CA1157606A - Methods of manufacturing gradient composite metallic structures and gradient composite metallic products - Google Patents
Methods of manufacturing gradient composite metallic structures and gradient composite metallic productsInfo
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- CA1157606A CA1157606A CA000394430A CA394430A CA1157606A CA 1157606 A CA1157606 A CA 1157606A CA 000394430 A CA000394430 A CA 000394430A CA 394430 A CA394430 A CA 394430A CA 1157606 A CA1157606 A CA 1157606A
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Abstract
ABSTRACT OF THE INVENTION
A rolling cutter drill bit is disclosed having cutters manufactured by powder metallurgy techniques, said cutters hav-ing gradient composite metallic structures in the cutting areas arranged to reduce or eliminate physical and metallic disconti-nuities and stress risers.
A rolling cutter drill bit is disclosed having cutters manufactured by powder metallurgy techniques, said cutters hav-ing gradient composite metallic structures in the cutting areas arranged to reduce or eliminate physical and metallic disconti-nuities and stress risers.
Description
~57606 METHODS OF MANUFACTURING
GRADIENT COMPOSITE METALLIC
STRUCTURES AND GRADIENT
COMPOSITE METALLIC PRODUCTS
~ACKGROUND OF THE INVENTION
The present invention generally relates to drilling bits utilized in the oil well drilling industry and in the min-ing arts, and more particularly involves a uni~ue metallic com-position for the cutting elements utilized in drilling bits.
In the conventional drill bit technology, there are generally two kinds of rolling cutter drill bits, as well as what is termed drag bits having no rolling elements. The rolling cutter drill bits are generally of the type having cantilevered frusto-conical cutters such as the tri-cone bit, and there are additionally bits having cutters mounted transversly on axles supported at each end by saddles, which in turn are affixed to large cutting heads. This second type of rolling cutter bit primarily is used in the mining and tunneling industries. In the tri-cone rolling cutter type of bit, there are generally two kinds of cutter struc-tures utilized, the "milled tooth" cutter, and the insert cutter.
In the milled tooth cutter, a large forqing is milled away, leav-ing protruding, sharp, wide chisel-shaped teeth as the cutting elements. These projecting teeth may have a hard material, such as tungsten carbide, welded to their faces to increase their ero-sion resistance. The cutter bodies themselves may be carburized and hardened to increase their resistance to breakage and wear.
In addition to the milled tooth cutters, rolling cutter drill bits commonly utilize insert type cutters wherein a smaller original cutter body is utilized with a minimum amount of machin-ing, and holes are drilled circumferentially around ~he cutter body to receive hard metal cutting inserts which are pressed there--` llS7~06 into. These hard metal inserts generally are formed of a tungs-ten carbide composite made in a generally cylindrical shape with a pointed protruding portion. The insert type cutter bodies generally are carburized and hardened prior to insertion of the inserts.
In the mining industry, the saddle type cutters most often used are the milled tooth variety, although the insert type cutters are becoming more widely used. The formation of these cutters is similar to that as described above with respect to the tri-cone drilling bit cutters. In the formation of the rol-ling cone cutting structures utilized both in the tri-cone bits and the mining bits, the two types of cutters can generally be classified as utilizing both gradient techniques and composite techniques, although none of the conventional cutters have com-bined these two techniques to arrive at a gradient composite me-tallic structure.
The term "composite" is used in the microstructural sense herein, as is commonly known in the fields of metallurgy and materials science. It refers to materials having micro- ~;
structures composed of at least two individual phases, the ;
volume fraction of a minor phase being at least 10~, which are bonded together in such a manner that the average properties of the composite are determined by the individual properties and morphology of each phase. This usage is distinct from that where an engineering structure may be referred to as a "composite" when it is comprised of two or more distinct, relatively large regions, bonded, coated, welded, or otherwise joined or internally transformed, forming a heterogeneous unit.
See--THE PRINCIPLES OF ENGINEERING MATERIALS, Barrett, Nix and Tetelman, Prentice-Hall, Inc., 1973, pp. 316 - 317--.
' ~L~57606 For e~a~ple, both the milled tooth cutter and the insert type cutter utilize the composite structures in that they both have a steel alloy cutter body to which is added a hard metal cutting surface, or cutting element. In the milled tooth S cutter the composite hard metal element is added as a tungsten carbide alloy weldment which is fused to the cutting surfaces on the teeth, the gage, and portions of the cutter body. In the insert type cutter, the composite element is added by the inser-tion of the cemented carbide insert into the alloy steel cutter shell. The result of these two types of composite metallurgical construction is a "metallurgical notch", where a very sharp gra-dient is formed across the interface between the hard metal and the alloy steel. In addition to this metallurgical notch, or discontinuity, the composite formed thereby also suf~ers from a disadvantage in that a geometrical notch is also usually formed at the juncture. These metallurgical and geometrical notches serve to weaken the resulting composite metal component and con-tribute to earlier failure of the cutting structure. These discontinuities in elastic moduli, coefficients of thermal ex-pansion, and yield characteristics limit drilling performance by affecting the residual stress distributions and applied stress distributions in service. These characteristics and changes re-~
sult from all of the different techniques which have been uti-lized in conventional cutter construction for xeducing deforma-tion and improving wear-resistant qualities on drilling equip-ment.
The composites utilized in conventional cutters have increased the mechanical strength, toughness and hardness but have not efficiently optimized these characteristics for drill-ing equipment. In addition to the welding of hard metal, such ~ as cemented carbides, on the cutting structures, other conven-;' .
~57606 tional techniques have involved brazing of the cemented carbides, plasma spraying of cemented carbide coatings, and chemical and electrical deposition of coatings having high carbide fractions.
All of these techniques suffer from the above-mentioned mechani-cal and metallurgical discontinuities at the joint interface.
Likewise, the insert cutter construction has been utilized to improve the mechanical strength, toughness and wear resistance of the cutting structure, but it still suffers from the elastic strain requirements of the interference fits, in addition to the limitations of the steel-composite interface on load bearing abi-lity.
The use of mechanical property gradients in convention-al drilling tools has been known and accepted for many years.
For example, gradients are introduced into the cutting structures by the case hardening, carburizing treatment of steels. The re-sultant gradient of a carburized case-hardened steel comprises a hard brittle outer surface shell with a tapering-off of the hardness and increase in toughness towards the interior of the part. This has been successful in reducing gaLling and spalling of bearing surfaces and other high unit loading contact areas, ~; but offers little improvement to erosion resistance which is preva-lent in rock drilling. Also, this type of gradient is generally relatively shallow, usually extending no more than 0~050 inches into the steel component, thus subjecting the surface to crack-ing or failure by plastic deformation. Other types of mechani-cal property gradient-producing processes include laser and in-duction hardening, nitriding and boronizing.
The present invention overcomes these disadvantages and provides an optimum cutting structure by the use of gradual or continuous gradients across the geometry of the cutting .
- ~57606 structure. This continuous or gradual gradient substantiall~
eliminates the interface and the resultant geometrical and meta-llurgical notches found in the conventional cutter construction.
The elimination of the discontinuities may involve varying seve-S ral different parameters to achieve different desirable techniques.
For instance, the composition, the fraction, the shape, the size and the distribution of phases in a cemented carbide composite may be systematically varied by powder metallurgy techniques to produce an insert with continuously varying properties. The gradient through the insert can be arranged so that a hard, stiff, abrasion-resistant cemented carbide structure exists at the tip of the insert, merging into a tougher, softer cemented carbide structure in the regions of high bending stress lower in the in-sert body. The gradient across the inserts can also ~e arranged such that when fused to the normal alloy steel cutter shell, the attachment surface of the insert can be substantially of the same composition as that of the alloy steel cutter shell so that the added insert becomes an integral part of the cutting struc-ture as though originally formed therewith, and a hard metal core extends downwardly along the central longitudinal axis of the insert.
In a second embodiment of the invention, the cutting structure is formed in a single operation rather than by the addition of inserts to a cutter shell. In this embodiment, the cutter and the teeth structure are formed in a single manufac-turing operation utilizing powder metallurgy techniques. A pro-grammable mixing system for mixing the alloying components of '~ a powdered metal alloy serves to place the proper concentrates of the cemented carbides in the locations requiring the proper-ties of cemented carbides and gradually reducing the cemented carbide fraction as you move geometrically away from these criti-cal points. The resulting cutting structure therefore has con-centrated fractions of cemented carbide in the high-stress, high-erosion areas with a gradual decrease in the hard metal component away from these critical areas towards the body of the cutter. The alloyed ~owder metallurgy components are then densi-fied into a single integral cutting structure utilizing conven-tional powder metallurgy techniques, such as hot isostatic press-ing. Then the completed cutter is removed from the pressing die and minor machining operations can be performed to create smooth bearing surfaces and seal surfaces within the cutter where required. Thus, it can be seen that the resulting drilling bit cutter offers an optimum metallurgical cutting structure in that it utilizes the desirable effects of the composites, such as ce- .
mented carbides, in the locations on the cutter wher~ such char-acteristics are desirable, and the desirable characteristics of a tough resilient core, such as the alloy steels, for strength and foundation in the cutter shel- itself with a smooth continu-ous gradient between the cemented carbide and the alloy steel to greatly reduce or eliminate discontinuities and their resul-tant stress risers. In addition, the locations of the gradientsand the gradient rates can be manipulated to provide favorable compressive residual stress patterns in a finished component, thereby raising the effective fracture resistance o~ the result-ing cutting structure.
Thus broadly, the invention contemplates.a ~owder met-allurgical method of constructing a cutter for a rolling cutter drill bit which comprises providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy, providing a second powder comprising a powdered binder metal or alloy or a mix-ture comprising a powdered refractory material and a powdered binde.r metal or alloy, present in a lesser proportion ~,~ by volume than in the first powder, forming the ~ 57606 cutter of the first and the second powders, mixing the powders while forming the cutter and introducing into a first region of the cutter a mixture having a first pre-selected proportion of the first powder relative to the second powder, and changing the relative proportions of the powders while mixing to introduce into a second region of the cutter a mixture having a second preselected proportion of the first powder relative to the second powder and a continuous gradient in the relative proportions of the powders between the regions. The powders are then densified into a solid cutter having a gradient in composition and properties from the first region to the second region.
The invention also includes the cutter product of the inventive method for rock cutting tools and the cutter includes a body which comprises an exterior cutter surface region having cutting means thereon, an interior cavity having bearing surface means there}n, and the cutter body having a portion of substantial thickness comprising a densified powder metallurgical composite of at least two varying phases, which has a substantially continuous mechanical property gradient through the body portion.
In another embodiment the invention includes a cut-ting element for attachment to a rolling cutter which is rotatably mounted on a drill bit and that cuttlng element comprises a root portion adapted for engagement in a bit cutter, a cutting portion on the root portion adapted to protrude from a bit cutter in a cutting orientation, and wherein the cutting element comprises a portion o~ substantial thickness comprising a densified powder metallurgical composite of at least two vary- -ing phases, with the composite having a substantially continuous mechanical property gradient through the cutting portion.
-6a-': :
~L157606 In a further embodiment the invention contemplates an insert for use in an insert-type rolling cutter drill bit which comprises a geometric base portion for insertion into a matching hole in a drill bit cutter, a tapered, geometrical cutter portion formed on the base portion and adapted to protrude from ~ ~ole in a drill bit cutter with the insert cutter por*ion comprising a densified powder metallurgical composite of at least two varying phases, and with the com-posite having one portion in which one phase is present in a large volume fraction relative to the other phase, another por-tion in which the other phase is present in larger volume fraction relative to the one phase and having a substantially continuous mechanical property gradient therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
:
Figure 1 is a schematic drawing illustrating one e~cdi-ment of the powder mixing process. Figure 2 is a cross-sectional schematic drawing illustrating the apparatus for manufacturing _a powdered metal cutter. Figure 3 is a partial cross-sectional drawing illustrating a rolling cutter manufactured by the pro-~.
-6b-~57606 cess of Figures 1 and 2. ~igures 4, 5 and 6 illustrat~ cross-sectional partial views of dlfferent embodiments of the present invention utilized in intcgral tooth cutters. Figures 7 and 8 illustrate partial cross-sectional views of inserts l,lade accord-ing to the present invention. Figures 9-11 illustrate graphi-cally the relationship between powder feed rates and time.
Figure 9 appears with Figure 1.
DESCRIPTION OF THE PREFERRED E~BODI~lE~TS
Referring now to Figure 1, which illustrates a sche-LO matic diagram indicating one particular method of forming the gradient composite metal structures of the present invention, a plurality of powder supply bins feed powder through a closely controlled auger system into a mixing chamber fro~ ~w~ence it flows into a rotating die. In this embodiment, a primary supply bin L5 10 is supplied with a powdered metal A having a high percent car-bide fraction. A secondary supply bin 11 is provided with a powdered metal 8 having a low percent carbide fraction, and a tertiary supply bin 12 is supplied with a powdered metal C com-prising a steel alloy havinc superior bearing qualities. Pri- ``
'0 mary bin 10 is provided with a funnel-shaped wall 13 feeding through a section 14 into a screw auger tube 15. A rotating screw 16 is rotatably located in channel 15 to accurately dis-pense powder A into the mixing chamber 17. The feed auger 16 is preferably microprocessor-controlled to precisely discharge controlled amounts of powder A at variable rates into chamber 17. LiXewise, secondary bin 11 has a funnel-shaped wall section 18 feeding into a narrowed throat section 19 and thence into auger tube 20 having screw auger 21 rotatably mounted therein and tightly controlled by a second microprocessor circuit (not shown). Tertiary bin 12 has a funnel-shaFed wall section 22, throat section 23, screw auger tube 24, and feed auger 25, which ~ 57606 is also mic-o?rocessor-co~t-olled or ~recisc moterin~ of ~ow-dercd metal C into mi.~ing chamber 17. Po~der dispensed in mi~-ing chamber 17 flo~s through a vibratable discharse chute 26 into a rotating die 27 whenceforth it is moved by centrifu~al force out~ard into the outer cavities of die 27. ~ vibrator 48 is lo-cated on chute 26 to facilitate thc flow of powder therethrough.
Figure 9 illustrates a schematic graph showing the feed rates of the various powders A, B and C into die 27 in a typical pro-cess embodying the present invention. The vertical axis of the Figure 9 graph represents the rate of powder flow into the mix-i~g c~am~er 17and the horizontal axis indicates the time continuum.
It can be seen from Figure 9 that by means of the microprocessor system ~not shown), which system is well known in the art, the volume of powder flow initially is heavy in componen~ A and light in component B, with no co~ponent C being introduced. The vol-ume feed rate of component A decreases with time at about the ; same rate component B increases with time until a point where component B peaks out slightly before component A is completely shut off, Component B then begins to decrease in volume feed ~ 20 rate, and at the time component A is terminated, component C
i begins feeding into chamber 17. Component B decreases to a point where only component C is being introduced into the rotating die ; and component C is introduced therein until the die cavity is completely filled.
By the use of the present system, the high percent car-bide fraction A ends up in the outer extremities and surface por-tions of the product being formed in the rotating die 27. Then moving inward towards the inner portion of the comoonent being built, the percent of high carbide fraction cornponent A gradu-ally reduces as the percent of co~ponent B increases, resulting in a gradual continuum of hish carbide fraction to low carbide ~.157606 fraction. Then towards the inner portion and center of the co~-ponent is the final component C comprising a powdered metal of an alloy steel having superiar bearing surface qualities.
It should be noted that, in powder metallurgy processes, the powdered metal constituents of the part being manufactured must be compressed to remove the gas voids and heated to solidify and strengthen the part. Thls is normally done in one of several ways. One method uses a pre-compaction of the powder into a "green" part and then sintering at a temperature above the liquidus temperature to fuse the powder. The sintering usually occurs in a vacuum or inert gas atmosphere. An alternative process comprises Hot Isostatic Pressing, commonly termed, "HIPing".
Other processes such as hot forging are also used. ~or conven-ience, all such processes will be occasionally referred to here-in as "densification".
Referring now to Figure 2, the rotating die 27 is illustrated in close-up cross-sectional view. The inner configu-ration of die 27 is adapted for manufacturing a typical integral tooth rolling cutter for a tri-cone drilling bit. In this par-ticular embodiment r die 27 comprises a tough metal outer shell 28 made of a material such as steel and a disoosable material 29, such as castable ceramic, molded by a conventional process such as a lost-wax or investment casting process. Ceramic materi-al 29 is formed in the shell 28 with an internal cavity 30 shaped to correspond to the external dimensions of an integral tooth cutter body for use in the aforementioned drilling bit. This cavity generally has a body section 31 which has radially out-wardly projecting tooth sections 32. Above the cutter cavity is a generally cylindrical filler neck 33 with a funnel-shaped top 34. During the powder-filling stage of forming the cutter, ~: .
;7606 powdcr ~ is first fed in~o the rotatincJ die 7 SuC~l that it ~or~s around thc surface of thc teeth and cutter body as indic~tcd at 35. The distribution of po~dcred metal along the irregular surfAce of the die cavitr may be controllcd by the rotary die speed, oricntaticn of the die rotational axis with respect to the vertical, and/or the geometric configura~ion of discharge chute 26. This configuration may be selected to provide a stream of any desirable width or may be adapted to produce a uniform or non-uniform "curtain" of powder. Powder A is heavy in the cemented carbide component of the final cutter metallurgical content. Because of the rich feed rate of component ~ during the initial filling of cavity 30, the outer extremities of cavi-ty 30, such as indicated at 35, have an extremely high percen-tage content of the cemented carbide component movin~ inwardly from the outer surface of the cavity. A gradually decreasing amount of cemented carbide and increasing amount of matrix ma-terial is encountered in the area 36. This corresponds to the decreasing feed rate of component A and the increasing feed rate of component B, as shown in Figure 7. Near the center of cavity 30 is relatively pure component C corresponding to the far right-hand portion of the graph in Fig~.re ~. This is indicated at 37 in Figure 2. A phantom line 38 is disclosed showing the desired final outline of the internal portion of the cutter after it has been densified into the final product, and machined to create internal bearing areas.
After the varying gradients of the powdered metals have been added to cavity 3C, the die shell is closed by steel cap 40 which is welded across the top, and the gas content is evacu-ated through pipe 50. The die is then placed in a HIPing cha~-ber where a pressurized inert gas such as argon is introduced.
The hydrostatic pressure of the inert gas is increased and the ~ ~.57606 temperature in the chamber is simultaneously increased untll cap 40 is deformed inwardly. The powdered metal is thus comp-ressed radially outward into cavity 30 to form the final sintered metal par~ having the external shape shown in Figure 3. A ter a sufficient period of time, pressure, and temperature to com-pletely solidify the powdered metal in cavity 30, cap 40 is re-moved and the ceramic material 29 is fractured to remove the c~m-pleted, solidified cutter.
Referring to Figure 3, the cutter 41 is shown after removal from the centrifugal die. Cutter 41 may then be machined to provide bearing surfaces 42 and 43 and a seal cavity 44.
Cutter 41 in its final state is a single integral body member having protruding teeth 45, with the body 41 and teeth 45 exhibi-ting a gradual metallurgical gradient beginning with a high tungsten carbide surface and thickness 46, and ending in a low carbide, high steel bearing area 47 for superior bearing surfaces 42 and 43. The gradient from the extremely high carbide content area 46 to the-extremely low carbide content 47 is almost uniform and gradual across this thickness. This resulting cutter has no metal-lurgical notches, as mentioned wlth respect to the prior art, and as a result, offers extreme hardness and erosion resistance at the outer surfaces and along the cutting members 45 while the inner area 47 provides extreme toughness and hardenable surface material for bearings and seals. Also, the cutter exhibits a surface greatly freed of pores and defects.
Referring now to Figures 4 through 6, various construc-tions for cutter teeth are disclosed in broken-out, partial cross-sectional illustrations. Figure 4 illustrates the teeth 32 as shown in Figures 2 and 3. In tooth 32, the entire outer ~ ~ 57606 surface comprises the tungsten carbide-ric~ component ~ with a gradual decrease in carbide in area B and a relatively pure alloy steel in area C. Although tooth 32 is disclosed as part of the integral cutter member 41, an alternate method of manu-facturing cutter 41 is to form the teeth in a separate operation.
Each tooth could be precompacted in green form utilizing powder metallurgy techniques, and then inserted into their proper cavi-ties in die 27. Then the remainder of powder to form the cutter body is added to the die and the entire cutter is then densified by Hot Isostatic Pressing. Alternatively, the teeth and cutter can be densified separately and then fused together by means such as electron beam welding.
Figure 5 illustrates a different gradient ~oncept em-bodied in a tooth member 132. In this embodiment, a carbide-rich fraction A is disclosed running longitudinally through the center of a tooth member 132 and do~nward into the root section 133.
The rich carbide section comprises a generally planar shape run-ning transversely through tooth member 132. A gradient is es-tablis~ed with material B on both sides of the carbide-rich plane A. The remainder of root section 133 is made up of primarlly steel C. The high-modulus core of this structure is particular-ly adapted to carry drilling stress into the cutter bodv by an internal route rather than across defect-prone surfaces.
Figure 6 illustrates in a broken-out, partial cross-sectional isometric view a third embodiment 232 of cutting teeth for cutter body 41. In tooth 232, a carbide-rich area is formed along the sur~ace of the tooth and the root section, and also a carbide-rich area is formed down through the center of the tooth in a planar shape similar to that of ~igure 5. Actually, the cutting tooth 232 is a combination of the structures 32 and 132.
~1~7606 ~he remainder of the tooth and a portion of the root section 233 comprise the mi~ed component B, and the rcmainder of root por-tion 233 is made up of pure steel alloy C. As previously men-tioned, manufacturing techniques to form the cutting teeth 32, 132 and 232 can be utilized in the process of Figure 1 to form an integral cutter assembly or alternatively, the individual cutting teeth may be formed separately in a gradient forming process and then densified as a unit with the body or may be separately densified and then added to the cutter body prefer-ably along isopleths of composition by means such as welding or fusion.
A~though not shown in the drawings, one such procedure for manufacturing these teeth separately would be co~d isostatic pressing in polymeric molds shaped like the final tooth configu-ration desired. The mold would be identical for the three em-bodiments of cutting teeth, but the introduction of the various powder fractions would be different for each tooth. The process for tooth 32 would involve spraying the carbide-rich fraction A with a carrier fluid into the tooth mold initially, then grad-ually changing to fraction B and ending up with fraction C.
After evacuating the residual carrier vehicle,pressure would be applied to the mold to form the cutting tooth 32. The resulting green compact would then be densified by sintering or HIPing.
Figures 7 and 8 are partial cross-sectional views of tungsten carbide cutting elements commonly termed, "inserts".
In Figure 7 insert 110 is formed in the conventional insert shape but exhibiting the gradient composite concept of the present in-vention. For example, insert 110 comprises a generally trunca-ted conical protrusion 112 extçnding upward from a generally cylin-drical base portion 113. A central axial core section is made '5~
~57606 .
up of the carbide-rich material ~ extending throughout the length of insert 110. The mixed component s is located radially out-ward from A, and the basic matrix metal C is located around the surface of the insert. The carbide-rich fraction extends from the very tip of truncated portion 11 to the very base of portion 112.
Conversely, in Figure 8, insert 111 has a conical base portion 115 and a truncated conical protruding portion 114.
Protruding portions 114 and 112 could alternatively be formed in another geometrical shape, such as hemispherical, pyramidal, ogive, compound conical, or any combination of these. Also base portions 113 and llS could be formed of any geometrical shape which lends itself to easy fusion into the cutter sh~ell. The base portion 115 is made conical for easy welding by a beam wel-der such as an electron beam, which can be easily rotated to form the conical weld line along the surface of base 115. Other sur-face configurations could be used on base 115 for other types of weldin~. For example, for friction or inertia welding, any easily formed surface of revolution, such as spherical or para-~ bolic, could be employed.
Insert 111 has a carbide-rich material extending all the way across the top surface of the truncated portion 114 of the insert. The carbide-rich material A basically comprises the top end or the cutting end of the insert, and the composite gradient extends downward towards the lower end of the insert.
The process for manufacturing the inserts shown in Figures 7 and 8 is very similar to that described above with respect to Figures 4 through 6, i.e., filling the die cavity of a station-ery or rotating die, followed by compaction and/or encapsulation, and then sintering or HIPing.
- ~57606 This results in the gr~dient co~posite structures illus-trated in Figures 7 and 8 for the insert type cutting elements, which inserts e~hibit localized tungsten carbide-enriched areas gradually changing to an almost pure steel alloy, cobalt alloy, or other matri~ metal area such as indicated at C. The finished inserts are then inserted into openings in the conventional cut-ter bodies by interference fitting or fusion techniques.
In the above-described process, various alloys and elements may be utilized and substituted in the makeup of com-ponents A, B and C. For example, when manufacturing complete cutters such as illustrated in Figures 2 and 3, the components A, B and C are selected to provide a gradient ranging from tungs-ten carbide to a bearing steel. For example, compon~ent A would comprise a powdered tungsten carbide-cobalt mixture having about 14 to 14.5% cobalt and the remainder tungsten carbide, with a tungsten carbide grain size of 1.5 to 2 microns. Component B would be a powdered metal comprising about 18 to 19~ cobalt and the remainder powdered tungsten carbide, with the tungsten carbide grain size being about 1 to 1.5 microns. Component C
would be t prealloyed atomized powder of a be-aring steel such as AISI 52100.
The rate of powder feed with respect to time for this particular example is illustrated in the graph of Figure 10.
The initial powder feed would be substantially all of the A com-ponent, with the feed-rate decreasing at a non-linear rate.
Concurrently, the feed-rate of B would begin at zero and increase at a non-linear rate to a maximum level at approximately the same time the A powder feed-rate ceases. The B feed-rate would con-tinue for a short period of time and then be abruptly stopped while the feed-rate of C is abruptly initiated at substantially - ~57606 the same time that the s rate is stoppod, and at subst~ntially the same level.
As a result of this component feed-rate matrix, a large amount of the tungsten carbide-rich powder A will be placed in the outer regions of the mold cavity, and then the immediately-inward regions receive primarily the B material having an in-creased percentage of the cobalt matrix and a decreased percen- .
tage of tungsten carbide, with the interior portion of the mold`
cavity having substantially pure alloy steel. It should be noted that this feed diagram illustrated in Figure 10 appears to ini-tiate the discontinuity or gradient between materials B and C, but this is not detrimental because of several factors. The elastic and plastic behaviors of materials B and C a~e very simi-lar, as well as the temperature coefficients of expansion for these two materials. Likewise, a certain amount of migration and diffusion between the two materials will occur during the densification process.
In addition to this example of forming the cutters of Figure 2, a second exampIe could be utilized to obtain dif-ferent material properties with the gradient composites. For instance, the A material would comprise a powder having lO~ co-. _ balt and 90~ tungsten carbide, with a tungsten carbide grain size of 2 to 3 microns. The B component would comprise approximately 18 to l9~ cobalt powder, with the remainder being tungsten car-bide having a grain size of l to 1.5 microns. Component C would comprise a powdered mixture with 60~ of the powder comprising an iron/nickel/carbon alloy, with the remainder being tungsten carbide of sub-mic~on particle size.
~;7606 .
Figure 11 illustrates a feed rate graph ~or use with this set of powder components. As in the other examples, powder component A is first introduced into the cavity in large quan-titiesl and the introduction of powder A decreases in a non-linear fashion with time. Component B begins introduction and increases non-linearly as A decreases. The feed rate of component B peaks and begins decreasing, with component C being introduced at a point approximately coincidinq with the peak of component B and increasing at a non-linear rate to a point where component C
is abruptly terminated. Component A and component B are both terminated during the increase in feed rate of component C.
Although the aforementioned example is stated as being particu-larly useful in manufacturing the cutters of Figures 2 and 3, it should be noted that this system of component com~ositions and feed rates would similarly be advantageous for manufacturing the inserted cutting teeth, as shown in Figures 4 through 8.
Another example of compositions which would be particu-larly useful for manufacturing the cutter of Figure 3 and/or the inserted cutting elements of Figures 4 through 8 would consist of component A having about 14.5 to 15% iron/nickel/carbon alloy and the remainder a tungsten carbide having a grain size of 1.5 to 2 microns. Component B would be a powder having about 25% of the iron/nickel/carbon alloy, with the remainder a tungsten car-bide having a grain size below 1 micron. Component C would com-prise about 60% of the iron/nickel/carbon alloy, with the remain-der being sub-micron sized tungsten carbide powder. The time-feed-rate relationship of this example would be similar to that of the immediately preceding example, as illustrated in Figure 11. As previously mentioned, this set of components and the asso-ciated time-feed-rate relationship would be useful in manufac-turing both integral cutters and replaceable cutting teeth.
~ ~57606 A fourth example o~ the component feed-rate relation-ship, which is particularly useful in manufacturing the inserts illustrated in Figures 7 and 8, would be one utilizing about 10 to 10~5go cobalt and about 90~ tungsten carbide, with a grain size S of 2 to 3 microns for component A. Component B would comprise about 14 to 14.5% cobalt and the remainder tungsten carbide with a grain size of about 1.5 to 2 microns. Component C would com-prise about 18 to 19~ cobalt and the remainder a tungsten car-bide having a grain size of about 1 to 1.5 microns. The mate-rials of this example would be utilized in a feed-rate-time re-lationship similar to that disclosed in Figure 9. An insert ma-nufactured according to this example would be placed in a cutter shell very similarly to the placement of conventional inserts.
The cutter shell would be drilled with holes, and th~ inserts would be press-fit into the drilled holes.
The inserts, or cutting teeth, formed by the third ex-ample above, preferably would be welded into the cutter shell, or might be fusion-bonded in the cutter. The inserts or cutters formed according to the second example differ from the components manufactured by the last two examples in that in addition to the gradient in hard metal fractions, an additional gradient is intro-duced -- that being the chemical gradient between the tungsten ~arbide material and the iron/nickèl/carbon alloy. Likewise, the first example introduces the additional chemical gradient between the tungsten carbide hard metal fraction and the iron/
nickel/carbon alloy.
Although the examples and descriptions given above re-lating to the processes and products formed by the present inven-tion deal entirely with the use of three component systems, i.e., A, B and C, it can be seen that a simpler system utilizing only ~L~57606 two components, i.e., A and 3, could be utilized, although the results obtained might not be as desirable as the three-component system. The two-component system might comprise a first component A, which is a powdered binder metal or binder metal alloy, and a second component B, which is a pure powdered tungsten carbide.
This two-component system would be particularly advantageous in manufacturing the insertable cutting elements such as those dis-closed in Figures 7 and 8. Conversely, a system could be uti-lized to implement the present invention wherein more than three components are added together to form a more complex gradient within the cutting structure. For example, a four-component sys-tem can be visualized in which the A component may comprise a pure binder metal or binder alloy powder; the B component may comprise a pure powdered tungsten carbide; the C com~onent may comprise a mixture of a binder metal and the tungsten carbide, or the tungsten carbide and a bearing steel alloy; and the D
component may comprise a pure bearing steel alloy. Even further visualizations can foresee five- and six-component systems for manufacturing the cutting structures, or even more.
Thus, it can be seen from the description given above that this invention reveals methods for manufacturing unique, gradient composite cutting structures particularly advantageous for use in underground drilling tools. These unique methods and the novel articles manufactured thereby provide cutting struc-tures which have greatly reduced, and in some cases eliminated, the previously mentioned undesirable metallic and geometric notches which lead to early failure in conventional drilling equipment.
Primarily these notches are eliminated by the provision of a gradually changing composite material which goes from an almost pure cemented tungsten carbide fraction to an almost pure alloy steel or matrix metal fraction, with the tungsten carbide frac-~157606 tion being located in the areas of hi~h ~oint contact loading and high erosion, and the matri~ metal or alloy steel being in areas requiring toughness and strength as well as areas requi-ring machineability and hardenability suitable for bearing and seal surfaces. Between the points of high tungsten carbide con-tent and high alloy steel content, the change from one fraction to the other is gradual rather than abrupt, and as a result, regions of high stress normally occurring at metallic and geo-metric notches have been reduced or eliminated. In addition to this location of gradual gradients and elimination of notches and discontinuities, the properties of the cutting structures can also be varied desirably by changing the rate of gradient utilized in the entire cutting structure and/or changing the rate of gradients in particular regions of unusual high s~ress and/or erosion occurrences. Furthermore, the gradients can be utilized to provide residual compressive stresses in favorable locations in a finished component to increase the effective fracture re-sistance of that element. Other parameters can be closely con-trolled and varied by utilizing the present invention, i.e., the grain size of the tungsten carbide material can be varied to ob-tain advantages in the different sized grain structures, the amounts of matrix material in the tungsten carbide fraction can be varied to obtain varying hardnesses in the resulting cutting elements, and the alloy content of the C fraction can likewise be varied to obtain particular hardenability in the bearing surface areas.
Thus, the present invention embodies the use of inten-tional variation in the fraction, composition, shape, size and/or distribution of phases in a cemented carbide/alloy steel composite to produce an insert or onsert with continuously varying proper-ties. The property gradients can be designed to accomodate stress ~ 57606 field variations resulting from geometr~ and loading charac-teristics.
Al~hough certain preferred embodiments of the present invention have been herein described in order to provide an understanding of the general principles of the invention, it will be appreciated that various changes and innovations can be effec-ted in the desired composite gradient structure without depar-ture from these principles. For example, various residual stresses may be introduced strategically within the cutting element to increase resistance to failure from cracking and/or erosion.
Similarly, the present invention can be utilized to reduce dis-continuities and notches in composite elements manufactured from metallic fractions other than cemented carbides and ulloy steels.
In any event, whatever fractions present in the cutting struc-ture, the present invention allows one to vary the composite gra-dient so that the hard phase may possess orientational variation with respect to location, a changing volume fraction, and aspect ratio, and the element may also possess a varying metallurgical chemistry. The binder phase metallurgy could be structured to evidence compatible variation. Additional phases can be utilized in the composite to result in a greater number of potential vari-ations which, in light of this invention, would be known to those skilled in the art of metallurgy. It is also clear that, whereas this invention is illustrated and described in relation to drill-ing and cutting tools, that it should not be limited thereto, and can be applied by those skilled in the art to any structural metal component, given the inventive steps disclosed herein.
All modifications and changes of this type are deemed to be em-braced by the spirit and scope of the invention except as the same may be necessarily limited by the appended claims or reason-able equivalents thereof.
GRADIENT COMPOSITE METALLIC
STRUCTURES AND GRADIENT
COMPOSITE METALLIC PRODUCTS
~ACKGROUND OF THE INVENTION
The present invention generally relates to drilling bits utilized in the oil well drilling industry and in the min-ing arts, and more particularly involves a uni~ue metallic com-position for the cutting elements utilized in drilling bits.
In the conventional drill bit technology, there are generally two kinds of rolling cutter drill bits, as well as what is termed drag bits having no rolling elements. The rolling cutter drill bits are generally of the type having cantilevered frusto-conical cutters such as the tri-cone bit, and there are additionally bits having cutters mounted transversly on axles supported at each end by saddles, which in turn are affixed to large cutting heads. This second type of rolling cutter bit primarily is used in the mining and tunneling industries. In the tri-cone rolling cutter type of bit, there are generally two kinds of cutter struc-tures utilized, the "milled tooth" cutter, and the insert cutter.
In the milled tooth cutter, a large forqing is milled away, leav-ing protruding, sharp, wide chisel-shaped teeth as the cutting elements. These projecting teeth may have a hard material, such as tungsten carbide, welded to their faces to increase their ero-sion resistance. The cutter bodies themselves may be carburized and hardened to increase their resistance to breakage and wear.
In addition to the milled tooth cutters, rolling cutter drill bits commonly utilize insert type cutters wherein a smaller original cutter body is utilized with a minimum amount of machin-ing, and holes are drilled circumferentially around ~he cutter body to receive hard metal cutting inserts which are pressed there--` llS7~06 into. These hard metal inserts generally are formed of a tungs-ten carbide composite made in a generally cylindrical shape with a pointed protruding portion. The insert type cutter bodies generally are carburized and hardened prior to insertion of the inserts.
In the mining industry, the saddle type cutters most often used are the milled tooth variety, although the insert type cutters are becoming more widely used. The formation of these cutters is similar to that as described above with respect to the tri-cone drilling bit cutters. In the formation of the rol-ling cone cutting structures utilized both in the tri-cone bits and the mining bits, the two types of cutters can generally be classified as utilizing both gradient techniques and composite techniques, although none of the conventional cutters have com-bined these two techniques to arrive at a gradient composite me-tallic structure.
The term "composite" is used in the microstructural sense herein, as is commonly known in the fields of metallurgy and materials science. It refers to materials having micro- ~;
structures composed of at least two individual phases, the ;
volume fraction of a minor phase being at least 10~, which are bonded together in such a manner that the average properties of the composite are determined by the individual properties and morphology of each phase. This usage is distinct from that where an engineering structure may be referred to as a "composite" when it is comprised of two or more distinct, relatively large regions, bonded, coated, welded, or otherwise joined or internally transformed, forming a heterogeneous unit.
See--THE PRINCIPLES OF ENGINEERING MATERIALS, Barrett, Nix and Tetelman, Prentice-Hall, Inc., 1973, pp. 316 - 317--.
' ~L~57606 For e~a~ple, both the milled tooth cutter and the insert type cutter utilize the composite structures in that they both have a steel alloy cutter body to which is added a hard metal cutting surface, or cutting element. In the milled tooth S cutter the composite hard metal element is added as a tungsten carbide alloy weldment which is fused to the cutting surfaces on the teeth, the gage, and portions of the cutter body. In the insert type cutter, the composite element is added by the inser-tion of the cemented carbide insert into the alloy steel cutter shell. The result of these two types of composite metallurgical construction is a "metallurgical notch", where a very sharp gra-dient is formed across the interface between the hard metal and the alloy steel. In addition to this metallurgical notch, or discontinuity, the composite formed thereby also suf~ers from a disadvantage in that a geometrical notch is also usually formed at the juncture. These metallurgical and geometrical notches serve to weaken the resulting composite metal component and con-tribute to earlier failure of the cutting structure. These discontinuities in elastic moduli, coefficients of thermal ex-pansion, and yield characteristics limit drilling performance by affecting the residual stress distributions and applied stress distributions in service. These characteristics and changes re-~
sult from all of the different techniques which have been uti-lized in conventional cutter construction for xeducing deforma-tion and improving wear-resistant qualities on drilling equip-ment.
The composites utilized in conventional cutters have increased the mechanical strength, toughness and hardness but have not efficiently optimized these characteristics for drill-ing equipment. In addition to the welding of hard metal, such ~ as cemented carbides, on the cutting structures, other conven-;' .
~57606 tional techniques have involved brazing of the cemented carbides, plasma spraying of cemented carbide coatings, and chemical and electrical deposition of coatings having high carbide fractions.
All of these techniques suffer from the above-mentioned mechani-cal and metallurgical discontinuities at the joint interface.
Likewise, the insert cutter construction has been utilized to improve the mechanical strength, toughness and wear resistance of the cutting structure, but it still suffers from the elastic strain requirements of the interference fits, in addition to the limitations of the steel-composite interface on load bearing abi-lity.
The use of mechanical property gradients in convention-al drilling tools has been known and accepted for many years.
For example, gradients are introduced into the cutting structures by the case hardening, carburizing treatment of steels. The re-sultant gradient of a carburized case-hardened steel comprises a hard brittle outer surface shell with a tapering-off of the hardness and increase in toughness towards the interior of the part. This has been successful in reducing gaLling and spalling of bearing surfaces and other high unit loading contact areas, ~; but offers little improvement to erosion resistance which is preva-lent in rock drilling. Also, this type of gradient is generally relatively shallow, usually extending no more than 0~050 inches into the steel component, thus subjecting the surface to crack-ing or failure by plastic deformation. Other types of mechani-cal property gradient-producing processes include laser and in-duction hardening, nitriding and boronizing.
The present invention overcomes these disadvantages and provides an optimum cutting structure by the use of gradual or continuous gradients across the geometry of the cutting .
- ~57606 structure. This continuous or gradual gradient substantiall~
eliminates the interface and the resultant geometrical and meta-llurgical notches found in the conventional cutter construction.
The elimination of the discontinuities may involve varying seve-S ral different parameters to achieve different desirable techniques.
For instance, the composition, the fraction, the shape, the size and the distribution of phases in a cemented carbide composite may be systematically varied by powder metallurgy techniques to produce an insert with continuously varying properties. The gradient through the insert can be arranged so that a hard, stiff, abrasion-resistant cemented carbide structure exists at the tip of the insert, merging into a tougher, softer cemented carbide structure in the regions of high bending stress lower in the in-sert body. The gradient across the inserts can also ~e arranged such that when fused to the normal alloy steel cutter shell, the attachment surface of the insert can be substantially of the same composition as that of the alloy steel cutter shell so that the added insert becomes an integral part of the cutting struc-ture as though originally formed therewith, and a hard metal core extends downwardly along the central longitudinal axis of the insert.
In a second embodiment of the invention, the cutting structure is formed in a single operation rather than by the addition of inserts to a cutter shell. In this embodiment, the cutter and the teeth structure are formed in a single manufac-turing operation utilizing powder metallurgy techniques. A pro-grammable mixing system for mixing the alloying components of '~ a powdered metal alloy serves to place the proper concentrates of the cemented carbides in the locations requiring the proper-ties of cemented carbides and gradually reducing the cemented carbide fraction as you move geometrically away from these criti-cal points. The resulting cutting structure therefore has con-centrated fractions of cemented carbide in the high-stress, high-erosion areas with a gradual decrease in the hard metal component away from these critical areas towards the body of the cutter. The alloyed ~owder metallurgy components are then densi-fied into a single integral cutting structure utilizing conven-tional powder metallurgy techniques, such as hot isostatic press-ing. Then the completed cutter is removed from the pressing die and minor machining operations can be performed to create smooth bearing surfaces and seal surfaces within the cutter where required. Thus, it can be seen that the resulting drilling bit cutter offers an optimum metallurgical cutting structure in that it utilizes the desirable effects of the composites, such as ce- .
mented carbides, in the locations on the cutter wher~ such char-acteristics are desirable, and the desirable characteristics of a tough resilient core, such as the alloy steels, for strength and foundation in the cutter shel- itself with a smooth continu-ous gradient between the cemented carbide and the alloy steel to greatly reduce or eliminate discontinuities and their resul-tant stress risers. In addition, the locations of the gradientsand the gradient rates can be manipulated to provide favorable compressive residual stress patterns in a finished component, thereby raising the effective fracture resistance o~ the result-ing cutting structure.
Thus broadly, the invention contemplates.a ~owder met-allurgical method of constructing a cutter for a rolling cutter drill bit which comprises providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy, providing a second powder comprising a powdered binder metal or alloy or a mix-ture comprising a powdered refractory material and a powdered binde.r metal or alloy, present in a lesser proportion ~,~ by volume than in the first powder, forming the ~ 57606 cutter of the first and the second powders, mixing the powders while forming the cutter and introducing into a first region of the cutter a mixture having a first pre-selected proportion of the first powder relative to the second powder, and changing the relative proportions of the powders while mixing to introduce into a second region of the cutter a mixture having a second preselected proportion of the first powder relative to the second powder and a continuous gradient in the relative proportions of the powders between the regions. The powders are then densified into a solid cutter having a gradient in composition and properties from the first region to the second region.
The invention also includes the cutter product of the inventive method for rock cutting tools and the cutter includes a body which comprises an exterior cutter surface region having cutting means thereon, an interior cavity having bearing surface means there}n, and the cutter body having a portion of substantial thickness comprising a densified powder metallurgical composite of at least two varying phases, which has a substantially continuous mechanical property gradient through the body portion.
In another embodiment the invention includes a cut-ting element for attachment to a rolling cutter which is rotatably mounted on a drill bit and that cuttlng element comprises a root portion adapted for engagement in a bit cutter, a cutting portion on the root portion adapted to protrude from a bit cutter in a cutting orientation, and wherein the cutting element comprises a portion o~ substantial thickness comprising a densified powder metallurgical composite of at least two vary- -ing phases, with the composite having a substantially continuous mechanical property gradient through the cutting portion.
-6a-': :
~L157606 In a further embodiment the invention contemplates an insert for use in an insert-type rolling cutter drill bit which comprises a geometric base portion for insertion into a matching hole in a drill bit cutter, a tapered, geometrical cutter portion formed on the base portion and adapted to protrude from ~ ~ole in a drill bit cutter with the insert cutter por*ion comprising a densified powder metallurgical composite of at least two varying phases, and with the com-posite having one portion in which one phase is present in a large volume fraction relative to the other phase, another por-tion in which the other phase is present in larger volume fraction relative to the one phase and having a substantially continuous mechanical property gradient therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
:
Figure 1 is a schematic drawing illustrating one e~cdi-ment of the powder mixing process. Figure 2 is a cross-sectional schematic drawing illustrating the apparatus for manufacturing _a powdered metal cutter. Figure 3 is a partial cross-sectional drawing illustrating a rolling cutter manufactured by the pro-~.
-6b-~57606 cess of Figures 1 and 2. ~igures 4, 5 and 6 illustrat~ cross-sectional partial views of dlfferent embodiments of the present invention utilized in intcgral tooth cutters. Figures 7 and 8 illustrate partial cross-sectional views of inserts l,lade accord-ing to the present invention. Figures 9-11 illustrate graphi-cally the relationship between powder feed rates and time.
Figure 9 appears with Figure 1.
DESCRIPTION OF THE PREFERRED E~BODI~lE~TS
Referring now to Figure 1, which illustrates a sche-LO matic diagram indicating one particular method of forming the gradient composite metal structures of the present invention, a plurality of powder supply bins feed powder through a closely controlled auger system into a mixing chamber fro~ ~w~ence it flows into a rotating die. In this embodiment, a primary supply bin L5 10 is supplied with a powdered metal A having a high percent car-bide fraction. A secondary supply bin 11 is provided with a powdered metal 8 having a low percent carbide fraction, and a tertiary supply bin 12 is supplied with a powdered metal C com-prising a steel alloy havinc superior bearing qualities. Pri- ``
'0 mary bin 10 is provided with a funnel-shaped wall 13 feeding through a section 14 into a screw auger tube 15. A rotating screw 16 is rotatably located in channel 15 to accurately dis-pense powder A into the mixing chamber 17. The feed auger 16 is preferably microprocessor-controlled to precisely discharge controlled amounts of powder A at variable rates into chamber 17. LiXewise, secondary bin 11 has a funnel-shaped wall section 18 feeding into a narrowed throat section 19 and thence into auger tube 20 having screw auger 21 rotatably mounted therein and tightly controlled by a second microprocessor circuit (not shown). Tertiary bin 12 has a funnel-shaFed wall section 22, throat section 23, screw auger tube 24, and feed auger 25, which ~ 57606 is also mic-o?rocessor-co~t-olled or ~recisc moterin~ of ~ow-dercd metal C into mi.~ing chamber 17. Po~der dispensed in mi~-ing chamber 17 flo~s through a vibratable discharse chute 26 into a rotating die 27 whenceforth it is moved by centrifu~al force out~ard into the outer cavities of die 27. ~ vibrator 48 is lo-cated on chute 26 to facilitate thc flow of powder therethrough.
Figure 9 illustrates a schematic graph showing the feed rates of the various powders A, B and C into die 27 in a typical pro-cess embodying the present invention. The vertical axis of the Figure 9 graph represents the rate of powder flow into the mix-i~g c~am~er 17and the horizontal axis indicates the time continuum.
It can be seen from Figure 9 that by means of the microprocessor system ~not shown), which system is well known in the art, the volume of powder flow initially is heavy in componen~ A and light in component B, with no co~ponent C being introduced. The vol-ume feed rate of component A decreases with time at about the ; same rate component B increases with time until a point where component B peaks out slightly before component A is completely shut off, Component B then begins to decrease in volume feed ~ 20 rate, and at the time component A is terminated, component C
i begins feeding into chamber 17. Component B decreases to a point where only component C is being introduced into the rotating die ; and component C is introduced therein until the die cavity is completely filled.
By the use of the present system, the high percent car-bide fraction A ends up in the outer extremities and surface por-tions of the product being formed in the rotating die 27. Then moving inward towards the inner portion of the comoonent being built, the percent of high carbide fraction cornponent A gradu-ally reduces as the percent of co~ponent B increases, resulting in a gradual continuum of hish carbide fraction to low carbide ~.157606 fraction. Then towards the inner portion and center of the co~-ponent is the final component C comprising a powdered metal of an alloy steel having superiar bearing surface qualities.
It should be noted that, in powder metallurgy processes, the powdered metal constituents of the part being manufactured must be compressed to remove the gas voids and heated to solidify and strengthen the part. Thls is normally done in one of several ways. One method uses a pre-compaction of the powder into a "green" part and then sintering at a temperature above the liquidus temperature to fuse the powder. The sintering usually occurs in a vacuum or inert gas atmosphere. An alternative process comprises Hot Isostatic Pressing, commonly termed, "HIPing".
Other processes such as hot forging are also used. ~or conven-ience, all such processes will be occasionally referred to here-in as "densification".
Referring now to Figure 2, the rotating die 27 is illustrated in close-up cross-sectional view. The inner configu-ration of die 27 is adapted for manufacturing a typical integral tooth rolling cutter for a tri-cone drilling bit. In this par-ticular embodiment r die 27 comprises a tough metal outer shell 28 made of a material such as steel and a disoosable material 29, such as castable ceramic, molded by a conventional process such as a lost-wax or investment casting process. Ceramic materi-al 29 is formed in the shell 28 with an internal cavity 30 shaped to correspond to the external dimensions of an integral tooth cutter body for use in the aforementioned drilling bit. This cavity generally has a body section 31 which has radially out-wardly projecting tooth sections 32. Above the cutter cavity is a generally cylindrical filler neck 33 with a funnel-shaped top 34. During the powder-filling stage of forming the cutter, ~: .
;7606 powdcr ~ is first fed in~o the rotatincJ die 7 SuC~l that it ~or~s around thc surface of thc teeth and cutter body as indic~tcd at 35. The distribution of po~dcred metal along the irregular surfAce of the die cavitr may be controllcd by the rotary die speed, oricntaticn of the die rotational axis with respect to the vertical, and/or the geometric configura~ion of discharge chute 26. This configuration may be selected to provide a stream of any desirable width or may be adapted to produce a uniform or non-uniform "curtain" of powder. Powder A is heavy in the cemented carbide component of the final cutter metallurgical content. Because of the rich feed rate of component ~ during the initial filling of cavity 30, the outer extremities of cavi-ty 30, such as indicated at 35, have an extremely high percen-tage content of the cemented carbide component movin~ inwardly from the outer surface of the cavity. A gradually decreasing amount of cemented carbide and increasing amount of matrix ma-terial is encountered in the area 36. This corresponds to the decreasing feed rate of component A and the increasing feed rate of component B, as shown in Figure 7. Near the center of cavity 30 is relatively pure component C corresponding to the far right-hand portion of the graph in Fig~.re ~. This is indicated at 37 in Figure 2. A phantom line 38 is disclosed showing the desired final outline of the internal portion of the cutter after it has been densified into the final product, and machined to create internal bearing areas.
After the varying gradients of the powdered metals have been added to cavity 3C, the die shell is closed by steel cap 40 which is welded across the top, and the gas content is evacu-ated through pipe 50. The die is then placed in a HIPing cha~-ber where a pressurized inert gas such as argon is introduced.
The hydrostatic pressure of the inert gas is increased and the ~ ~.57606 temperature in the chamber is simultaneously increased untll cap 40 is deformed inwardly. The powdered metal is thus comp-ressed radially outward into cavity 30 to form the final sintered metal par~ having the external shape shown in Figure 3. A ter a sufficient period of time, pressure, and temperature to com-pletely solidify the powdered metal in cavity 30, cap 40 is re-moved and the ceramic material 29 is fractured to remove the c~m-pleted, solidified cutter.
Referring to Figure 3, the cutter 41 is shown after removal from the centrifugal die. Cutter 41 may then be machined to provide bearing surfaces 42 and 43 and a seal cavity 44.
Cutter 41 in its final state is a single integral body member having protruding teeth 45, with the body 41 and teeth 45 exhibi-ting a gradual metallurgical gradient beginning with a high tungsten carbide surface and thickness 46, and ending in a low carbide, high steel bearing area 47 for superior bearing surfaces 42 and 43. The gradient from the extremely high carbide content area 46 to the-extremely low carbide content 47 is almost uniform and gradual across this thickness. This resulting cutter has no metal-lurgical notches, as mentioned wlth respect to the prior art, and as a result, offers extreme hardness and erosion resistance at the outer surfaces and along the cutting members 45 while the inner area 47 provides extreme toughness and hardenable surface material for bearings and seals. Also, the cutter exhibits a surface greatly freed of pores and defects.
Referring now to Figures 4 through 6, various construc-tions for cutter teeth are disclosed in broken-out, partial cross-sectional illustrations. Figure 4 illustrates the teeth 32 as shown in Figures 2 and 3. In tooth 32, the entire outer ~ ~ 57606 surface comprises the tungsten carbide-ric~ component ~ with a gradual decrease in carbide in area B and a relatively pure alloy steel in area C. Although tooth 32 is disclosed as part of the integral cutter member 41, an alternate method of manu-facturing cutter 41 is to form the teeth in a separate operation.
Each tooth could be precompacted in green form utilizing powder metallurgy techniques, and then inserted into their proper cavi-ties in die 27. Then the remainder of powder to form the cutter body is added to the die and the entire cutter is then densified by Hot Isostatic Pressing. Alternatively, the teeth and cutter can be densified separately and then fused together by means such as electron beam welding.
Figure 5 illustrates a different gradient ~oncept em-bodied in a tooth member 132. In this embodiment, a carbide-rich fraction A is disclosed running longitudinally through the center of a tooth member 132 and do~nward into the root section 133.
The rich carbide section comprises a generally planar shape run-ning transversely through tooth member 132. A gradient is es-tablis~ed with material B on both sides of the carbide-rich plane A. The remainder of root section 133 is made up of primarlly steel C. The high-modulus core of this structure is particular-ly adapted to carry drilling stress into the cutter bodv by an internal route rather than across defect-prone surfaces.
Figure 6 illustrates in a broken-out, partial cross-sectional isometric view a third embodiment 232 of cutting teeth for cutter body 41. In tooth 232, a carbide-rich area is formed along the sur~ace of the tooth and the root section, and also a carbide-rich area is formed down through the center of the tooth in a planar shape similar to that of ~igure 5. Actually, the cutting tooth 232 is a combination of the structures 32 and 132.
~1~7606 ~he remainder of the tooth and a portion of the root section 233 comprise the mi~ed component B, and the rcmainder of root por-tion 233 is made up of pure steel alloy C. As previously men-tioned, manufacturing techniques to form the cutting teeth 32, 132 and 232 can be utilized in the process of Figure 1 to form an integral cutter assembly or alternatively, the individual cutting teeth may be formed separately in a gradient forming process and then densified as a unit with the body or may be separately densified and then added to the cutter body prefer-ably along isopleths of composition by means such as welding or fusion.
A~though not shown in the drawings, one such procedure for manufacturing these teeth separately would be co~d isostatic pressing in polymeric molds shaped like the final tooth configu-ration desired. The mold would be identical for the three em-bodiments of cutting teeth, but the introduction of the various powder fractions would be different for each tooth. The process for tooth 32 would involve spraying the carbide-rich fraction A with a carrier fluid into the tooth mold initially, then grad-ually changing to fraction B and ending up with fraction C.
After evacuating the residual carrier vehicle,pressure would be applied to the mold to form the cutting tooth 32. The resulting green compact would then be densified by sintering or HIPing.
Figures 7 and 8 are partial cross-sectional views of tungsten carbide cutting elements commonly termed, "inserts".
In Figure 7 insert 110 is formed in the conventional insert shape but exhibiting the gradient composite concept of the present in-vention. For example, insert 110 comprises a generally trunca-ted conical protrusion 112 extçnding upward from a generally cylin-drical base portion 113. A central axial core section is made '5~
~57606 .
up of the carbide-rich material ~ extending throughout the length of insert 110. The mixed component s is located radially out-ward from A, and the basic matrix metal C is located around the surface of the insert. The carbide-rich fraction extends from the very tip of truncated portion 11 to the very base of portion 112.
Conversely, in Figure 8, insert 111 has a conical base portion 115 and a truncated conical protruding portion 114.
Protruding portions 114 and 112 could alternatively be formed in another geometrical shape, such as hemispherical, pyramidal, ogive, compound conical, or any combination of these. Also base portions 113 and llS could be formed of any geometrical shape which lends itself to easy fusion into the cutter sh~ell. The base portion 115 is made conical for easy welding by a beam wel-der such as an electron beam, which can be easily rotated to form the conical weld line along the surface of base 115. Other sur-face configurations could be used on base 115 for other types of weldin~. For example, for friction or inertia welding, any easily formed surface of revolution, such as spherical or para-~ bolic, could be employed.
Insert 111 has a carbide-rich material extending all the way across the top surface of the truncated portion 114 of the insert. The carbide-rich material A basically comprises the top end or the cutting end of the insert, and the composite gradient extends downward towards the lower end of the insert.
The process for manufacturing the inserts shown in Figures 7 and 8 is very similar to that described above with respect to Figures 4 through 6, i.e., filling the die cavity of a station-ery or rotating die, followed by compaction and/or encapsulation, and then sintering or HIPing.
- ~57606 This results in the gr~dient co~posite structures illus-trated in Figures 7 and 8 for the insert type cutting elements, which inserts e~hibit localized tungsten carbide-enriched areas gradually changing to an almost pure steel alloy, cobalt alloy, or other matri~ metal area such as indicated at C. The finished inserts are then inserted into openings in the conventional cut-ter bodies by interference fitting or fusion techniques.
In the above-described process, various alloys and elements may be utilized and substituted in the makeup of com-ponents A, B and C. For example, when manufacturing complete cutters such as illustrated in Figures 2 and 3, the components A, B and C are selected to provide a gradient ranging from tungs-ten carbide to a bearing steel. For example, compon~ent A would comprise a powdered tungsten carbide-cobalt mixture having about 14 to 14.5% cobalt and the remainder tungsten carbide, with a tungsten carbide grain size of 1.5 to 2 microns. Component B would be a powdered metal comprising about 18 to 19~ cobalt and the remainder powdered tungsten carbide, with the tungsten carbide grain size being about 1 to 1.5 microns. Component C
would be t prealloyed atomized powder of a be-aring steel such as AISI 52100.
The rate of powder feed with respect to time for this particular example is illustrated in the graph of Figure 10.
The initial powder feed would be substantially all of the A com-ponent, with the feed-rate decreasing at a non-linear rate.
Concurrently, the feed-rate of B would begin at zero and increase at a non-linear rate to a maximum level at approximately the same time the A powder feed-rate ceases. The B feed-rate would con-tinue for a short period of time and then be abruptly stopped while the feed-rate of C is abruptly initiated at substantially - ~57606 the same time that the s rate is stoppod, and at subst~ntially the same level.
As a result of this component feed-rate matrix, a large amount of the tungsten carbide-rich powder A will be placed in the outer regions of the mold cavity, and then the immediately-inward regions receive primarily the B material having an in-creased percentage of the cobalt matrix and a decreased percen- .
tage of tungsten carbide, with the interior portion of the mold`
cavity having substantially pure alloy steel. It should be noted that this feed diagram illustrated in Figure 10 appears to ini-tiate the discontinuity or gradient between materials B and C, but this is not detrimental because of several factors. The elastic and plastic behaviors of materials B and C a~e very simi-lar, as well as the temperature coefficients of expansion for these two materials. Likewise, a certain amount of migration and diffusion between the two materials will occur during the densification process.
In addition to this example of forming the cutters of Figure 2, a second exampIe could be utilized to obtain dif-ferent material properties with the gradient composites. For instance, the A material would comprise a powder having lO~ co-. _ balt and 90~ tungsten carbide, with a tungsten carbide grain size of 2 to 3 microns. The B component would comprise approximately 18 to l9~ cobalt powder, with the remainder being tungsten car-bide having a grain size of l to 1.5 microns. Component C would comprise a powdered mixture with 60~ of the powder comprising an iron/nickel/carbon alloy, with the remainder being tungsten carbide of sub-mic~on particle size.
~;7606 .
Figure 11 illustrates a feed rate graph ~or use with this set of powder components. As in the other examples, powder component A is first introduced into the cavity in large quan-titiesl and the introduction of powder A decreases in a non-linear fashion with time. Component B begins introduction and increases non-linearly as A decreases. The feed rate of component B peaks and begins decreasing, with component C being introduced at a point approximately coincidinq with the peak of component B and increasing at a non-linear rate to a point where component C
is abruptly terminated. Component A and component B are both terminated during the increase in feed rate of component C.
Although the aforementioned example is stated as being particu-larly useful in manufacturing the cutters of Figures 2 and 3, it should be noted that this system of component com~ositions and feed rates would similarly be advantageous for manufacturing the inserted cutting teeth, as shown in Figures 4 through 8.
Another example of compositions which would be particu-larly useful for manufacturing the cutter of Figure 3 and/or the inserted cutting elements of Figures 4 through 8 would consist of component A having about 14.5 to 15% iron/nickel/carbon alloy and the remainder a tungsten carbide having a grain size of 1.5 to 2 microns. Component B would be a powder having about 25% of the iron/nickel/carbon alloy, with the remainder a tungsten car-bide having a grain size below 1 micron. Component C would com-prise about 60% of the iron/nickel/carbon alloy, with the remain-der being sub-micron sized tungsten carbide powder. The time-feed-rate relationship of this example would be similar to that of the immediately preceding example, as illustrated in Figure 11. As previously mentioned, this set of components and the asso-ciated time-feed-rate relationship would be useful in manufac-turing both integral cutters and replaceable cutting teeth.
~ ~57606 A fourth example o~ the component feed-rate relation-ship, which is particularly useful in manufacturing the inserts illustrated in Figures 7 and 8, would be one utilizing about 10 to 10~5go cobalt and about 90~ tungsten carbide, with a grain size S of 2 to 3 microns for component A. Component B would comprise about 14 to 14.5% cobalt and the remainder tungsten carbide with a grain size of about 1.5 to 2 microns. Component C would com-prise about 18 to 19~ cobalt and the remainder a tungsten car-bide having a grain size of about 1 to 1.5 microns. The mate-rials of this example would be utilized in a feed-rate-time re-lationship similar to that disclosed in Figure 9. An insert ma-nufactured according to this example would be placed in a cutter shell very similarly to the placement of conventional inserts.
The cutter shell would be drilled with holes, and th~ inserts would be press-fit into the drilled holes.
The inserts, or cutting teeth, formed by the third ex-ample above, preferably would be welded into the cutter shell, or might be fusion-bonded in the cutter. The inserts or cutters formed according to the second example differ from the components manufactured by the last two examples in that in addition to the gradient in hard metal fractions, an additional gradient is intro-duced -- that being the chemical gradient between the tungsten ~arbide material and the iron/nickèl/carbon alloy. Likewise, the first example introduces the additional chemical gradient between the tungsten carbide hard metal fraction and the iron/
nickel/carbon alloy.
Although the examples and descriptions given above re-lating to the processes and products formed by the present inven-tion deal entirely with the use of three component systems, i.e., A, B and C, it can be seen that a simpler system utilizing only ~L~57606 two components, i.e., A and 3, could be utilized, although the results obtained might not be as desirable as the three-component system. The two-component system might comprise a first component A, which is a powdered binder metal or binder metal alloy, and a second component B, which is a pure powdered tungsten carbide.
This two-component system would be particularly advantageous in manufacturing the insertable cutting elements such as those dis-closed in Figures 7 and 8. Conversely, a system could be uti-lized to implement the present invention wherein more than three components are added together to form a more complex gradient within the cutting structure. For example, a four-component sys-tem can be visualized in which the A component may comprise a pure binder metal or binder alloy powder; the B component may comprise a pure powdered tungsten carbide; the C com~onent may comprise a mixture of a binder metal and the tungsten carbide, or the tungsten carbide and a bearing steel alloy; and the D
component may comprise a pure bearing steel alloy. Even further visualizations can foresee five- and six-component systems for manufacturing the cutting structures, or even more.
Thus, it can be seen from the description given above that this invention reveals methods for manufacturing unique, gradient composite cutting structures particularly advantageous for use in underground drilling tools. These unique methods and the novel articles manufactured thereby provide cutting struc-tures which have greatly reduced, and in some cases eliminated, the previously mentioned undesirable metallic and geometric notches which lead to early failure in conventional drilling equipment.
Primarily these notches are eliminated by the provision of a gradually changing composite material which goes from an almost pure cemented tungsten carbide fraction to an almost pure alloy steel or matrix metal fraction, with the tungsten carbide frac-~157606 tion being located in the areas of hi~h ~oint contact loading and high erosion, and the matri~ metal or alloy steel being in areas requiring toughness and strength as well as areas requi-ring machineability and hardenability suitable for bearing and seal surfaces. Between the points of high tungsten carbide con-tent and high alloy steel content, the change from one fraction to the other is gradual rather than abrupt, and as a result, regions of high stress normally occurring at metallic and geo-metric notches have been reduced or eliminated. In addition to this location of gradual gradients and elimination of notches and discontinuities, the properties of the cutting structures can also be varied desirably by changing the rate of gradient utilized in the entire cutting structure and/or changing the rate of gradients in particular regions of unusual high s~ress and/or erosion occurrences. Furthermore, the gradients can be utilized to provide residual compressive stresses in favorable locations in a finished component to increase the effective fracture re-sistance of that element. Other parameters can be closely con-trolled and varied by utilizing the present invention, i.e., the grain size of the tungsten carbide material can be varied to ob-tain advantages in the different sized grain structures, the amounts of matrix material in the tungsten carbide fraction can be varied to obtain varying hardnesses in the resulting cutting elements, and the alloy content of the C fraction can likewise be varied to obtain particular hardenability in the bearing surface areas.
Thus, the present invention embodies the use of inten-tional variation in the fraction, composition, shape, size and/or distribution of phases in a cemented carbide/alloy steel composite to produce an insert or onsert with continuously varying proper-ties. The property gradients can be designed to accomodate stress ~ 57606 field variations resulting from geometr~ and loading charac-teristics.
Al~hough certain preferred embodiments of the present invention have been herein described in order to provide an understanding of the general principles of the invention, it will be appreciated that various changes and innovations can be effec-ted in the desired composite gradient structure without depar-ture from these principles. For example, various residual stresses may be introduced strategically within the cutting element to increase resistance to failure from cracking and/or erosion.
Similarly, the present invention can be utilized to reduce dis-continuities and notches in composite elements manufactured from metallic fractions other than cemented carbides and ulloy steels.
In any event, whatever fractions present in the cutting struc-ture, the present invention allows one to vary the composite gra-dient so that the hard phase may possess orientational variation with respect to location, a changing volume fraction, and aspect ratio, and the element may also possess a varying metallurgical chemistry. The binder phase metallurgy could be structured to evidence compatible variation. Additional phases can be utilized in the composite to result in a greater number of potential vari-ations which, in light of this invention, would be known to those skilled in the art of metallurgy. It is also clear that, whereas this invention is illustrated and described in relation to drill-ing and cutting tools, that it should not be limited thereto, and can be applied by those skilled in the art to any structural metal component, given the inventive steps disclosed herein.
All modifications and changes of this type are deemed to be em-braced by the spirit and scope of the invention except as the same may be necessarily limited by the appended claims or reason-able equivalents thereof.
Claims (57)
1. A powder metallurgical method of constructing a cutter for a rolling cutter drill bit, said method comprising:
providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy, providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
forming said cutter of said first and said second powders;
mixing said powders While forming said cutter and introducing into a first region of said cutter a mixture having a first preselected proportion of said first powder relative to said second powder changing the relative proportions of said powders while mixing to introduce into a second region of said cutter a mixture having a second preselected proportion of said first powder relative to said second powder and a continuous gradient in the relative proportions of said powders between said regions; and densifying said powders into a solid cutter having a gradient in composition and properties from said first region to said second region.
providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy, providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
forming said cutter of said first and said second powders;
mixing said powders While forming said cutter and introducing into a first region of said cutter a mixture having a first preselected proportion of said first powder relative to said second powder changing the relative proportions of said powders while mixing to introduce into a second region of said cutter a mixture having a second preselected proportion of said first powder relative to said second powder and a continuous gradient in the relative proportions of said powders between said regions; and densifying said powders into a solid cutter having a gradient in composition and properties from said first region to said second region.
2. The cutter constructing method of claim 1 wherein said first-named mixture of powders is located along at least a portion of the cutting surface of said cutter and said second-named mixture of powders is located around at least a portion of the interior surface of said cutter.
3. The cutter constructing method of claim 1 wherein said mixture of powders formed into the shape of said cutter is densified by hot isostatic pressing.
4. The cutter constructing method of claims 1, 2 or 3 further comprising machining a bearing surface in said interior surface of the densified cutter.
5. A method of constructing an abrasion and fracture resistant cutter for rock and underground formation cutting, said method comprising:
securing a mold having a cavity substantially conforming to the desired exterior shape of said cutter;
forming a cutter in said mold by the steps defined in claim 1, and separating said densified cutter from said mold.
securing a mold having a cavity substantially conforming to the desired exterior shape of said cutter;
forming a cutter in said mold by the steps defined in claim 1, and separating said densified cutter from said mold.
6. The cutter construction method of claim 5 further comprising:
forming at least one powdered metal cutting element into a precompacted form having at least two different regions with mixtures of metallic phases with a gradient there-between; and placing at least one said cutting element into said mold cavity immediately prior to introducing said mix-tures of powders into said mold.
forming at least one powdered metal cutting element into a precompacted form having at least two different regions with mixtures of metallic phases with a gradient there-between; and placing at least one said cutting element into said mold cavity immediately prior to introducing said mix-tures of powders into said mold.
7. A method of forming a drilling bit insert having combined resistance to abrasion and bending stresses, said method comprising:
providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy;
providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
providing a cutter insert mold;
forming said insert of said first and said second powders;
mixing said powders while forming said insert and introducing into the central portion of said mold a mixture having a first preselected proportion of said first powder relative to said second powder;
changing the relative proportions of said powders while mixing to introduce into the outer portion of said mold a mixture having a second preselected proportion of said first powder relative to said second powder surrounding said central portion and extending to the outer surface of the insert formed thereon and a continuous gradient in the relative proportions of said powders between said central portion and said outer portion; and densifying said mixtures of powders into a solid insert having a gradient in composition and properties from said central portion to the outer surface thereof.
providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy;
providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
providing a cutter insert mold;
forming said insert of said first and said second powders;
mixing said powders while forming said insert and introducing into the central portion of said mold a mixture having a first preselected proportion of said first powder relative to said second powder;
changing the relative proportions of said powders while mixing to introduce into the outer portion of said mold a mixture having a second preselected proportion of said first powder relative to said second powder surrounding said central portion and extending to the outer surface of the insert formed thereon and a continuous gradient in the relative proportions of said powders between said central portion and said outer portion; and densifying said mixtures of powders into a solid insert having a gradient in composition and properties from said central portion to the outer surface thereof.
8. The method of claim 7 wherein:
said central portion comprises a large volume fraction of said refractory compound and a small volume fraction of said binder metal or alloy; and said outer portion comprises a smaller volume fraction of said refractory compound and a larger volume fraction of said binder metal or alloy.
said central portion comprises a large volume fraction of said refractory compound and a small volume fraction of said binder metal or alloy; and said outer portion comprises a smaller volume fraction of said refractory compound and a larger volume fraction of said binder metal or alloy.
9. The method of claim 7 wherein:
said central portion comprises a smaller volume fraction of said refractory compound and a larger volume fraction of said binder metal or alloy; and said outer portion comprises a large volume fraction of said refractory compound and a small volume fraction of said binder metal or alloy.
said central portion comprises a smaller volume fraction of said refractory compound and a larger volume fraction of said binder metal or alloy; and said outer portion comprises a large volume fraction of said refractory compound and a small volume fraction of said binder metal or alloy.
10. The method of claim 7, 8 or 9 wherein said re-fractory compound comprises a transition metal carbide, and said binder metal or alloy comprises a metal selected from the group of iron, nickel,cobalt, and copper.
11. The method of claim 7, 8 or 9 wherein said re-fractory compound comprises tungsten carbide, and said binder metal or alloy comprises a metal selected from the group of iron, nickel,cobalt, and copper.
12. A method of forming a drilling bit insert having combined resistance to abrasion and bending stresses, said method comprising:
providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy;
providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
providing a cutter insert mold;
forming said insert of said first and said second powders;
mixing said powders while forming said insert and introducing into the tip portion of said mold a mixture having a first preselected proportion of said first powder relative to said second powder;
changing the relative proportions of said powders while mixing to introduce into the base portion of said mold a mixture having a second preselected proportion of said first powder relative to said second powder and a continuous gradient in the relative proportions of said powders between said tip portion and said base portion; and densifying said mixtures of powders into a solid insert having a gradient in composition and properties from said tip portion to the base thereof.
providing a first powder consisting essentially of a mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy;
providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
providing a cutter insert mold;
forming said insert of said first and said second powders;
mixing said powders while forming said insert and introducing into the tip portion of said mold a mixture having a first preselected proportion of said first powder relative to said second powder;
changing the relative proportions of said powders while mixing to introduce into the base portion of said mold a mixture having a second preselected proportion of said first powder relative to said second powder and a continuous gradient in the relative proportions of said powders between said tip portion and said base portion; and densifying said mixtures of powders into a solid insert having a gradient in composition and properties from said tip portion to the base thereof.
13. The method of claim 12 wherein:
said tip portion comprises a large volume fraction of said refractory compound and a small volume fraction of said binder metal or alloy; and said base portion comprises a smaller volume fraction of said refractory compound and a larger volume fraction of said binder metal or alloy.
said tip portion comprises a large volume fraction of said refractory compound and a small volume fraction of said binder metal or alloy; and said base portion comprises a smaller volume fraction of said refractory compound and a larger volume fraction of said binder metal or alloy.
14. The method of claim 12 or 13 wherein said refractory compound comprises a transition metal carbide, and said binder metal or alloy comprises a metal selected from the group of iron, nickel,cobalt, and copper.
15. The method of claim 12 or 13 wherein said refractory compound comprises tungsten carbide, and said binder metal or alloy comprises a metal selected from the group of iron, nickel,cobalt, and copper.
16. A method according to claim 1, 7 or 12 in which said powders are admixed with a fluid carrier to form at least one slurry prior to introduction into said mold cavity and said slurry sprayed into said mold cavity.
17. A method according to claim 1, 7 or 12 in which the powders are mixed and the composition selectively changed during introduction into the mold cavity; and said mixing and changing of composition is con-trolled by a microprocessor.
18. A method according to claim 1, 7 or 12 in which said second powder comprises a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in said first powder;
additionally providing a third powder comprising a binder metal or alloy; and said powders being formed or introduced into a mold in compositions ranging from a mixture comprising said first powder in one region through intermediate mixtures comprising at least two of said powders in an intermediate region to a composition comprising said third powder in another region.
additionally providing a third powder comprising a binder metal or alloy; and said powders being formed or introduced into a mold in compositions ranging from a mixture comprising said first powder in one region through intermediate mixtures comprising at least two of said powders in an intermediate region to a composition comprising said third powder in another region.
19. A cutter for rock cutting tools including a cutter body comprising:
an exterior cutter surface region having cutting means thereon;
an interior cavity having bearing surface means therein; and said cutter body having a portion of substantial thickness comprising a densified powder metallurgical composite of at least two varying phases, said composite having a sub-stantially continuous mechanical property gradient through said body portion.
an exterior cutter surface region having cutting means thereon;
an interior cavity having bearing surface means therein; and said cutter body having a portion of substantial thickness comprising a densified powder metallurgical composite of at least two varying phases, said composite having a sub-stantially continuous mechanical property gradient through said body portion.
20. The cutter of claim 19 in which at least one of said phases is a refractory compound and at least one other phase is a binder metal or alloy.
21. The cutter of claim 20 in which said refractory compound is a transition metal carbide.
22. The cutter of claim 21 in which said metal carbide is tungsten carbide and said binder metal or alloy is iron, cobalt, nickel or copper.
23. The cutter of claim 19, 20 or 21 in which said composite gradient varies from one mixture of said phases having wear and deformation resistant properties at one point to another mixture of said phases having toughness properties at another point.
24. The cutter of claim 19, 20 or 21 in which said composite gradient varies from one mixture of said phases having wear and deformation resistant properties at one surface of at least part of said cutter body to another mix-ture of said phases having toughness properties in another portion of said cutter body.
25. The cutter of claim 19, 20 or 21 in which said composite gradient varies from one mixture or said phases having wear and deformation resistant properties at the exterior surface of said cutting means to another mix-ture of said phases having toughness properties in another part of said cutting means.
26. The cutter of claim 19, 20 or 21 in which said composite gradient varies from one mixture of said phases having wear and deformation resistant properties at an exterior surface including the exterior surface of said cutting means and the exterior surface of said cutter body to another mix-ture of said phases having toughness properties in another part of said cutter body around said cavity.
27. A cutting member having high surface resistance to galling and spalling and a tough strong core, said member comprising a body having substantial thickness; said body further comprising a densified powder metallurgical composite of at least two varying phases, said composite having a sub-stantially continuous mechanical property gradient there-through varying from one mixture of said phases having wear and deformation resistant properties at the exterior surface of said body to another mixture of said phases having tough-ness properties in the core of said body.
28. The cutting member of claim 27 in which at least one of said phases is a refractory compound and at least one other phase is a binder metal or alloy.
29. The cutting member of claim 28 in which said re-fractory compound is a transition metal carbide.
30. The cutting member of claim 29 in which said metal carbide is tungsten carbide and said binder metal or alloy is iron, cobalt, nickel or copper.
31. The member of claim 30 wherein said exterior surface comprises one phase of binder metal of about 5 to 20 volume percent and another phase of tungsten carbide particles of about 95 to 80 volume percent, and said core comprises one phase of tungsten carbide particles of about 0 to 60 volume percent and another phase of binder metal of about 100 to 40 volume percent.
32. The member of claim 31 further comprising a bearing steel alloy in said core; and wherein said tungsten carbide particles comprise about 70 to 95 volume percent of said exterior surface and less than about 20 volume percent of said core.
33. In a rolling cutter drill bit of the type having at least one generally frusto-conical cutter rotatably mounted on a bearing shaft, the improvement comprising:
said cutter having at least one cutting element protruding from an external surface thereof;
bearing surface means in the interior of said cutter adapted for co-action with said bearing shaft; and said cutter comprising a densified powder metal-lurgical composite of at least two varying phases, said com-posite having a substantially continuous mechanical property gradient therethrough varying from one mixture of said phases having wear and deformation resistant properties at the ex-terior surface of said cutter to another mixture of said phases having toughness properties in the bearing surface means of said cutter.
said cutter having at least one cutting element protruding from an external surface thereof;
bearing surface means in the interior of said cutter adapted for co-action with said bearing shaft; and said cutter comprising a densified powder metal-lurgical composite of at least two varying phases, said com-posite having a substantially continuous mechanical property gradient therethrough varying from one mixture of said phases having wear and deformation resistant properties at the ex-terior surface of said cutter to another mixture of said phases having toughness properties in the bearing surface means of said cutter.
34. The drill bit of claim 33 wherein said exterior surface comprises one phase of binder metal of about 5 to 30 volume percent and another phase of metal carbide particles of about 95 to 70 volume percent; and said core comprises one phase of metal carbide particles of about 0 to 60 volume percent and another phase of binder metal of about 100 to 40 volume percent.
35. The drill bit of claim 34 further comprising a bearing steel alloy in the region of said bearing surface means, said bearing steel having substantially none of said metal carbide phase therein.
36. The drill bit of claim 34 or claim 35 wherein said metal carbide phase comprises tungsten carbide, said binder metal phase is cobalt, and said cutting element is integrally formed on said cutter.
37. The drill bit of claim 34 or claim 35 wherein said metal carbide phase comprises tungsten carbide, said binder metal phase is cobalt, and said cutting element is formed separately from said cutter and attached thereto.
38. In a rolling cutter tool of the type having at least one rotatable cutter mounted on a bearing shaft, said cutter having a plurality of cutting teeth protruding from the surface thereof and an internal bearing surface in close proximity to said shaft; the improvement comprising:
said cutter comprising a densified powder metal-lurgical composite of at least two varying phases, said composite having a substantially continuous mechanical property gradient therethrough varying from one mixture of said phases having wear and deformation resistant properties at the exterior surface of at least the teeth of said cutter to another mixture of said phases having toughness properties in another portion of said cutter.
said cutter comprising a densified powder metal-lurgical composite of at least two varying phases, said composite having a substantially continuous mechanical property gradient therethrough varying from one mixture of said phases having wear and deformation resistant properties at the exterior surface of at least the teeth of said cutter to another mixture of said phases having toughness properties in another portion of said cutter.
39. The rolling cutter tool of claim 38 in which the powder metallurgical composite cutter comprises:
at least one phase of a metal carbide and at least one other phase of a tough binder metal or alloy;
said wear and deformation resistant mixture on the exterior surface comprising a large volume percent of said metal carbide and a small volume percent of said binder metal or alloy; and said tough mixture in another portion of said cutter comprising a small volume percent of said metal carbide and a large volume percent of said binder metal or alloy.
at least one phase of a metal carbide and at least one other phase of a tough binder metal or alloy;
said wear and deformation resistant mixture on the exterior surface comprising a large volume percent of said metal carbide and a small volume percent of said binder metal or alloy; and said tough mixture in another portion of said cutter comprising a small volume percent of said metal carbide and a large volume percent of said binder metal or alloy.
40. A cutting element for attachment to a rolling cutter which is rotatably mounted on a drill bit, said cutting element comprising:
a root portion adapted for engagement in a bit cutter;
a cutting portion on said root portion adapted to protrude from a bit cutter in a cutting orientation; and wherein said cutting element comprises a portion of substantial thickness comprising a densified powder metal-lurgical composite of at least two varying phases, said composite having a substantially continuous mechanical pro-perty gradient through said cutting portion.
a root portion adapted for engagement in a bit cutter;
a cutting portion on said root portion adapted to protrude from a bit cutter in a cutting orientation; and wherein said cutting element comprises a portion of substantial thickness comprising a densified powder metal-lurgical composite of at least two varying phases, said composite having a substantially continuous mechanical pro-perty gradient through said cutting portion.
41. The cutting element of claim 40 wherein at least one of said phases is a refractory compound and at least one other phase is a binder metal or alloy.
42. The cutting element of claim 41 wherein said re-fractory compound is a transition metal carbide and said binder metal or alloy is iron, cobalt, nickel or copper.
.
.
43. The cutting element of claim 40, 41 or 42 in which said composite gradient varies from one mixture of said phases having wear and deformation resistant properties at one point to another mixture of said phases having toughness properties at another point.
44. The cutting element of claim 40, 41 or 42 in which said composite gradient varies from one mixture of said phases having wear and deformation resistant properties at one sur-face of at least part of said cutting portion to another mix-ture of said phases having toughness properties in another portion thereof.
45. The cutting element of claim 40, 41 or 42 in which said composite gradient varies from one mixture of said phases having wear and deformation resistant properties at the exterior surface of said cutting portion to another mixture of said phases having toughness properties in another part thereof.
46. The cutting element of claim42 wherein said tran-sition metal carbide comprises tungsten carbide with the volume fraction of tungsten carbide comprising:
said one phase ranging from about 0 percent to about 95 percent and the volume fraction of said binder metal or alloy comprising said other phase being from about 100 percent to about 5 percent; and at least part of the surface of said cutting por-tion comprising a large volume fraction of said tungsten car-bide and a small volume fraction of said binder metal or alloy and another portion of said cutting portion comprising a sub-stantially lesser volume fraction of said tungsten carbide and a substantially greater volume fraction of said binder metal or alloy than on said surface portion, with a continuous composition gradient therebetween.
said one phase ranging from about 0 percent to about 95 percent and the volume fraction of said binder metal or alloy comprising said other phase being from about 100 percent to about 5 percent; and at least part of the surface of said cutting por-tion comprising a large volume fraction of said tungsten car-bide and a small volume fraction of said binder metal or alloy and another portion of said cutting portion comprising a sub-stantially lesser volume fraction of said tungsten carbide and a substantially greater volume fraction of said binder metal or alloy than on said surface portion, with a continuous composition gradient therebetween.
47. The cutting element of claim 41, 42 or 46 wherein:
the cutting portion of said cutting element is chisel-shaped;
said one phase is concentrated relative to said other phase at the surface of said cutting portion; and said other phase is more concentrated relative to said one phase in the interior of said cutting element.
the cutting portion of said cutting element is chisel-shaped;
said one phase is concentrated relative to said other phase at the surface of said cutting portion; and said other phase is more concentrated relative to said one phase in the interior of said cutting element.
48. The cutting element of claim 47 comprising in addition;
a vertical planar region comprising a large volume fraction of said one phase and small volume fraction of said other phase extending transversely through the interior of said element.
a vertical planar region comprising a large volume fraction of said one phase and small volume fraction of said other phase extending transversely through the interior of said element.
49. The cutting element of Claim 46 wherein said cutting element has a generally cylindrical base portion with a substantially conical truncated cutting portion.
50. The cutting element of claim 49 wherein said one phase is concentrated relative to said other phase at the outermost end of said cutting portion.
51. The cutting element of claim 49 wherein said one phase is concentrated relative to said other phase along the central longitudinal axis of said cutting element.
52. An insert for use in an insert-type rolling cutter drill bit, said insert comprising:
a geometric base portion for insertion into a matching hole in a drill bit cutter;
a tapered, geometrical cutter portion formed on said base portion and adapted to protrude from said hole in a drill bit cutter;
wherein said insert cutter portion comprises a densified powder metallurgical composite of at least two varying phases; and said composite having one portion in which one phase is present in a large volume fraction relative to the other phase, another portion in which said other phase is present in larger volume fraction relative to said one phase and having a substantially continuous mechanical property gradient therebetween.
a geometric base portion for insertion into a matching hole in a drill bit cutter;
a tapered, geometrical cutter portion formed on said base portion and adapted to protrude from said hole in a drill bit cutter;
wherein said insert cutter portion comprises a densified powder metallurgical composite of at least two varying phases; and said composite having one portion in which one phase is present in a large volume fraction relative to the other phase, another portion in which said other phase is present in larger volume fraction relative to said one phase and having a substantially continuous mechanical property gradient therebetween.
53. The insert of claim 52 wherein said base portion is substantially conical and said one phase comprises a tran-sition metal carbide and said other phase comprises a binder metal or alloy.
54. The insert of claim 52 wherein said base portion is substantially cylindrical and said one phase comprises a transition metal carbide and said other phase comprises a binder metal or alloy.
55. The insert of claim 53 or 54 wherein said tran-sition metal carbide comprises tungsten carbide and said binder metal or alloy is selected from the group of iron, nickel, cobalt and copper.
56. The insert of claims 52, 53, or 54 wherein said one phase of said powder metallurgical composite is concentrated relative to said other phase along the central longitudinal axis of said insert and said other phase is concentrated relative to said one phase near the outer surface of said insert, with a radially oriented gradient therebetween.
57. The insert of claims 52, 53 or 54 wherein the outermost end of said protruding portion of said insert has one phase concentrated relative to the other phase, and the base portion has the other phase concentrated relative to said one phase, with a longitudinal gradient therebetween.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000394430A CA1157606A (en) | 1982-01-19 | 1982-01-19 | Methods of manufacturing gradient composite metallic structures and gradient composite metallic products |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000394430A CA1157606A (en) | 1982-01-19 | 1982-01-19 | Methods of manufacturing gradient composite metallic structures and gradient composite metallic products |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157606A true CA1157606A (en) | 1983-11-29 |
Family
ID=4121856
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000394430A Expired CA1157606A (en) | 1982-01-19 | 1982-01-19 | Methods of manufacturing gradient composite metallic structures and gradient composite metallic products |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1157606A (en) |
-
1982
- 1982-01-19 CA CA000394430A patent/CA1157606A/en not_active Expired
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