Cutting elements and bits incorporating the same

This application is a continuation of U.S. application Ser. No. 11/513,292, filed on Aug. 29, 2006, which claims priority and based upon U.S. Provisional Application No. 60/763,624 filed on Jan. 30, 2006, the contents of which are fully incorporated herein be reference.

Cutting elements used in rock bits or other cutting tools typically have a body (i.e., a substrate), which has a contact or interface face. An ultra hard material layer is bonded to the contact face of the body by a sintering process to form a cutting layer, i.e., the layer of the cutting element that is used for cutting. The substrate is generally made from tungsten carbide-cobalt (sometimes referred to simply as “cemented tungsten carbide,” “tungsten carbide” “or carbide”), while the ultra hard material layer is a polycrystalline ultra hard material, such as polycrystalline diamond (“PCD”), polycrystalline cubic boron nitride (“PCBN”) or thermally stable product (“TSP”) material such as thermally stable polycrystalline diamond.

Cemented tungsten carbide is formed by carbide particles being dispensed in a cobalt matrix, i.e., tungsten carbide particles are cemented together with cobalt. To form the substrate, tungsten carbide particles and cobalt are mixed together and then heated to solidify. To form a cutting element having an ultra hard material layer such as a PCD or PCBN hard material layer, diamond or cubic boron nitride (“CBN”) crystals are placed adjacent the cemented tungsten carbide body in a refractory metal enclosure (e.g., a niobium enclosure) and subjected to a high temperature and high pressures so that inter-crystalline bonding between the diamond or CBN crystals occurs forming a polycrystalline ultra hard material diamond or CBN layer. Generally, a catalyst or binder material is added to the diamond or CBN particles to assist in inter-crystalline bonding. The process of heating under high pressure is known as sintering. Metals such as cobalt, iron, nickel, manganese and alike an alloys of these metals have been used as a catalyst matrix material for the diamond or CBN. Various other materials have been added to the diamond crystals, tungsten carbide being one example.

The cemented tungsten carbide may be formed by mixing tungsten carbide particles with cobalt and then heating to form the substrate. In some instances, the substrate may be fully cured. In other instances, the substrate may be not fully cured, i.e., it may be green. In such case, the substrate may fully cure during the sintering process. In other embodiments, the substrate maybe in powder form and may solidify during the sintering process used to sinter the ultra hard material layer.

TSP is typically formed by “leaching” the cobalt from the diamond lattice structure of is polycrystalline diamond. This type of TSP material is sometimes referred to as a “thermally enhanced” material. When formed, polycrystalline diamond comprises individual diamond crystals that are interconnected defining a lattice structure. Cobalt particles are often found within interstitial spaces in the diamond lattice structure. Cobalt has a significantly different coefficient of thermal expansion as compared to diamond, and as such, upon heating of the polycrystalline diamond, the cobalt expands, causing cracking to form in the lattice structure, resulting in the deterioration of the polycrystalline diamond layer. By removing, i.e., by leaching, the cobalt from the diamond lattice structure, the polycrystalline diamond layer because more heat resistant. In another exemplary embodiment, TSP material is formed by forming polycrystalline diamond with a thermally compatible silicon carbide binder instead of cobalt. “TSP” as used herein refers to either of the aforementioned types of TSP materials.

Due to the hostile environment that cutting elements typically operate, cutting elements having cutting layers with improved abrasion resistance, strength and fracture toughness are desired.

In one exemplary embodiment a cutting element is provided having a substrate, a first ultra hard material layer formed over the substrate, and a second ultra hard material layer formed over the first ultra hard material layer. The second ultra hard material layer has a thickness in the range of 0.05 mm to 2 mm. In an exemplary embodiment, the second ultra hard material layer has a higher abrasion resistance than the first ultra hard material layer. In another exemplary embodiment, the second ultra hard material layer has an average ultra hard material particle size that is smaller than an average ultra hard material particle size of the first ultra hard material layer. In yet a further exemplary embodiment, the second ultra hard material layer is a TSP material layer. hi yet another exemplary embodiment, the second ultra hard material layer is a PCD material layer. In a further exemplary embodiment, the second ultra hard material layer is a PCBN material layer. In one exemplary embodiment, the second ultra hard material layer encapsulates the first ultra hard material layer. In yet another exemplary embodiment, the second ultra hard material layer is formed over only a portion of the first ultra hard material layer. In yet a further exemplary embodiment, the first ultra hard material layer has an upper surface and a peripheral surface having a height and the second ultra hard material layer covers between 50% to 100% of the height of the peripheral surface. In a further exemplary embodiment, the thickness of the second ultra hard material layer is not constant. In one exemplary embodiment, a surface of the second ultra hard material layer interfacing with the first ultra hard material layer is non-uniform. In another exemplary embodiment, the first ultra hard material layer has a non-uniform outer surface. In yet another exemplary embodiment, the first and second ultra hard material layers include the same type of ultra hard material In a further exemplary embodiment, the first ultra hard material layer has a depression and the second ultra hard material layer is positioned within the depression. In an exemplary embodiment, the second ultra hard material layer defines a cutting edge of the cutting element to be used for cutting. In yet a further exemplary embodiment, the cutting element further includes a third ultra hard material layer formed over the first ultra hard material layer and spaced apart from the second ultra hard material layer. The third ultra hard material layer has a thickness in the range of 0.05 mm to 2 mm. In yet a further exemplary embodiment, as the second ultra hard material wears it forms a scar exposing the first ultra hard material layer and the second ultra hard material layer defines at least a lip having a sharp edge surrounding said scar. The first ultra hard material layer wears faster than the second ultra hard material layer

In another exemplary embodiment, a drill bit is provided having a body and any of the aforementioned exemplary embodiment cutting element mounted on its body. In a further exemplary embodiment a drill bit is provided having a body and a cutting element mounted on the body. The cutting element includes a substrate and a cutting layer formed over the substrate. The cutting layer includes a first ultra hard material layer formed over the substrate, and a second ultra hard material layer formed over the first ultra hard material layer. The second ultra hard material layer has a thickness in the range of 0.05 mm to 2 mm and is oriented for making contact with an object to be drilled by the bit. In yet another exemplary embodiment, the cutting element cutting layer further includes a third ultra hard material layer formed over the first ultra hard material layer and spaced apart from the second ultra hard material layer. This third ultra hard material layer has a thickness in the range of 0.05 mm to 2 mm. In yet a further exemplary embodiment, the cutting element cutting layer second ultra hard material layer covers the entire first ultra hard material layer.

In another exemplary embodiment, a method for improving the cutting efficiency of a cutting layer is provided. The method includes forming a cutting element having a substrate, a first ultra hard material layer over the substrate and a second ultra hard material layer over the first ultra hard material layer such that the second ultra hard material layer has a thickness in the range of 0.05 mm to 2 mm. The first ultra hard material layer wears faster than the second ultra hard material layer, and the first and second ultra hard material layers define the cutting layer. The method further includes cutting an object with the cutting layer wearing a portion of the second ultra hard material layer exposing a portion of the first ultra hard material layer defining a wear scar exposing the first ultra hard material layer surrounded by the second ultra hard material layer. The method also includes continuing cutting the object with the cutting layer causing the inner layer to wear faster than the outer layer forming at least a lip on the outer layer having a cutting edge surrounding the wear scar. In another exemplary embodiment, the scar has an area that increases after continuous cutting with the cutting layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 are cross-sectional views of exemplary embodiment cutting elements of the present invention.

FIG. 5 is a top view of an exemplary embodiment cutting element of the present invention.

FIGS. 6A, 6B and 7-11 are cross-sectional views of other exemplary embodiment cutting elements of the present invention.

FIG. 12 is a front perspective view of an exemplary embodiment cutting element of the present invention with a portion of its cutting layer worn off.

FIGS. 13A and 13B are cross-sectional views of other exemplary embodiment cutting elements of the present invention.

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Superabrasive materials and compacts, methods of fabricating same, and applications using same
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Polycrystalline diamond compacts, and related methods and applications
Industry Class:
Boring or penetrating the earth

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