A Rigid Composite Structure with a Superhard Interior Surface
A rigid composite structure has a first bore formed in a metallic material and a second bore formed by a super hard interior segment or segments disposed within the first bore. Each segment may be lined adjacent to one another and held under compression within the first bore. The segments may be made of super hard materials such as natural diamond, synthetic diamond, polycrystalline diamond, single crystalline diamond, cubic boron nitrate or other superhard composite materials which exhibit low thermal expansion rates and are generally chemically inert. The resultant rigid composite structure may possess higher tolerances to high pressures and high temperatures within the second bore.
This invention relates to composite structures that retain their structural integrity despite exposure to the wear erosive and/or corrosive effects of sudden high pressures, high-pressure friction forces and high temperatures typically associated with their use, particularly within the interior of the structure. The present invention may be especially adapted for use in gun barrels, piston cylinders, pipes or other composite structures where the retention of structural integrity despite exposure to such brisant forces is an integral component of their ordinary application.
Gun barrels for example, are structures that have typically been constructed of metallic materials that are incorporated to accommodate a projectile or bullet that may then be propelled out of the barrel as a result of an exploding cartridge in the breech end of the structure. During this firing process, brisant forces, including high pressure and elevated temperatures, resulting from the hot gases released from the cartridge and friction and distortion energy created between the bullet and internal circumference of the barrel, are suddenly exerted on the barrel as the bullet travels along and out of the barrel. Gun barrels that are consistently exposed to these brisant forces, such as machine gun barrels that expend hundreds of rounds per minute, are more prone to losing their original structural integrity as the metallic material begins to expand and warp as a result of elevated temperatures exerted on the barrel or the barrel becomes clogged with an accumulation of lead and/or copper that breaks away from projectiles as they exit the barrel. This is of particular concern in gun barrels where the diameter of the barrel expands such that the internal circumference of the barrel no longer holds enough compression to effectively launch a projectile, or the projectile falls short of the desired distance, rendering the gun ineffective. Alternatively, gun barrels have also been known to explode and cause physical injury or death to their operators as a result of deformed, warped or clogged barrels. These concerns have become increasingly significant as advancements have been made in ballistics which have produced higher powered propellants, higher muzzle velocity, higher rates of fire and so forth, making the probability of these phenomena more likely.
In response to these phenomena, many attempts have been made to produce barrels made of tough, high strength materials that can accommodate such advancements and are capable of withstanding the detrimental effects of sudden high pressures and temperatures normally associated in ordinance use. Despite concerted efforts, many of these developments have yet to prove effective in their application because materials that yield high strength characteristics may conversely have very low toughness properties making the barrel brittle and more susceptible to breaking or exploding, while materials that exhibit high toughness properties may conversely exhibit low hardness making them more susceptible to erosion.
BRIEF SUMMARY OF THE INVENTIONThe present invention is a rigid composite structure that is resistant to wear and able to retain its structural integrity when exposed to high temperatures and high pressures. This is achieved through the incorporation of high strength, high toughness crystalline materials and their subsequent structural arrangement. The structural arrangement and selected materials used serve to enhance the structures low co-efficient of thermal expansion, low friction refractory, high hardness, and chemical inert properties which in turn provide better retention of structural integrity and resistance to wear.
The invention comprises a first bore formed in a metallic material. The metallic material may comprise of one or more of the following materials, including; aluminum, titanium, a refractory metal, steel, stainless steel, Invar 36, Invar 42, Invar 365, a composite, a ceramic, carbon fiber or combinations thereof. In some embodiments, the metallic material may exhibit a low co-efficient of thermal expansion. The first bore forms a longitudinal axis and encases segments which form a second bore. The first bore assists to support the segments structurally and may also be shrink wrapped around the segments to hold it under compression.
The super hard geometric segment or segments may be arranged co-axially adjacent one another within the longitudinal axis of the first bore. The segment or segments may comprise natural diamond, synthetic diamond, polycrystalline diamond, single crystalline diamond, cubic boron nitride or composite materials. These materials may have low thermal expansion characteristics and are typically chemically inert which further enhances the structures ability to retain its structural integrity. The segment or segments may remain in place within the longitudinal axis of the first bore being interposed between both a shoulder and biased end of the first bore or by brazing each segment together. The brazed material may comprise of gold, silver, a refractory metal, carbide, tungsten carbide, niobium, titanium, platinum, molybdenum, Nickel Paladiium, cadmium, cobalt, chromium, copper, silicon, Zinc, lead, Manganese, tungsten, platinum or combinations thereof. Alternatively, the segments may be held in place by shrink wrapping the first bore around the segments such that the segments are held under radial compression within the first bore and axial compression along the axis of the first bore.
An intermediate material may serve as a transition layer between the first bore and the segments. The intermediate material may comprise of Invar 36, Invar 42, Invar 365, a composite, a ceramic, a refractory metal, carbon fiber or combinations thereof. The transition layer may also serve as a thermal insulator when wrapped in between the first bore and the segments to reduce thermal expansion of the first bore and assist in maintaining the structural integrity of the composite structure. In order to promote metallurgical bonding between the first bore and the segments, as well as the intermediate material, a binder may be used. The binder may comprise cobalt, nickel, iron, tungsten, tantalum, molybdenum, silicon, niobium, titanium, zirconium, a refractory group metal or combinations thereof.
This new composite structure is capable of withstanding hot, highly corrosive environments while at the same time also being capable of withstanding substantial pressure and structural stresses as a result of continued use and friction, especially within the second bore.
BRIEF DESCRIPTION OF THE DRAWINGS
It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following, more detailed description of embodiments of the apparatus of the present invention, as represented in the Figures is not intended to limit the scope of the invention, as claimed, but is merely representative of various selected embodiments of the invention.
The illustrated embodiments of the invention will best be understood by reference to the drawings, wherein like parts are designated by like numerals throughout. Those of ordinary skill in the art will, of course, appreciate that various modifications to the apparatus described herein may easily be made without departing from the essential characteristics of the invention, as described in connection with the Figures. Thus, the following description of the Figures is intended only by way of example, and simply illustrates certain selected embodiments consistent with the invention as claimed herein.
A significant feature of this invention is the second bore 102 which may be formed in super hard geometric segments 103 which have a super hard interior surface 104. The surface may comprise a suitable composite material including but not limited to natural diamond, synthetic diamond, polycrystalline diamond, single crystalline diamond, or cubic boron nitride. This super hard composite material may also incorporate a binder material comprising of cobalt, niobium, titanium, zirconium, nickel, iron, tungsten, tantalum, molybdenum, silicon, a refractory group metal or combinations thereof which may bind together grains of the super hard composite materials in such a way to form the segments. The interior portion of the segments may thus comprise a region depleted of the binder material. This may be advantageous when the second bore 102 is subjected to high temperatures since the binder material may have a higher thermal expansion rate than the superhard composite material. The super hard geometric segments 103, which may be annular segments, wedge like segments, various geometric shape segments or a combination thereof, may be interposed within the first bore 101 in a concentric array that extend lengthwise along the longitudinal axis 106 of the first bore 101. The super hard composite material may be chemically inert and may possess fracture toughness, thermal shock resistance, tensile strength, and low thermal expansion characteristics all of which may serve to further enhance resistance to wear when high pressures or high temperatures are exerted on the interior surface 104 of the structure. While not limited thereto, polycrystalline diamond may be the preferred composite material and may possess a plurality of grains comprised of a size of 0.1 to 300 microns. The super hard composite material may also have a thermal expansion coefficient of approximately 2 μin/in, but in some embodiments, the thermal expansion coefficient may be 0.1 to 10 μin/in. This is a significant feature as it enhances the structural integrity of the overall structure during periods of high pressure and high temperatures in such applications as a gun barrel, piston cylinder, pipe, tube, or other rigid composite structures that may exert friction on the interior surface. Despite the various forces that may act on the super hard interior surface 104, the second bore 102 is able to retain its structural integrity due in part to the inherent characteristics of the super hard geometric segments 103 disposed within the first bore 101.
The first bore 101 may be formed in a suitable metallic material that exhibits lower coefficients of thermal expansion at lower temperatures and higher coefficients of thermal expansion at higher temperatures such as Invar 365. Other suitable metallic materials that may be used include but are not limited to aluminum, titanium, a refractory metal, steel, stainless steel, Invar 36, Invar 42, a composite, a ceramic, carbon fiber or combinations thereof. These materials may exhibit such characteristics that allow the first bore 101 to be manipulated under high temperature and then shrink wrapped around the second bore 102. This process may be used in order to hold the super hard geometric segments 103 under radial compression of 50-200% of operating pressure and axial compression of 50-200% of proof pressure being achieved through incorporation of a shoulder 105 at the first end 107 of the first bore 101 and biasing unit 108 at the second end 109. Although not limited to, the metallic material may be Invar 365 due to its comparative characteristics with polycrystalline diamond which allow both the first bore 101 and second bore 102 to compliment one another in their utility and to further enhance the structures ability to retain its structural integrity during periods of high pressures and high temperatures.
Although the thickness of the super hard composite material may be comparable to the thickness of the metallic material, it should be noted that in embodiments where the structure comprises a gun barrel, the preferred thickness for the super hard composite material is 0.040 inches to 0.25 inches, while the thickness of the metallic material is 0.25 inches to 0.75 inches. The thicknesses of the materials depends on many factors and any combinations of thickness are covered within the scope of the claims.
In a preferred method for manufacturing super hard geometric segments 103, diamond or cubic boron nitride grains are sintered in a high temperature high pressure press to form the desired shape of the segment. Usually a binder material is used to catalyze the sintering process, a preferred binder material being cobalt, which diffuses under the high pressure and temperature from adjacent material (typically tungsten carbide) also in the press. In such a method, a bond will form between the adjacent tungsten carbide and the sintered diamond.
In some embodiments, the breech receiver 204 will be threaded into place in the breech end 203 after the first bore 101 is sufficiently cooled. In other embodiments, the breech receiver 204 is not threaded, but is placed within the first bore 101 such that it biases the segments against the shoulder 105 of the first end 107, thereby applying an axial compression 111. Then the temperature of the first bore 101 is lowered, shrinking itself around the breech receiver 204 such that the receiver is held in place after cooling and continues to apply axial compression 111 to the segments. In yet other embodiments, axial pressure 111 may be applied by a biasing unit 108 while the first bore 101 is expanded and the biasing unit 108 is then removed after first bore 101 is shrunk and the friction between the first and the segments is enough to provide the axial compression 111.
In some embodiments, the pillar may be lined with a high concentration of binder. In other embodiments a foil, such as a cobalt foil, may be wrapped around the pillar which may help in the diffusion of the binder into the diamond grains. In yet other embodiments a foil may be placed between the diamond grains and the pillar to prevent a creation of a strong bond between the two. Still in some embodiments, the pillar may be made of salt or the pillar may be lined with salt. A salt pillar with a foil of a desired binder wrapped around it may allow the formation of a strong annular segment with an easily removable pillar.
Patterns formed in the interior of other composite structures may also be formed using an EDM. It may be desirable that a piston comprise an anti-rotation protrusion and super hard segments lining the bore of the cylinder comprises a complementary slot coaxial with the piston for the protrusion to travel in.
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 rigid composite structure, comprising:
- a first bore formed in a metallic material and comprising a longitudinal axis;
- a second bore formed by geometric segments comprising a superhard interior surface, the segments being disposed adjacent one another substantially co-axial along the longitudinal axis within at least a portion of the first bore.
2. The structure of claim 1, wherein the superhard interior surface comprises a material selected from the group consisting of natural diamond, synthetic diamond, polycrystalline diamond, single crystalline diamond, cubic boron nitride, and composites thereof.
3. The structure of claim 1, wherein the superhard interior surface comprises region that is depleted of a binder material.
4. The structure of claim 1, wherein the superhard interior surface comprises a binder material selected from the group consisting of cobalt, niobium, titanium, zirconium, nickel, iron, tungsten, tantalum, molybdenum, silicon, a refractory group metal, or combinations thereof.
5. The structure of claim 1, wherein the structure further comprises an intermediate material between the first bore and the geometric segments.
6. The structure of claim 5, wherein the intermediate material is a thermal insulator.
7. The structure of claim 5, wherein the intermediate material is wrapped around the segments.
8. The structure of claim 5, wherein the intermediate material comprises Invar 36, Invar 42, Invar 365, a composite, a ceramic, a refractory metal, carbon fiber or combinations thereof.
9. The structure of claim 1, wherein the metallic material comprises a material selected from the group consisting of aluminum, titanium, a refractory metal, steel, stainless steel, Invar 36, Invar 42, Invar 365, a composite, a ceramic, carbon fiber or combinations thereof.
10. The structure of claim 1, wherein the geometric segments are brazed to one another by an interfacing material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, niobium, titanium, platinum, molybdenum, Nickel Paladiium, cadmium, chromium, copper, silicon, zinc, lead, manganese, tungsten, platinum, or combinations thereof.
11. The structure of claim 1, wherein the geometric segments comprise a non-planar end.
12. The structure of claim 1, wherein the superhard interior surface is made of a plurality of grains comprises a size of 1 to 300 microns.
13. The structure of claim 1, wherein the superhard interior surface is under a radial compression of 50-200% of operating pressure.
14. The structure of claim 13, wherein the radial compression is achieved by heat shrinking the tube around the superhard interior surface.
15. The structure of claim 1, wherein the superhard interior surface is under an axial compression of 50-200% of proof pressure.
16. The structure of claim 15, wherein the axial compression is achieved by providing a shoulder in the first end of the first bore and biasing unit in the second end.
17. The structure of claim 1, wherein the superhard interior surface comprises a thermal expansion coefficient of 0.5 to 10 μin/in.
18. The structure of claim 1, wherein the tube further comprises a port through the first bore and the superhard interior surface.
19. The structure of claim 1, wherein superhard interior surface is polished.
20. The structure of claim 1, wherein the superhard interior surface comprises a geometry formed by electrical discharge machining, abrasive lapping or abrasive grinding.
21. The structure of claim 1, wherein the tube is a piston cylinder, a gun barrel, a tube and/or a pipe.
22. The structure of claim 21, wherein the superhard interior surface is disposed within the gun barrel and comprises rifling with a land and groove or polygonal shape.
23. The structure of claim 22, wherein a free bore of the gun barrel is formed in the superhard interior surface.
24. The structure of claim 22 wherein a throat of the gun barrel is formed in the superhard interior surface.
25. A method for forming a rigid composite structure, comprising:
- providing a structure with a first bore intermediate a first and second end;
- providing a plurality of geometric segments with a superhard interior surface;
- forming a second bore by joining the ends of the segments together;
- thermally expanding the first bore;
- placing the segments within the expanded first bore;
- and shrinking the expanded first bore around the segments by cooling.
26. The method of claim 25, wherein a geometry of the superhard segments is formed by electrical discharge machining, abrasive lapping or abrasive grinding.
Type: Application
Filed: May 4, 2006
Publication Date: Nov 8, 2007
Inventors: David Hall (Provo, UT), Scott Dahlgren (Alpine, UT), Ronald Crockett (Payson, UT), Timothy Duke (Provo, UT), Joshua Sensinger (Provo, UT), Joe Fox (Spanish Fork, UT), Tyson Wilde (Spanish Fork, UT)
Application Number: 11/381,709
International Classification: F41A 21/00 (20060101);