2,799,912 Patented July 23, - 1957

2 merci-al manufacture, particularly since in some instances it is very desirable to provide for ‘a ?nal forming step 2,799,912 intermediate the initial forming and ?nal ?ring. In such PROCESSES FOR FQRME’NG HIGH TEMPERATURE instance, it is necessary to bisque ?re or sinter the compact CEIC ARTICLES at very high temperatures to obtain a sufficient hardness where grinding with conventional means is possible. Herbert Hans Gregor, Rockville, Md. Certain improvements over the above sintering method No Drawing. Application December 18, 1950, have been obtained by the addition of small quantities of Serial No. 201,483 r metal, such as cobalt or nickel powder, which causes the 10 carbide to sinter at lower temperatures. The added metal 2 Claims. (Cl. 25-156) is subsequently volatilized in vacuum at high tempera (Granted under Title 35, U. S. Code (1952), see. 266) tures, thus leaving the pure carbide. Yet even this im provement is cumbersome ‘and of limited ?exibility for commercial practice. The present invention relates generally to the fabrica 15 The di?iculties and limitations of current practices are tion of molded high temperature ceramic articles, and essentially avoided and overcome by the process of the more particularly to a process and compositions for the present invention. Considerable freedom is obtained not manufacture of carbide-bonded, boride-bonded, or simi only in iorming the compact, but also in the ?nal prop; larly bonded articles of metal carbides, borides, and like erties of the article by a suitable choice of» molding com a: , compounds by sintering, wherein the bond ‘for the base positions compounded in accordance with chemical equiv particles is formed in situ during ‘the process of manu alents and ratios demanded by reactions which develop ?acturing the articles. The present invention is concerned during the stages of heat treatment. Furthermore, the in its principal application with compounds generally re initial forming methods are not con?ned to dry pressing ferred to as hard carbides and hard bor-ides, which term of the molding compositions, but the forming may also is herein used to refer to the carbides ‘and borides of ' be accomplished in the plastic state, and even slip casting metals of-groups IIVB, VB, and Vl-B of the periodic sys— in plaster or paper molds may be had. Also, very high tem (particularly titanium, zirconium, hafnium, thorium, accuracy is obtained in the form and dimensions of the vanadium, columbium, tantalum, chromium, molybde ?nal article produced. num, ‘and tungsten) and in addition thereto, boron. \In accordance with one embodiment of the present in Hard carbides are used as abrasives and in the manu vention, where a dense carbide article is sought, the desired tacture of high speed cutting tools. \At present, a conven carbide as a ?ller and an appropriate quantity of a react— tional method of preparing carbide shapes =for these pur ant constituting an oxide of a metal which forms a hard poses is by bonding the carbide grain with a high melting carbide, are mixed with a suitable quantity of temporary glass or metal or the like. These conventional binders, binder for intially forming the carbide article. if a porous however, have a very low melting point compared with carbide product is desired, a reactant constituting the those of the carbides themselves, and consequently fail metal itself of the above indicated metal oxide is substituted at low temperatures relative to what the carbides them therefor. The binder should be of such composition that selves can withstand. ‘In order to take advantage of the it decomposes to leave a carbon residue on being heated. hard carbide high melting points, the present invention Hard pitch plasticized with tar has been found suitable provides a process for bonding these high temperature ' as a temporary binder for the present process, although carbides with their own or some other similar hard car other binders of the thermoplastic or thermosetting type bide. in this manner a self-bonded or carbide-bonded can be used. After the article is formed and its binder carbide shape is produced free vfrom extraneous binder, has been carbonized, it is of su?icient strength to permit a which may be used at any temperature which the carbides further or iinal shaping by conventional grinding or other themselves can withstand. machining means. Thereafter, the shape is further heat The hard carbides, carbides of the metals above indi treated under controlled conditions to produce, in the case cated, have melting points in excess of 2000" C., some of the oxide reactant, the cxycarbide of both the react-ant even in excess of 3000° 1C., and these high melting points and the carbide ?ller ingredient, which subsequently lib-_ are shared vwith the nitrides and borides of most of the era-tes its oxygen in combination ‘with the carbon binder mentioned metals. Attempts have been made to sinter to leave a sintered carbide article composed essentially these high temperature materials themselves into molded wholly of carbides. ‘In the case of the metal reactant, the articles; however, they oifer considerable resistance to sin heat treatment results in a direct formation of reactant tering, which may be overcome only when heat treated at metal carbide ‘which sinters with the basic carbide ingre temperatures approaching their melting points. The close dients to leave again a sintered carbide-bonded carbide proximity of their sintering temperatures to their melting article composed essentially Wholly of hard carbides. if points and the resultant lack of su?icient temperature desired, a hard :boride ?ller may be used in place of the range between vsintering and melting causes considerable hard carbide to produce a carbide-‘bonded boride. difficulty in such a direct approach, and this dif?culty is In accordance with another embodiment of the present made more severe by the extremely high temperatures in invention, a hard boride ?ller may be mixed with an volved and the poor means presently available for close oxide of a metal capable of forming a hard boride to ‘temperature control and measurement in these ranges. gether with boron carbide as the reactants, and a suitable One process presently employed ‘for sintering hard car temporary binder decomposable on heating to a carbon bide gr-ains is to press form ?nely divided carbide powder residue is also mixed therewith. This mixture is then having intermixed therewith a suitable quantity of an organic binder, such as Oarbowax. The binder is then heat treated in the same manner as for the previously removed by heating, leaving a fragile compact of carbide indicated embodiment to yield products of similar prop which becomes denser and obtains strength as the heating erties. In the instant embodiment however, the oxygen temperature is increased. There are certain disadvantages of the metal oxide combines with the carbon residue of connected with a fabricating method of this type. The the binder and the carbon of the boron carbide to re; method is limited mainly to pressed compacts of very move both elements from the composition, and as a part simple shape. After removal of the wax they become of this reaction the boron from the boron carbide com; very fragile, which is a ‘very undesirable condition in com bines with the metal of the oxide to produce a bOIld€1 2,799,912 3 4 bonded boride article composed essentially wholly of sets into a hard carbonaceous residue which is suffi borides. ciently strong for further ordinary handling, machining, Broadly stated, therefore, the present invention may be or grinding. Further gaseous substances are given off characterized as a process for producing hard carbide up to a temperature of about l000° C.; so for the re or hard boride ceramic articles, wherein as a ?rst stage moval of most of these gaseous constituents it is desir in the production of such articles a hard carbide or boride able to continue the coking about 600° C., at least to ?ller is temporarily bonded by carbon, and then the 700-800" C. The shapes which are thus produced are carbon is reacted with a metal or metals capable of true in dimension and contour. Occasionally, for simpli forming hard carbides or borides or compounds of such iication of molding dies and pressing operations the ?nal a metal or metals so as to form in situ a hard carbide or 10 shape may be developed after coking through grinding boride bond for the ?ller, leaving the ?nal article essen or machining. The articles thus formed are then heat tially wholly composed of hard borides and/or hard treated in the temperature range of 1800—2500° C. to carbides, as the case may be. And in addition, the obtain transformation of the carbon bond into a carbide present invention further contemplates as within its scope or boride by reaction of the carbon with the reactant. the several compositions essential to carrying out the This heating cycle should be as rapid as possible, and processes here indicated to the desired ends. usually lasts from 20 to 30 minutes. It is therefore one object of the present invention to In the fabrication of dense carbide-bonded carbide provide a method of fabrication of carbide- or boride shapes, it is important that maturity be possible at tem bonded articles of carbides or borides. peratures below 2500" C. For this purpose, a ?uxing Another object of the present invention is to provide a reactant is used in the mixture in the form of an oxide; method of manufacturing precision formed hard carbide for example, a molding powder of titanium carbide may articles. contain titanium dioxide as the reactant, or the oxide A further object of the present invention is to provide of another hard carbide forming metal. The hard car~ for the control of the porosity in these carbide shapes, bides, such as titanium carbide, apparently have the ranging from practically Zero to close to 50 percent. ability to absorb oxygen into their crystal lattices in a Another object of the present invention is to provide solid solution of oxide and carbide. These oxycarbides a process for producing boride- or carbide-bonded hard are quite stable even at high temperatures, but are re boride or carbide articles, wherein a carbon binder for duced by carbon to carbide. The oxycarbides apparently the initial hard boride or carbide is formed in an inter develop plastic properties at roughly 20000 C. with a mediate stage of the process of su?icient strength to en 30 fairly extensive plastic range (over several hundred de able machining or grinding if necessary to complete the grees centigrade). This range and the degree of plas shape of the article. ticity is governed by the concentration of oxygen, and Another object of the present invention is to provide the rate of reduction of the oxycarbide to carbide. Both a process for producing boride‘ or carbide-bonded hard these factors are evidently dependent on time and tem boride or carbide articles, wherein a carbon binder for 35 perature, in that a very short heating cycle causes maxi the original carbide or boride is formed in an intermediate mum retention of oxygen at the highest feasible tempera stage of the process and which is subsequently reacted ture and thus causes a maximum of plasticity and con with other constituents of the article to produce the sequent tendency towards shrinkage and high density. If, carbide or boride bond. for example, the temperature is held at 1800” C. for any Another object of the present invention is to provide 40 length of time, the reduction of the oxycarbide proceeds compositions which can be molded and processed in ac slowly, but to a su?icient degree to prevent the develop cordance with methods herein described for the produc ment of a degree of plasticity on heating above this tem tion of shaped boride or carbide articles bonded by car perature as to produce a dense structure. The carbides bides or borides formed in situ. in this process thus become in behavior very similar to Still another object of the present invention is to pro~ ceramic materials of a more conventional type and firing vide a process for producing carbide or boride articles of property, which has the advantage of typing these mate accurate dimensions without need for re?nishing. rials into the established concepts of this industry. It is Other objects and advantages of the present invention apparent that to obtain the oxycarbide, the oxide reactant will become apparent to those skilled in the art from a should present good stability in contact with carbon at consideration of the following detailed description there— relatively low temperatures to prevent oxides of carbon of, given by way of example to more fully explain the from forming prior to the oxycarbide. It is fortunate concepts thereof. that only at high temperatures are the lower oxides of For the purpose of clarity, in the further description polyvalent metals which form hard carbides reduced by here made of the present invention titanium is occa carbon at an appreciable rate, thus facilitating diffusion sionally utilized as a typical example of a metal which of the oxygen into the carbide ?ller. forms a hard carbide. As will become apparent during The amount of metal oxide reactant in the molding the following description of the present process, the mixture is so adjusted that the metal and oxygen con initial molding composition is an important part of the tained therein present the theoretical equivalent neces sary to consume all free carbon in the coked bond of invention, because the end product and the proper func 60 tioning of the process depends to a large measure on the the grain and any graphite that may be otherwise present chemical ratios and reactions of the constituents in the in the article. The reaction products are carbon mon' molding mixture. oxide and reactant metal carbide formed in situ during To form the initial carbide article by dust pressing, the process. It has been found that best results for this reaction are obtained by very rapid heating of the coked a dry ?ne mixture of a binder, as above described, re 65 actant, and the desired carbide or boride filler is used, article, so that the oxygen is not eliminated too rapidly and through the addition of a suitable binder solvent as carbon monoxide before it has had a chance to form the initial article may be formed in a plastic state. By the oxycarbide and cause the desired plastic condition increasing the amount of binder solvent used the article in the article. From numerous experiments it seems like ly that a certain minimum temperature is needed to may be formed by casting. The formed shapes are then 70 subjected to a slow process of heating to set the binder obtain the desired results. The optimum temperature and transform the pitch binder into coke. The pitch range is 2000~2300° C. for titanium carbide ?ller, but being thermoplastic, the formed shape will distort if the varies somewhat with the type of carbide used. By con coking is not done under carefully controlled gradual trast, it may be mentioned that a compact comprising —325 mesh titanium carbide formed without a ?uxing temperature increases. Between about 300 and 600° C. 75 the binder is decomposed, gas and tar is evolved, and it reactant, requires a maturing temperature well in excess arsenic 5 of 25006 C. for the formation of a nearly dense product. gravity of 1.2. A very desirable ?exibility for the ‘ad—' The sintering range is so narrow that melting may occur justment of plasticity results from this combination. due to di?iculties in the control of temperature ceilings. ‘When the pitch and tar mixture is subjected in a When high porosities to nearly 50% are desired, essen pressed carbide or boride compact to a very slow process tially the same processing method is used except that the of heat treatment or coking, tar vapor and gas are given bonding carbide is formed in situ either entirely or partly olf. The pitch becomes plastic, but as the temperature from free metal powder, such as titanium, and carbon. increases and decomposition progresses, the plasticity de The formation of the carbide in the present instance ap creases until at about 500° C. a solid residue is left which pears to begin at temperatures of about 700° C. and in~ is still rich in gaseous constituents. These can be elimi creases in velocity as the temperature is increased. A 10 nated by further heating to 900—1000° C., but for most considerable amount of heat is thereby developed which purposes heating to about 750° C. is su?icient. When is su?icient to cause the reaction to become self-accelerat molded [carbide or boride compacts are coked, a de?nite ing in a very violent manner under a temperature rise heating schedule must be maintained, and the increase in which may exceed 2000° C. within a few seconds. In temperature must be slow enough to prevent deforma several instances, a temperature of 2300" C. was meas 15 tion or bloating; A 25° C. increase per hour up to ured with an optical pyrometer. This heat can be used '500-600" C. has been found satisfactory for most pur for curing these compacts, but a disadvantage of this poses. Once above this temperature range, a higher rate method of curing is the occurrence of some variation in of vincrease, for instance 50° C. per hour, may be main~ uniformity of the product. Where a high uniformity in tained. Large shapes must be heated more slowly than pore structure, pore volume, or density of product is 20 small ones, ‘because the gases have to travel a longer desired, a technique is followed which conforms very distance to reach the surface. This coking is best accom closely to that used in coking; that is, by continuing a plished in an electric muf?e furnace, a crucible, or a slow temperature rise as used during the coking period steel tube in an inert or reducing atmosphere, to prevent to approximately 1300” C., a slow and smooth reaction oxidation of the bond. takes place between reactant metal and carbon. At that 25 The equipment for molding is of conventional design. temperature, the reaction is not entirely complete, but The press should be ?tted with a heavy vibrator of sul? is su?’iciently advanced to prevent a further violent tem cient force to be effective at a pressure of about 5 tons perature increase. The compacts thus prepared may be per square inch. The pressure may be increased further ?rst ground to dimension after coking, but are further up to about 20-30 tons if necessary. Molding in plastic treated by heating in an induction furnace or the like to 30 or liquid condition also follows essentially conventional l800-2500° C. An addition of silicon may be made in lines. The molding composition is the same as described the initial molding composition, which increases the for dry pressing, but an added amount of solvent imparts strength of the compact at lower temperatures (1300“ C.) further plasticity or ?uidity. After forming, the solvent and increases the porosity when itis vaporized out at is evaporated slowly in much the same manner as water high temperatures. is left to evaporate from conventional ceramic compo The following discussion clearly illustrates the details sitions. When forming by slip casting is undertaken, the by which the present process for fabrication of shaped amount of pitch has to be larger than usual to compen carbide-bonded carbide or boride articles may be satis sate for the amount of pitch which is carried by the factorily carried out. It is very important that the initial solvent into the mold.‘ The initial porosity of cast or molding mixture be very homogeneous to prevent the 40 plastic formed specimens is somewhat higher than those formation of strains and other defects in the ?nal product. produced by dry pressing, but after drying may be sub A combination of mixing steps has shown satisfactory jected to the same coking and further heat treatment. results. The dry powdered materials comprising the In many cases, the carbide compacts can be molded molding composition of carbide or boride ?ller, reactant, to the desired shape, and dimensions by allowing for and temporary binder are ?rst mixed in dry condition, 45 shrinkage. There is practically no shrinkage in the proc then put through a micropulverizer to break up agglomer ess of coking, but there is usually considerable shrinkage ated particles, as are sometimes found in the oxide con during the subsequent ?ring step at high temperatures. stituents or in the pitch. Then tar and solvent are added Where the contours of the shape are complicated, it is and the resultant slurry thoroughly agitated to dissolve desirable to con?ne the original molding to simpler form and distribute the tar and pitch. Examples of such sol 50 and then coke the shape and subsequently give it the ?nal vents are toluene, xylene, etc. The ingredients can also for_m__ by machining and grinding. The coked shapes be hot mixed in a pan type mixer ?tted with heavy have the strength and the necessary properties for this mullers if the batch is large enough for such an operation. operation. By careful determination of the shrinkage In hot mixing, the amount of solvent can be eliminated and by allowing ,forit, tolerances as high as 1.002 inch or kept at a minimum. After thorough mixing, the were consistently obtained in some cases. This accuracy solvent is evaporated, and on cooling leaves a mass con is unusual for ceramic methods, but it is very important sisting of hard granules which are pulverized in a hammer as grinding of dense carbide or boride articles would not mill to a ?ne powder passing a l00-mesh screen. The only be expensive but diamond tools would have to be powder thus produced is then ready for molding. used, and these have a strategic value in the event this The powder lends itself to both dry pressing and hot 60 country is cut o? from supplies of diamonds abroad. pressing operations, though cold molding is preferred The accuracy and consistency of results of the fabricating Whenever possible as the technique is simpler. It has method accomplishes one of the important objects of the invention. ' been found, however, that evacuation of the mold before In the formation of dense articles, the further heat pressing is of considerable importance in preventing the 65 treatment after coking is carried out by any method that formation of laminations and closed pores, and that the permits very rapid heating in an atmosphere that will not application of vibration during pressing results in im contaminate the product, as for example, in an atmos proved homogeneity and the elimination of spongy sec phereof .carbon monoxide, hydrogen, helium or argon. tions in the center. In many instances, carbon monoxide in a graphite As a binder, a grade of pitch should be employed 70 crucible will be found satisfactory. This heat treatment which is hard enough to be pulverized in a hammer mill can be accomplished very readily in an induction furnace to a ?ne powder. A suitable pitch for this purpose has ?tted with a carbon crucible and insulated with carbon a melting point of about 300° F. This material lacks black in a manner which _is standard for this type of the necessary plasticity for cold pressing and is for this . work. By suitablechoice of conditions, a very rapid reason plasticized with water free coal tar of a speci?c heating to about 2500° .C. .can be accomplished in 20-30 2,799,912 77 minutes, or even less. This rapid temperature increase For the purpose of determining the proper ratios of may be followed by a period of soaking, ‘but in most ~ components of the initial composition, the yield of car instances, this soaking period is of less importance than bon from pitch and coke averages 40 percent, to which the rapid passing into the temperature range above about must be added the quantity of graphite which the carbide 1800° C. in the case of producing articles of high 5 contains. This percentage of graphite in a rather pure porosity Where a metal instead of a metal oxide reactant carbide is about 1.5 percent, but it may be higher in some is employed, as previously indicated the ?ring should be cases, and may be as high as 3.25 percent, as in the case carried out under conditions of gradual temperature rise of titanium carbide. The total free carbon is then re (25° _per hour) 1%) tlccli 1310f? C. before proceeding by 10 lated to‘ tfhe1 equivalent quantity of oxide in accordance a mp1 increase to t e na ring tempera ure. witi tne oi owing equation: It will be understood that certain variations in proc~ heat essing conditions are necessary to adjust the process to Ti0i+3C —-—> 200+Ti0 changes In COIT‘POS‘QOHR howe‘ier’ one skllled m the art An analytical check on the content of carbon in the end will have no dl?'lCIlllIlCS. in . making such adjustments.. . ,. product, and corresponding. adjustments, in. the content The following. . table gives examplesof. combinations 1-) of oxide_. or in. the choice. of_ the oxide. provide. a simple,. of materials. which .respond well to this process. for pro-. means of controlling. the initial. . . composition.. . ducing dense. carbide-bonded hard . carbide. or boride rioni.1 tne. aoove, examplesH it- can be seen that mixed.‘ shaped. . articles.a . Many of these combinations. can be con- carbides, - can, be produced_ by use oia a carbide- ?ller with, - sidered. n as. equivalents. for purposes. of this . process, and an oxide,- reactant of a different.- metal. It will- also -be their_ carbides or bcrides and oxides. can be interchanged.. . 20 seen that the carbides- oi_ borides- when bonded with- car Furthcrmore,. some of, the carbides. form solid solutions. b on and treated with-_ boron oxide- vapor (whicht may be with each other, so that also mixtures of carbides can > b h l- f n h "n 1 h- h be‘ used in the process carried y e ium) o. ow t e genera pattern _w it: ' gives the process a broad ?eld of utility. A variation of Filler Mate,m1 carbonized Oxide 25 the process is,_for example, the bondinglof a hard boride, Bond such as titanium, zirconium, or hafnium boride, with carbon in the presence of boron and zirconium oxide. g gig: In an intermediate stage, boron carbide is formed, which C’, “a6! at high temperatures is oxidized by the zirconium oxide 8 $106 30 while zirconium boride forms. If desired, this variation 0 T323,‘ may also be carried out using boron carbide in the initial 8 ,lM‘igoi molding mixture rather than boron metal, thus eliminat C v20: ing the intermediate reaction to produce boron carbide. g E381 The following is an example of an initial molding com 0' 13,6, 35 position in approximate parts by weight for the latter 8 1 gig! instance: 2 3 Parts 1Vapor in He. 9' ______““ 1170(1) The following examples of initial molding compositions 40 mg 3525 give a number of formulae in approximate parts by Tar ______10 weight7 for providing the dense articles: For producing_ less dense grains,_ in_ place of the oxide, 1‘ IJYC ——————————————————————————————————— —— 75-8 reactant, for example TiOz, the corresponding metal pow Pltch —————————————————————————————————— —- 65 der can be used to absorb the bonding carbon by forming $116 ——————————————————————————————————— — ‘15 TiC. The following example is an illustration thereof: 1 2 ______.. . 2 ZrC 116 Parts Pitch """""""""""""""""""""""""""""" " 10 10. TiC ______85 Tar """"""""""""""""""""""""" " 5 Pitch ______9 """""""""""""""""""""""""" "' Tar _~______.______7 zro»“ ______21 50 Ti. ______24 3 ------3;; (_200 mesh)

1 2 ______. . . . Pitch ______10 The following example shows the fabrication of highly Tar _ I;“:““':_:_:_::_:___:_:_: ______5 porous carbide shapes from merely a metal powder re 4 TC — ' _ _ _ ~- 85 55 actant and carbon: T10 """""""""""""""""""""""""""""" "' 24 Parts { i ------" 10 11. Titanium powder, —-200 mesh ______-_ 80 inc “““““““““““““““““““““““““““““““ “' 5 Powdered petroleum coke, degassed at 1000° C., ar ------" -200 mesh ______14 5 TaC ------225 60 Pitch, M. P. 300° F ______10 TDIOZ ------—— Coal tar, water free, sp. gr. 1.2 ______10 """""""""""""""""""""""""" "_ 5 The ingredients are intimately mixed with the help of a ‘ ______“ 97 solvent, such as toluene as previously described, and then 6 c ------" 22 65 formed. The molded shapes are coked and gradually n02 ------" 10 heated to about 1300° C. in an inert or reducing atmos Pltch ------r- 5 phere. The rate of heating is about 25° C. per hour Tar ------" throughout this heating cycle, but may be varied so long 7 TaC ------225 as the spontaneous reaction is not precipitated. At the T8205 ------—- 32 70 indicated rate of heating the dissipation of the heat of Pitch —————————————————————————————————— —— 10 reaction during carbide formation is faster than the gen Tar ______-~ 5 eration of this heat and the self-accelerating explosive 8 VC ______97 nature of the reaction remains checked. After this first V203 ______.._ 25 heating cycle, the compacts are heated to about 1800” Pitch ______. 10 75 C. to 2500° C. to diffuse the metal and carbon completely Tar ______5 - and produce full homogeneity. The rate of heating in 2,799,912 10 this case is not greatly important, although it may be thorium, vanadium, columbium, tantalum, chromium, just as fast as previously described. The shrinkage of molybdenum, and tungsten with a metal oxide of one of the compacts is slight. Other metals besides titanium, said group metals as a reactant and a carbonaceous tem or mixtures of metals may be used. porary binder carbonizable in the range of 600—800° C., In instances it may be desired to employ the teachings micropulverizing the dry mixture, mixing tar and a sol of the present process wherein the carbon content of the vent for said tar and carbonaceous binder with said dry ?ller may be excessive, so as to preclude the use of a mixture to dissolve said tar and binder throughout the carbonaceous temporary binder. In such instance a non mixture, evaporating said solvent from the mixture, pul carbonaceous temporary binder may be employed, such verizing the mixture of said ?ller, reactant, and binder in as zirconium oxychloride. The hard boride or carbide a dry state to pass a IOU-mesh screen, plasticizing said ?ller is mixed with the zirconium oxychloride and heat mixture to a suitable viscosity for slip casting, slip cast treated in the same manner as the previous examples to ing the plasticized mixture to a desired shape, slowly heat provide a zirconium carbide bonded hard carbide or ing the cast shape at 25° C. temperature rise per hour to boride. In this case the binder also acts as the reactant approximately 500° C. and then at a 50° C. rise per hour and the molar quantity thereof in the mixture is chosen 15 to 600-800" C. to carbonize said binder and harden the, to substantially exactly consume the carbon of the ?ller shape for handling and machining, cooling said hardened in accordance with the following equations: shape, machining said shape by conventional means to a desired ?nal shape, and heat treating the ?nal shape to approximately 1800-2500° C. in 20 to 30 minutes in an 20 heat inert atmosphere to react the constituents of said ?nal ZrO; + 30 —> ZrC + 200 shape to form carbides and borides of said group bonded There is thus presented a process for manufacturing to the carbide of the metal of said oxide. carbide-bonded or boride-bonded shaped hard carbide 0r 2. A process for fabrication of shaped boride-bonded boride articles by forming said bond in a shaped compact articles comprising dry mixing a powder ?ller chosen of the ?ller through chemical reaction of appropriate in 25 from the borides of the group consisting of titanium, zir gredients incorporated in the compact in proper chemical conium, hafnium, thorium, vanadium, columbium, tanta equivalents to substantially completely react in forming lum, chromium, molybdenum, and tungsten with a powder the bond, said ingredients being further chosen so that metal oxide of one of said group metal as a reactant and a any other products of the reaction are readily removed carbonaceous temporary binder carbonizable in the range from the compact, as for example gaseous products. of GOO-800° C.; mixing tar and a solvent for the tar with Furthermore, this process enables the production of these the ?ller, reactant, and binder; removing the solvent from articles with a high degree of dimensional accuracy and the mixture; pulverizing the mixture; forming a desired reducibility, and further enables the production of these shape from the pulverized t-ar, ?ller, reactant, and binder; slowly heating the shape at 25° C. temperature rise per articles with various and reproducible densities or porosi~ 35 ties, as desired. In addition, the present invention pro hour to approximately 500° C. and then at 50° C. rise per vides various molding compositions appropriate for e?ect hours to 600—800° C. to carbonize said binder and harden ing the process. The detailed embodiment of the process the shape for handling and machining; and heat treating and the various detailed examples of the molding composi the shape to 1800-2500“ C. in 20 to 30 minutes in an inert atmosphere to react the constituents of said shape tions hereinabove stated are presented merely by way of 40 example to enable a clear understanding of the present to form borides of said group metals bonded to the boride invention. Therefore, modi?cations of the teachings, of the metal of said oxides. stated herein, as will be apparent to those skilled in the art, which are within the spirit and scope of the invention References Cited in the ?le of this patent as de?ned by the appended claims are within the con 45 UNITED STATES PATENTS templation of the present patent. 2,109,246 Boyer et al. ______Feb. 22, 1938 The invention described herein may be manufactured 2,141,617 Ridgway ______Dec. 27, 1938 and used by or for the Government of the United States 2,228,871 De Bats ______Jan. 14, 1941. of America for governmental purposes without the pay ment of any royalties thereon or therefor. 50 FOREIGN PATENTS What is claimed is: 491,659 Great Britain ______Sept. 6, 1938 1. A process for fabrication of shaped carbide-bonded 570,805 Great Britain ______July 24, 1945 and boride-bonded carbide articles comprising dry mixing 580,963 Great Britain ______Sept. 26, 1946 a powder ?ller chosen from the carbides and borides of 640,497 Great Britain ______July 19, 1950 the group consisting of titanium, zirconium, hafnium, 55