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Gradient polycrystalline cubic boron nitride materials and tools incorporating such materialsRelated Patent Categories: Stock Material Or Miscellaneous Articles, Composite (nonstructural Laminate), Of Inorganic Material, Metal-compound-containing Layer, Next To Second Metal-compound-containing LayerGradient polycrystalline cubic boron nitride materials and tools incorporating such materials description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050249978, Gradient polycrystalline cubic boron nitride materials and tools incorporating such materials. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is based upon and claims priority on U.S. Provisional Application No. 60/558,836, filed on Apr. 2, 2004, the contents of which are fully incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] The present invention is directed to functionally gradient polycrystalline cubic boron nitride materials, to tools incorporating such materials. [0003] Polycrystalline cubic boron nitride has been used extensively as a cutting surface in various cutting tools. Polycrystalline cubic boron nitride (PCBN) is formed by placing cubic boron nitride grains, a second phase and a binder phase within a refractory metal enclosure and then sintering the enclosure with its contents at high pressure and high temperature (HPHT) conditions for forming the PCBN. PCBN materials may be tailored to either provide better strength, better toughness, better chemical wear, or better thermal stability. However, as the magnitude of any of these properties is increased, the magnitudes of the remaining properties may be decreased. To overcome this problem, PCBN material layers which have been used in cutting tools, have in many instances, been coated with a thin film, such as Al.sub.2O.sub.3 or TiN, which is more chemically and thermally stable than PCBN during severe cutting conditions. These films reduce the initial chemical wear and the mechanical wear of the PCBN. The problem however with these coatings is that they tend to debond, flake off or wear off from the PCBN layer. This is especially prevalent during machining with a coated PCBN layer. SUMMARY OF THE INVENTION [0004] Polycrystalline cubic boron nitride materials are provided as well as tools incorporating such materials. In one exemplary embodiment, a polycrystalline cubic boron nitride material is provided having a first layer of polycrystalline cubic boron nitride formed from cubic boron nitride grains, and a second layer of polycrystalline cubic boron nitride bonded to the first layer, where the second layer is formed from cubic boron nitride grains which are coarser than the cubic boron nitride grains forming the first layer. In a further exemplary embodiment, a third layer of polycrystalline cubic boron nitride is formed from cubic boron nitride grains which are finer than the grains of cubic boron nitride forming the second layer. The second layer may be sandwiched between the first and third layers. Moreover, the first and third layers may be made of the same material. Furthermore, the first and third layers may have the same type of cubic boron nitride and the same second phase compositions. In another exemplary embodiment, the first and third layers may include a ceramic binder phase. [0005] In a further exemplary embodiment, a third layer of polycrystalline cubic boron nitride may be formed from cubic boron nitride grains which are coarser than the grains of cubic boron nitride forming the first layer. With this embodiment, the first layer may be sandwiched between the second and third layers. Furthermore, the second and third layers may include a ceramic second phase and a binder phase. Moreover, the second and third layers may be made of the same material. In addition, the second and third layers may include the same type of cubic boron nitride and the same second phase compositions. With any of the aforementioned exemplary embodiments, at least one of the layers may include a ceramic binder phase. [0006] In another exemplary embodiment, a polycrystalline cubic boron nitride material is provided having a first layer of polycrystalline cubic boron nitride formed from cubic boron nitride grains and a second phase material, and a second layer of polycrystalline cubic boron nitride bonded to the first layer, where the second layer is formed from cubic boron nitride grains having the same size as the grains forming the first layer. The second layer may include a second phase material different from the second phase material of the first layer. In one exemplary embodiment, the first layer includes from about 50% to about 80% by volume cubic boron nitride, a binder phase and a ceramic phase, where at least one of the binder and ceramic phases forms the second phase of the first layer. In a further exemplary embodiment, the second layer includes from about 80% to about 95% by volume cubic boron nitride, a metallic second phase and a binder phase. [0007] In another exemplary embodiment, a friction stir welding tool is provided having a base formed of a first material having cubic boron nitride grains, and a pin extending from the base. In the exemplary embodiment, the pin is formed from a second material including cubic boron nitride grains, where one of the first and second materials includes cubic boron nitride grains that are coarser than the cubic boron nitride grains of the other of the first and second materials. In another exemplary embodiment tool, the first and second materials include cubic boron nitride grains in the range of about 80% to about 95% by volume. In yet a further exemplary embodiment, each of the first and second materials includes at least one of a carbide and a nitride, and at least one of a ceramic and an oxide phase. In another exemplary embodiment, the second material includes cubic boron nitride grains having grain sizes in the range of about 10 microns to about 50 microns, and the first material includes cubic boron nitride grains having grains sizes in the range of about 2 microns to about 30 microns. In a further exemplary embodiment, the first material may include a metallic rich second phase. Furthermore the cubic boron nitride grains of the first material may be coarser than the cubic boron nitride grains of the second material. Alternatively, the cubic boron nitride grains of the first material may be finer than the cubic boron nitride grains of the second material. [0008] In another exemplary embodiment, a friction stir welding tool is provided including a base formed of a first material including cubic boron nitride grains and a second material including cubic boron nitride grains, and a pin extending from the base, the pin formed from the second material, where one of the first and second materials cubic boron nitride grains are coarser than the cubic boron nitride grains of the other of the first and second materials. In a further exemplary embodiment, the base includes a first portion including the first material and a second portion including the second material. The second portion may be a layer adjacent the first portion and the pin may extend from the second portion. The cubic boron nitride grains forming the second material may be coarser than the cubic boron nitride grains forming the first material. The second material may include cubic boron nitride grains in the range of about 80% to about 95% by volume. [0009] In an exemplary embodiment the second material includes at least one of a carbide and a nitride, and at least one of a ceramic and an oxide phase. Furthermore, the second material cubic boron nitride grains may have grain sizes in the range of about 10 microns to about 50 microns, and the first material cubic boron nitride grains may have grain sizes in the range of about 2 microns to about 30 microns. The first material may include cubic boron nitride grains in the range of about 50% to about 80% by volume. [0010] In a further exemplary embodiment, the pin and second portion may be integrally formed and the pin with second portion may be sintered to the first portion. In another exemplary embodiment, the second portion is concentric with the first portion. The first portion may circumferentially surround the second portion, and the pin may extend from the second portion. In yet another exemplary embodiment, the pin may be cylindrical having a diameter. The second portion may also be cylindrical having a diameter. The diameter of the second portion may be greater than the diameter of the pin. In another exemplary embodiment, the diameter of the second portion may be the same as the diameter of the pin. [0011] The first material may have a higher cubic boron nitride content than the first material. The second material may have cubic boron nitride grains in the range of about 80% to about 95% by volume. Furthermore, the second material may included at least one of a carbide and a nitride, and at least one of a ceramic and an oxide phase. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIGS. 1-4 are partial cross-sectional schematic views of exemplary embodiment multilayered PCBN composite material of the present invention. [0013] FIG. 5 is a partial cross-sectional schematic view of an exemplary embodiment compact of the present invention having an exemplary embodiment functionally gradient PCBN composite material over a substrate. [0014] FIG. 6 is a partial cross-sectional schematic view of friction welding apparatus joining two pieces of metal. [0015] FIGS. 7-11 are cross-sectional schematic views of exemplary embodiment friction welding tools incorporating exemplary embodiment functionally gradient PCBN materials according to principles of the present invention. DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION [0016] The present invention provides for functionally gradient polycrystalline cubic boron nitride (PCBN) material and/or material composites which can be tailored for optimal combinations of strength, toughness, chemical wear and thermal stability, to tools incorporating such materials, and to methods of making the same. The exemplary embodiment materials may be used to form, or as part of, cutting tools or other types of tools subjected to wear. [0017] To prepare the functionally gradient PCBN materials, different layers of cBN may be used in particulate form along with a binder. In an exemplary embodiment, any of the layers can be in a high shear compaction (HSCTM) form which is well known in the art and is, for example, described in U.S. Pat. Nos. 5,766,394; 6,193,001 and 6,325,165. In such case, the high shear compaction layers may need to be heated in a vacuum to remove the organic binders. Whether using particulate stock feeds or high shear compaction layer(s), the layers of materials are sealed in an HPHT cell such as a refractory material cell and are subjected to HPHT PCBN sintering conditions for forming the functionally gradient PCBN material. Applicant was able to obtain improved bonding between the PCBN layers when using high shear compaction layers. [0018] Exemplary inventive PCBN material may be formed in a blank which can be cut and ground or finished to a desired shape and dimension. In an alternate exemplary embodiment, a substrate such as a cemented WC--Co substrate may also be added to the cell such that a compact, e.g., a cutting element, is formed having a WC--Co substrate and a functionally gradient layer of PCBN material. In other words, the inventive materials of the present invention may be used as self standing cutting tool materials or may be HPHT sintered on to a cemented WC--Co substrate to form a cutting element or tool. [0019] In one exemplary embodiment, a thin layer of Al.sub.2O.sub.3 is sintered during the HPHT process on to a PCBN matrix resulting in a PCBN layer having increased chemical wear resistance. In an alternate exemplary embodiment, a fine TiCN-rich material and/or a PCBN/TiCN--Al composite is HPHT sintered on to a coarse grain PCBN base achieving increased thermal stability and increased toughness. In yet a further exemplary embodiment, different cubic boron nitride (cBN) grain sizes and second phase materials are mixed for obtaining a PCBN material layer having tailored hardness and toughness. In other exemplary embodiments, including but not limited to the aforementioned exemplary embodiments, coarse cBN grains having a size in the range of about 2 to 30 microns are selected as necessary for obtaining the desired properties. Continue reading about Gradient polycrystalline cubic boron nitride materials and tools incorporating such materials... Full patent description for Gradient polycrystalline cubic boron nitride materials and tools incorporating such materials Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Gradient polycrystalline cubic boron nitride materials and tools incorporating such materials patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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