1 /2 long, preheated to 2100 F., and the die was preheated to 850 F.

Two extrudate rods were formed, each of which had high surface quality, and there was no accompanying nib washout or die damage.

D. The extruded material was a niobium alloy analyzing 10% Ti, 10% Mo and 80% niobium. This was fed to the die as a billet measuring 1%," dia. x 2 /2" long, preheated to 2700 F., the die being preheated to 1100 F.

A single extruded rod was formed approximately 10" long, which had a good surface quality, and there was no accompanying nib washout or die damage.

From the foregoing, it is apparent that compacts made according to this invention possess remarkable inherent lubricity and toughness, which makes it possible to extrude metal billets having temperatures up to about 6000 F., where suitably cooled die nibs are employed or, alternatively, where the extrusion is conducted at a high enough rate to complete it before there is destructive heat transmission to the die.

Extensive metallographic study under magnifications of 100-l000 on sections taken from die nibs and tool bits prepared in accordance herewith has shown a microstructure such as that of FIG. 4, which is that of an etched 11 50 15% HNO HF, balance H O ctchant) specimen at 1000 taken from a die nib of the specific composition hereinbefore reported. The compact is seen to consist of two essential phases, the first, denoted p, being a white, hard, continuous phase having an approximate 1200 Knoop hardness at 100 gms. load, abbreviated 1200 K whereas the second, denoted q, is a softer (ca. 600 K black, discontinuous phase which is vitreous in nature. A fine-grained microstructure in the compact also appears to be beneficial, e.g., 110 micron size with an average grain size of 5 microns. From this last fact, it is seen that virtually no grain growth occurs during the hot pressing-sintering, the initial milled powders falling in the same 1-5 micron particle size.

One theory which can be postulated is that the dark vitreous phase becomes progressively less viscous as the temperature is raised, while still being retained in situ by the hard, strong, rigid matrix, so that it affords a lubricating action against sliding contact with the compact. Regardless of the true explanation, however, there is an established high-order lubricity evidenced during extremely severe tests, such as those represented by the hot metal extrusions described.

A statistical appraisal of sample performance in all aspects, extending from ease of hot-pressing, e.g., avoidance of sticking in the mold, elimination of cracking and the like, through mounting die nibs in their holders, e.g., toughness and strength in resisting the stresses applied at this stage, to final performance as hot metal extrusion dies indicates that ZrO is generally superior as an additive to either ZNO or Cr O However, the demands of particular installations are so diverse and specialized that the latter two metal oxides can well have unique applications exclusive to each.

The ability to form intricately shaped compacts, such as the apertured nib hereinbefore utilized as the prime example for purposes of this description, is an exceedingly important consideration. Industrial usage depends to a large extent on the ease with which objects can be shaped, and compacts according to this invention can be made in sprerical form as well as with a variety of shapes, curved surfaces and the like. It will be understood that it is often times not necessary to prepare a die, bearing or similar structure as a unitary object, but that it can be fabricated as a multiplicity of interfitting segments which, in assembly together, make up the entirety. Such a design approach is entirely feasible in view of all of the desirable physical characteristics of the compositions of this invention.

From the foregoing, it will be understood that relative ly wide modifications can be made in composition, manufacturing pressures, temperatures and other factors without departure from the essential spirit of this invention, and it is intended to be limited only by the scope of the following claims.

What is claimed is:

1. A powder metallurgy composition useful in the fabrication of shaped objects having high inherent lubricity and toughness consisting essentially of 2053% Si, 40-65% Mo, l19% N and from about 520% of a metal oxide taken from the group consisting of ZrO ZnO and Cr O wherein the size of all particles is less than about microns and of which at least 75% by weight are less than about 5 microns.

2. A powder metallurgy composition useful in the fabrication of shaped objects having high inherent lubricity and toughness according to claim 1 wherein said metal oxide consists substantially solely of ZrO 3. A powder metallurgy composition useful in the fabrication of shaped objects having high inherent lubricity and toughness consisting essentially of 2053% Si, 40-65% Mo, 1l9% N and from about 520% of a metal oxide taken from the group consisting of ZIO2, ZNO and Cr O wherein the content of inert substances commingled therewith is less than about 5% by weight and the size of most particles therein is between about 1-3 microns with the maximum particle size about 10 microns.

4. As a manufacture, a shaped object having a high having high inherent lubricity and toughness comprising concurrently heating and pressing a powder mixture consisting essentially of 20-53% Si, 4065% Mo, 119% N and from about 520% of a metal oxide taken from the inherent lubricity and toughness comprising a powder 5 group consisting of ZrO ZnO and Cr O wherein the metallurgy composition sintered and alloyed to a substansize of all particles is less than about 75 microns and of tially homogeneous composite; said powder metallurgy which at least 75% by weight are less than about 5 composition consisting essentially of 2053% Si, 40- microns, in a staged sequence consisting of maintaining 65% Mo, 119% N and from about 5-20% of a metal a pressure of about 1000 psi. while heating said powder oxide taken from the group consisting of ZrO ZnO, 1 mixture from room temeprature to about 1200 C., then and Cr O wherein the size of all particles is less than increasing the pressure to about 2000 psi. and maintainabout 75 microns and of which at least 75% by weight ing this last-mentioned pressure while raising the temare less than about microns. perature to about 1600 C., then increasing the pressure 5. A composition useful in the fabrication of shaped to about 3000 psi. while maintaining the temperature at objects consisting essentially of 53% Si, 65% 15 about 1600 C. for a period of about 30 minutes, and Mo, 1l9% N and from about 520% of a metal oxide then, finally, raising the temperature to about taken f the group consisting f ZIOZ, 0 and @203, while maintaining the pressure at about 4000 p.s.1. for a wherein the size of all particles is less than about E of about mlmlte? t9 efiect cofnpletlon 0f the microns and of which at least 75 by weight are less smtenng and alloymg of sald Powder mlxture' than about 5 microns. 20 v 6. A composition of claim 5 in which the metal oxide References cued m the file of thls Patent consists substantially solely of ZrO UNITED STATES PATENTS 7. A shaped object of claim 4 in which the metal 2,866,259 Bechtold Dec, 30,1958 oxide consists substantially solely of ZrO 25 2,878,113 Bechtold Mar. 17, 1959 8. A method for the manufacture of shaped objects 2,982,619 Long May 2, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,110,091

November 12, 1963 Ernest L, Little, Jr, et al3 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 9,

a line 2, after "size" insert below 10, line 10, for temeprature read temperature Signed and sealed this 5th day of May 1964.,

(SEAL) Attest:

ERNEST W, SWIDER 3 column EDWARD Je BRENNER Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 1lO O9l November 12 1963 Ernest L. Little, Jr. 9 et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belo C iolumn 9, line 2 after "size" insert below column 10 line 10, for "temeprature" read temperature Signed and sealed this 5th day of May 1964.

(SEAL) Attest:

ERNEST Wc SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (2)

1. A POWDER METALLURGY COMPOSITION USEFUL IN THE FABRICATION OF SHAPED OBJECTS HAVING HIGH INHERENT LUBRICITY AND TOUGHNESS CONSISTING ESSENTIALLY OF 20-53% SI, 40-65% MO, 1-19% N AND FROM ABOUT 5-20% OF A METAL OXIDE TAKEN FROM THE GROUP CONSISTING OF ZRO2, ZNO AND CR2O3, WHEREIN THE SIZE OF ALL PARTICLES IF LESS THAN ABOUT 75 MICRONS AND OF WHICH AT LEAST 75% BY WEIGHT ARE LESS THAN ABOUT 5 MICRONS.

8. A METHOD FOR THE MANUFACTURE OF SHAPED OBJECTS HAVING HIGH INHERENT LUBRICITY AND TOUGHNESS COMPRISING CONCURRENTLY HEATING AND PRESSING A POWDER MIXTURE CONSISTING ESSENTIALLY OF 20-53% SI, 40-65% MO, 1-19% N AND FROM ABOUT 5-20% OF A METAL OXIDE TAKEN FROM THE GROUP CONSISTING OF ZRO2, ZNO AND CR2O3, WHEREIN THE SIZE OF ALL PARTICLES IS LESS THAN ABOUT 75 MICRONS AND OF WHICH AT LEAST 75% BY WEIGHT ARE LESS THAN ABOUT 5 MICRONS, IN A STAGED SEQUENCE CONSISTING OF MAINTAINING A PRESSURE OF ABOUT 1000 P.S.I. WHILE HEATING SAID POWDER MIXTURE FROM ROOM TEMPERATURE TO ABOUT 1200*C., THEN INCREASING THE PRESSURE TO ABOUT 2000 P.S.I. AND MAINTAINING THIS LAST-MENTIONED PRESSURE WHILE RAISING THE TEMPERATURE TO ABOUT 1600*C., THEN INCREASING THE PRESSURE TO ABOUT 3000 P.S.I. WHILE MAINTAINING THE TEMPERATURE AT ABOUT 1600*C. FOR A PERIOD OF ABOUT 30 MINUTES, AND THEN, FINALLY, RAISING THE TEMPERATURE TO ABOUT 1650*C. WHILE MAINTAINING THE PRESSURE AT ABOUT 4000 P.S.I. FOR A PERIOD OF ABOUT 5-6 MINUTES TO EFFECT COMPLETION OF THE SINTERING AND ALLOYING OF SAID POWDER MIXTURE.

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