Method of Forming a Workpiece
A method of forming a ceramic metal composite workpiece comprises a step of providing a forming assembly with first and second shaping surfaces that together form a chamber. The chamber is shaped substantially similar to a desired external geometry of a green body of the workpiece, and at least one of the surfaces comprises a pressing mechanism adapted to move the surface with respect to the other surface. The method also comprises placing into the chamber a malleable composite material and an insert comprising a shape substantially similar to a desired internal surface geometry of the green body. The method also comprises a step of pressing the malleable composite material to form the green body such that at least a portion of the malleable composite material flows around at least a portion of the insert to form the green body with the desired external and internal surface geometries.
This application is a continuation-in-part of U.S. patent application Ser. No. 12/098,934 which is a continuation of Ser. No. 12/051,689 which is a continuation-in-part of U.S. patent application Ser. No. 12/051,586 which is a continuation of U.S. patent application Ser. No. 12/021,051 which is a continuation-in-part of U.S. patent application Ser. No. 12/021,019 which was a continuation-in-part of U.S. patent application Ser. No. 11/971,965 which is a continuation of U.S. patent application Ser. No. 11/947,644, which was a continuation-in-part of U.S. patent application Ser. No. 11/844,586. U.S. patent application Ser. No. 11/844,586 is a continuation-in-part of U.S. patent application Ser. No. 11/829,761. U.S. patent application Ser. No. 11/829,761 is a continuation-in-part of U.S. patent application Ser. No. 11/773,271. U.S. patent application Ser. No. 11/773,271 is a continuation-in-part of U.S. patent application Ser. No. 11/766,903. U.S. patent application Ser. No. 11/766,903 is a continuation of U.S. patent application Ser. No. 11/766,865. U.S. patent application Ser. No. 11/766,865 is a continuation-in-part of U.S. patent application Ser. No. 11/742,304. U.S. patent application Ser. No. 11/742,304 is a continuation of U.S. patent application Ser. No. 11/742,261. U.S. patent application Ser. No. 11/742,261 is a continuation-in-part of U.S. patent application Ser. No. 11/464,008. U.S. patent application Ser. No. 11/464,008 is a continuation-in-part of U.S. patent application Ser. No. 11/463,998. U.S. patent application Ser. No. 11/463,998 is a continuation-in-part of U.S. patent application Ser. No. 11/463,990. U.S. patent application Ser. No. 11/463,990 is a continuation-in-part of U.S. patent application Ser. No. 11/463,975. U.S. patent application Ser. No. 11/463,975 is a continuation-in-part of U.S. patent application Ser. No. 11/463,962. U.S. patent application Ser. No. 11/463,962 is a continuation-in-part of U.S. patent application Ser. No. 11/463,953. The present application is also a continuation-in-part of U.S. patent application Ser. No. 11/695,672. U.S. patent application Ser. No. 11/695,672 is a continuation-in-part of U.S. patent application Ser. No. 11/686,831. All of these applications are herein incorporated by reference for all that they contain.
BACKGROUND OF THE INVENTIONFormation degradation, such as pavement milling, mining, or excavating, may result in wear on impact resistant picks. Consequently, many efforts have been made to extend the working life of these picks by optimizing the shape of the picks or the materials with which they are made. Examples of such efforts are disclosed in U.S. Pat. No. 4,944,559 to Sionnet et al., U.S. Pat. No. 5,837,071 to Andersson et al., U.S. Pat. No. 5,417,475 to Graham et al., U.S. Pat. No. 6,051,079 to Andersson et al., and U.S. Pat. No. 4,725,098 to Beach, all of which are herein incorporated by reference for all that they contain.
One solution to pick wear resistance includes the use of ceramic metal composite workpiece, such as those constructed from tungsten carbide, other carbides, and/or polycrystalline diamond. U.S. patent application Ser. No. 11/971,965, which is hereby incorporated by reference for all that it contains, was filed on 10 Jan. 2008 by Hall, et al., and was entitled “Pick with interlocked bolster.” This application discloses an embodiment of a carbide bolster comprising a cavity formed in a base end of the bolster and which is interlocked with a rear portion of a pick.
U.S. Pat. No. 3,848,040 to Confer et al., which is herein incorporated by reference for all that it contains, discloses an integrally formed, segmentally removable, composite core means of organic polymer foam and plaster segments. Portions of each of these segments form the external surface of the core means, but the plaster segment or segments form the greater part of such surface that constitutes a cavity-forming surface. This core means cooperates with a vehicle-absorbent mold to define a mold cavity into which is cast a slip of particulate inorganic material in volatile vehicle.
U.S. Pat. Nos. 7,105,111 and 7,011,785, both granted to Bauer et al. and both of which are herein incorporated by reference for all that they contain, disclose processes for producing hollow bodies comprising fibre-reinforced ceramic materials, where cores whose shape corresponds to that of the hollow spaces are produced in a first step.
U.S. Pat. No. 6,274,078 to Dunyak et al., which is herein incorporated by reference for all that it contains, discloses a method of removing a core from a CMC component in which the core was used to form an internal cavity.
U.S. Pat. No. 5,993,725 to Zuk et al., which is herein incorporated by reference for all that it contains, discloses a method of forming hollow bodies of ceramic material suitable for use as the discharge vessels of high intensity discharge lamps that includes forming a fugitive core of substantially pure graphite having a configuration matching the interior configuration of the hollow body.
U.S. Pat. No. 5,255,427 to Hafner, which is herein incorporated by reference for all that it contains, discloses a hollow boy integrally formed of ceramic material and comprising a cavity formed therein and an integral connecting joint including a passage to said cavity at least one side of said cavity being confined by a diaphragm integral thereto.
U.S. Pat. No. 4,834,938 to Pyzik et al., which is herein incorporated by reference for all that it contains, discloses a process for making a composite article without shrinkage, particularly of ceramic and metal wherein the article includes complex internal surfaces or cavities.
BRIEF SUMMARY OF THE INVENTIONIn one aspect of the invention, a method of forming a ceramic metal composite workpiece comprises a step of providing a forming assembly with first and second shaping surfaces that together form a chamber. The chamber is shaped substantially similar to a desired external geometry of a green body of the workpiece, and at least one of the surfaces comprises a pressing mechanism adapted to move the surface with respect to the other surface. The method further comprises a step of placing into the chamber a malleable composite material and an insert comprising a shape substantially similar to a desired internal surface geometry of the green body. The method also comprises a step of pressing the malleable composite material to form the green body such that at least a portion of the malleable composite material flows around at least a portion of the insert to form the green body with the desired external and internal surface geometries.
The method may comprise an additional step of sintering the green body. The green body may be sintered under pressure. During the sintering process the insert may vaporize and/or melt out of the green body. Following sintering the workpiece may be brazed to an impact tip comprising a superhard material disposed on an impact surface of the tip. The step of pressing the malleable composite material may comprise pressing the material with a pressure of at least 5000 psi.
The insert may comprise a vaporization temperature of 600° C. or lower. The insert may comprise a diffusion barrier. The insert may comprise a material selected from the group consisting of plastics, metals, waxes, polymers, or combinations thereof. At least a portion of the insert may have a shape comprising a generally spherical geometry, a generally hourglass-shaped geometry, a generally cone-shaped geometry, or combinations thereof. The insert may comprise at least one ledge, lip, taper, protrusion, ridge, prong, slot, or combinations thereof. The insert may comprise inner and outer diameters, and may comprise a thread form disposed on an outer surface of the insert.
The composite material may comprise a tungsten carbide. In some embodiments the composite material may comprise a polycrystalline diamond. The malleable composite material may comprise a sintering temperature of at least 1300° C.
The green body may comprise a ledge, lip, taper, protrusion, ridge, slot, or combinations thereof. The insert may be placed into the chamber prior to placing the malleable composite material in the chamber. In some embodiments the malleable composite material may be placed into the chamber prior to placing the insert in the chamber. At least one of the shaping surfaces may comprise an insert connection and/or release mechanism.
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The bolster 205 may comprise tungsten, titanium, tantalum, molybdenum, niobium, cobalt, diamond, polycrystalline diamond, and/or combinations thereof. The super hard material 206 may be a material selected from the group consisting of diamond, monocrystalline diamond, polycrystalline diamond, sintered diamond, chemical deposited diamond, physically deposited diamond, natural diamond, infiltrated diamond, layered diamond, thermally stable diamond, silicon-bonded diamond, metal-bonded diamond, silicon carbide, cubic boron nitride, and combinations thereof. In
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A superhard material 206 may comprise a generally conical shape with an apex. A thickness of the diamond at the apex may be 0.100 to 0.500 inches. The cemented metal carbide substrate 207 may comprise a height of 0.090 to 0.250 inches. The superhard material 206 bonded to the substrate 207 may comprise a substantially pointed geometry with an apex comprising a 0.050 to 0.160 inch radius. Preferably, the interface between the substrate 207 and the superhard material 206 is non-planar, which may help distribute loads on the tip 208 across a larger area of the interface. The side wall of the superhard material may form an included angle with a central axis of the tip between 30 to 60 degrees. In asphalt milling applications, the inventors have discovered that an optimal included angle is 45 degrees, whereas in mining applications the inventors have discovered that an optimal included angle is between 35 and 40 degrees. A tip that may be compatible with the present invention is disclosed in U.S. patent application Ser. No. 11/673,634 to Hall and is currently pending.
The impact tip 208 may be brazed onto the carbide bolster 205 at a braze interface. Braze material used to braze the tip 208 to the bolster 205 may comprise a melting temperature from 700 to 1200 degrees Celsius; preferably the melting temperature is from 800 to 970 degrees Celsius. The braze material may comprise silver, gold, copper nickel, palladium, boron, chromium, silicon, germanium, aluminum, iron, cobalt, manganese, titanium, tin, gallium, vanadium, phosphorus, molybdenum, platinum, or combinations thereof. The braze material may comprise 30 to 62 weight percent palladium, preferable 40 to 50 weight percent palladium. Additionally, the braze material may comprise 30 to 60 weight percent nickel, and 3 to 15 weight percent silicon; preferably the braze material may comprise 47.2 weight percent nickel, 46.7 weight percent palladium, and 6.1 weight percent silicon. Active cooling during brazing may be critical in some embodiments, since the heat from brazing may leave some residual stress in the bond between the carbide substrate 207 and the super hard material 206. The farther away the super hard material is from the braze interface, the less thermal damage is likely to occur during brazing. Increasing the distance between the brazing interface and the super hard material 206, however, may increase the moment on the carbide substrate 207 and increase stresses at the brazing interface upon impact.
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Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.
Claims
1. A method of forming a ceramic metal composite workpiece, comprising the steps of:
- providing a forming assembly with first and second shaping surfaces together forming a chamber shaped substantially similar to a desired external geometry of a green body of the workpiece, and at least one of the surfaces comprising a pressing mechanism adapted to move the surface with respect to the other surface;
- placing a malleable composite material and an insert comprising a shape substantially similar to a desired internal surface geometry of the green body within the chamber;
- pressing the malleable composite material to form the green body such that at least a portion of the malleable composite material flows around at least a portion of the insert to form the green body with the desired external and internal surface geometries.
2. The method of claim 1, wherein the method comprises an additional step of sintering the green body.
3. The method of claim 2, wherein the step of sintering is done under pressure.
4. The method of claim 2, wherein the insert vaporizes and/or melts out of the green body during the step of sintering the green body.
5. The method of claim 2, wherein the method further comprises a step of brazing the sintered workpiece to an impact tip comprising a superhard material disposed on an impact surface of the tip.
6. The method of claim 1, wherein the step of pressing the malleable composite material comprises pressing the material with a pressure of at least 5000 psi.
7. The method of claim 1, wherein the insert comprises a vaporization temperature of 600° C. or lower.
8. The method of claim 1, wherein the insert comprises a diffusion barrier.
9. The method of claim 1, wherein the insert comprises an insert material selected from the group consisting of plastics, metals, waxes, polymers, and combinations thereof.
10. The method of claim 1, wherein at least a portion of the insert has a shape comprising a generally spherical geometry, a generally hourglass-shaped geometry, a generally cone-shaped geometry, or combinations thereof.
11. The method of claim 1, wherein the insert comprises at least one ledge, lip, taper, protrusion, ridge, prong, slot, or combinations thereof.
12. The method of claim 1, wherein the insert comprises inner and outer diameters.
13. The method of claim 1, wherein the insert comprises a thread form disposed on an outer surface of the insert.
14. The method of claim 1, wherein the composite material comprises a tungsten carbide.
15. The method of claim 1, wherein the composite material comprises a polycrystalline diamond.
16. The method of claim 1, wherein the malleable composite material comprises a sintering temperature of at least 1300° C.
17. The method of claim 1, wherein the green body comprises a ledge, lip, taper, protrusion, ridge, slot, or combinations thereof.
18. The method of claim 1, wherein the insert is placed into the chamber prior to placing the malleable composite material in the chamber.
19. The method of claim 1, wherein the malleable composite material is placed into the chamber prior to placing the insert in the chamber.
20. The method of claim 1, wherein at least one of the shaping surfaces comprises an insert connection and/or release mechanism.
Type: Application
Filed: Apr 7, 2008
Publication Date: Aug 7, 2008
Inventors: David R. Hall (Provo, UT), Gary Peterson (Provo, UT)
Application Number: 12/099,038
International Classification: B22F 7/06 (20060101);