1. Field of the Invention
The techniques herein relate to wellsite operations. More particularly, techniques herein relate to a polycrystalline diamond cutting (PDC) element usable, for example, in earth boring drill bits for mineral exploration, and particularly for oil and natural gas.
2. Description of the Related Art
Polycrystalline diamond and polycrystalline diamond-like elements are known, for the purposes of this specification, as PDC elements. PDC elements are typically formed from carbon based materials. Another somewhat similar diamond-like material is known as carbonitride (CN) as described in U.S. Pat. No. 5,776,615.
PDC elements are typically formed from a mix of materials processed under high-temperature and high-pressure into a polycrystalline matrix of bonded diamond crystals. PDC elements may be manufactured in a process which uses catalyzing materials during their formation. These catalyzing materials may form a residue which may impose a limit upon the maximum useful operating temperature of a PDC element while in service.
One manufactured form of a PDC element may be a two-layer or multi-layer PDC element where a facing table of polycrystalline diamond material is integrally bonded to a substrate of less hard material, such as cemented tungsten carbide. The PDC element may be in the form of a circular or part-circular tablet, or it may be formed into other shapes suitable for drilling applications or for other applications, such as friction bearings, valve surfaces, indenters, tool mandrels, etc. PDC elements of this type may be used for a wide range of applications where a hard wear and erosion resistant material may be required. PDC elements may also find particular usage in earth boring drill bits, where the substrate of the PDC element may or may not be brazed to a carrier, and this carrier may also typically be cemented tungsten carbide. This configuration for PDC elements may be used in fixed cutter or rolling cutter earth boring bits. These PDC elements may be received in a socket of the drill bit, brazed on a face of the drill bit, or infiltrated in a body of a ‘matrix’ type drill bit. PDC elements may also be fixed to a post in a machine tool for use in machining various non-ferrous materials.
PDC elements may be formed by sintering diamond powder with a suitable binder-catalyzing material in a high-pressure, high-temperature press. Techniques for forming PDC elements are described, for example, in U.S. Pat. No. 3,141,746. In one process for manufacturing PDC elements, diamond powder is applied to the surface of a preformed tungsten carbide substrate incorporating cobalt. The assembly is then subjected to very high temperature and very high pressure in a press. During this process, cobalt migrates from the substrate into the diamond layer (or table) and acts as a binder-catalyzing material, causing the diamond particles to bond to one another with diamond-to-diamond bonding, and also causing the diamond layer to bond to the substrate.
The completed PDC element may have at least one body with a matrix of diamond crystals bonded to each other with many interstices containing a binder-catalyzing material as described above. The diamond crystals may have a first continuous matrix of diamond, with the interstices forming a second continuous matrix of interstices containing the binder-catalyzing material. In addition, there may be a relatively few areas where the diamond-to-diamond growth has encapsulated some of the binder-catalyzing material. These ‘islands’ may not be part of the continuous interstitial matrix of binder-catalyzing material.
In one form, the diamond body may have from about 85% to about 95% of diamond by volume and the binder-catalyzing material may have the other about 5% to about 15% diamond. Such a PDC element may be subject to thermal degradation due to differential thermal expansion between the interstitial cobalt binder-catalyzing material and diamond matrix beginning at temperatures of about 400 degrees C. Upon sufficient expansion, the diamond-to-diamond bonding may be ruptured and cracks and chips may occur.
When used in highly abrasive cutting applications, such as in drill bits, these PDC elements may typically wear or fracture, and there has been a relationship observed between wear resistance of the PDC elements and their impact strength. This relationship may be attributed to the catalyzing material remaining in the interstitial regions among the bonded diamond crystals which contributes to the thermal degradation of the diamond layer.
A portion of this catalyzing material may be preferentially removed from a portion of the working surface in order to form a surface with much higher abrasion resistance without substantially reducing its impact strength. Examples of such PDC elements designed for increased strength characteristic are described in U.S. Pat. Nos. 6,601,662; 6,592,985 and 6,544,308.
Certain types of PDC elements (e.g., diamond structures) may form protruding lips as the cutter drills. These lips may repeatedly form and then break off as the cutter drills into the earth, so as to always present a sharp cutting edge to the formation. However, a certain amount of wear may occur in the cutting element to form the lips.
Various types of PDC elements have become widely used in the oilfield drilling industry over time, and attempts have been made to increase the cutting efficiency of these PDC elements. However, the drilling market has remained competitive and calls for ever higher drilling rates of penetration. The techniques provided herein are designed to provide these and other capabilities.