Patent Publication Number: US-2020298375-A1

Title: Drilling tools having matrices with carbide-forming alloys, and methods of making and using same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/993,550, filed Jan. 12, 2016, which claims priority to and the benefit of the filing date of: U.S. Provisional Patent Application No. 62/102,221, filed Jan. 12, 2015; U.S. Provisional Patent Application No. 62/102,240, filed Jan. 12, 2015; and U.S. Provisional Patent Application No. 62/115,930, filed Feb. 13, 2015. Each of these patent applications is incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This invention relates to drilling tools for drilling holes in rocks or other formations, and, more particularly, to drill bits for forming a borehole within a formation. 
     BACKGROUND 
     In an effort to increase drill bit life, coatings have been applied to the abrasive cutting media (e.g., diamonds) within drill bits. The diamond industry conventionally uses CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition) coatings to increase bond strength between the matrix of the bit and the abrasive cutting media (e.g., diamond). Conventionally, the most common coatings are Titanium, Chrome, Silicon, and Nickel. The CVD coatings are chemically applied, causing the metallic or semi-metallic coating to react with the diamond and create a strong carbide coating. Unfortunately, after the CVD coating is exposed to the atmosphere, it often forms an oxide layer on the surface of the coated diamond, limiting and weakening the chemical bonding with the matrix in the infiltration/sintering process. The PVD coatings do not form a carbide bond with the diamond; they only have a mechanical bond with the diamond, which is much weaker. In addition, similar to the CVD coatings, when the PVD coatings are exposed to the atmosphere, they can form an oxide layer on the surface of the coated diamond before forming a bond to the matrix/diamond, preventing a good bond to the matrix. Further, the CVD and PVD coatings are limited by the size of the diamonds; if the diamond is too small, the coatings cannot be applied effectively. 
     Multi-layered coatings have also been used. To apply such coatings, a carbide layer is formed using a CVD coating process, and then another layer is added to create a stronger bond between the carbide and the matrix. This creates a stronger coating, but the process is not economical due to the multi-step nature of the process and the expensive materials needed for the additional layers. For example, formation of multi-layered coatings in a CVD coating process conventionally requires multiple heating operations. In addition, the outermost (additional) layer will still form an oxide, thereby limiting the bond strength. Additionally, the smaller the diamonds within the drill bits, the more expensive and/or difficult to apply the multi-layer coatings become. 
     Thus, there is a need for less costly drill bits that have increased penetration rates and are more resistant to breaking down, thereby decreasing the amount of required rod tripping (due to the longer life of the bits) and increasing the amount of core per shift (due to increased penetration rates). 
     SUMMARY 
     Described herein are drilling tools (e.g., drill bits) having a shank, a crown, and a plurality of abrasive cutting elements. The shank can have a first end and an opposing second end. The crown can extend from the second end of the shank. The crown can have a matrix of hard particulate material, a cutting face, and a crown body between the cutting face and the shank. The plurality of abrasive cutting elements can be dispersed throughout at least a portion of the crown body. The matrix of the crown includes a carbide-forming alloy that is configured to form a direct bond with the hard particulate material of the matrix and to form a direct carbide bond with at least one cutting element of the plurality of abrasive cutting elements. Optionally, the carbide-forming alloy can be chromium, titanium, aluminum, or vanadium. It is contemplated that the carbide-forming alloy can be provided as carbide-forming alloy powder or as carbide-forming fibers (e.g., carbide-forming alloy fibers, carbide-forming metal fibers, or semi-metallic carbide-forming fibers). It is further contemplated that the carbide-forming alloys can be provided within a binder. Optionally, the drilling tool can be an impregnated drilling tool (e.g., an impregnated drill bit). Alternatively, the drilling tool can be a surface-set drilling tool (e.g., a surface-set drill bit) in which the plurality of abrasive cutting elements are secured to and project from the cutting face. In exemplary aspects, the drilling tool can be an all-cast drill bit formed by a conventional casting process. 
     Also described herein are drilling systems that comprise an impregnated drilling tool. Optionally, the drilling systems can have a drill rig, a drill string, and an impregnated drilling tool (e.g., an impregnated drill bit). Alternatively, the drilling systems can have a down-hole motor, a drill string, and an impregnated drilling tool (e.g., impregnated drill bit). The drill string can be configured to be secured to and rotated by the drill rig or down-hole motor, and the drilling tool can be attached to a lower end of the drill string. 
     Also described herein is a method of drilling using an impregnated drilling tool as disclosed herein. The method can comprise the step of using the impregnated drilling tool (e.g., an impregnated drill bit) as disclosed herein to penetrate an earthen formation. Optionally, the method can comprise securing the impregnated drilling tool to a drill string and then rotating the drill string to cause the impregnated drilling tool to penetrate an earthen formation. Optionally, in some aspects, the method can further comprise the step of securing the drill string to a drill rig or down-hole motor and using the drill rig or down-hole motor to rotate the drill string. In some aspects, the method can further comprise the step of retrieving a core sample using the impregnated drilling tool. 
     Also described herein are methods of forming the impregnated drilling tools disclosed herein. The method of forming the impregnated drilling tool (e.g., an impregnated drill bit) can include preparing the matrix of the impregnated drilling tool, dispersing the plurality of abrasive cutting media throughout at least a portion of the matrix, infiltrating the matrix with a binder, and securing the shank to the matrix. In these methods, the carbide-forming alloy of the matrix forms a direct bond with the binder and the hard particulate material of the matrix, and the carbide-forming alloy of the matrix forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. 
     Also described herein are drilling systems having a surface-set drilling tool as disclosed herein. Optionally, the drilling systems can have a drill rig, a drill string, and the surface-set drilling tool (e.g., a surface-set drill bit). Alternatively, the drilling systems can have a down-hole motor, a drill string, and the surface-set drilling tool. The drill string can be configured to be secured to and rotated by the drill rig or down-hole motor, and the drilling tool can be attached to a lower end of the drill string. 
     Also described herein is a method of drilling using the surface-set drilling tools disclosed herein. The method can comprise the step of using a surface-set drilling tool (e.g., a surface-set drill bit) as disclosed herein to penetrate an earthen formation. Optionally, the method can comprise the steps of securing a surface-set drilling tool as disclosed herein to a drill string and then rotating the drill string to cause the surface-set drilling tool to penetrate an earthen formation. Optionally, in some aspects, the method can further comprise the step of securing the drill string to a drill rig or down-hole motor and using the drill rig or down-hole motor to rotate the drill string. In some aspects, the method can further comprise the step of retrieving a core sample using the surface-set drilling tool. 
     Also described herein are methods of forming the surface-set drilling tools disclosed herein. The method of forming the surface-set drilling tool (e.g., surface-set drill bit) can include preparing the matrix of the surface-set drilling tool, infiltrating the matrix with a binder, positioning the plurality of abrasive cutting elements at the cutting face as disclosed herein, and securing the shank to the matrix. In these methods, the carbide-forming alloy of the matrix forms a direct bond with the binder and the hard particulate material of the matrix and forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. 
     Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       DETAILED DESCRIPTION OF THE FIGURES 
       These and other features of the preferred embodiments of the invention will become more apparent in the detailed description in which reference is made to the appended drawings wherein: 
         FIG. 1  is a perspective view of an impregnated drill bit as disclosed herein; 
         FIG. 2  is a cross-sectional view of the impregnated drill bit of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of an impregnated drill bit comprising a plurality of large abrasive cutting elements and a plurality of small abrasive cutting elements as disclosed herein; 
         FIG. 4  is a cross-sectional view of an impregnated drill bit comprising a plurality of large abrasive cutting elements, a plurality of small abrasive cutting elements, and a plurality of fibers as disclosed herein; 
         FIG. 5  is a cross-sectional view of an impregnated drill bit comprising a first portion having a plurality of large abrasive cutting elements and a second portion having a plurality of small abrasive cutting elements as disclosed herein; 
         FIG. 6  is a schematic view of a drilling system comprising an impregnated drill bit as disclosed herein; 
         FIG. 7  is an exemplary surface-set coring drill bit as disclosed herein. 
         FIGS. 8A and 8B  are SEM images of the chemical bonds between a diamond and a drill bit matrix comprising an exemplary carbide-forming alloy and a binder as disclosed herein. 
         FIG. 8C  is an SEM image of a conventional coated diamond. As shown in  FIG. 8C , there is a small gap between the matrix and the diamond such that the diamond is only mechanically held in place (rather than being chemically bonded in place). 
     
    
    
     DETAILED DESCRIPTION 
     The present invention can be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. 
     The following description of the invention is provided as an enabling teaching of the invention in its best, currently known embodiment. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof. 
     As used throughout, the singular forms “a,” “an” and “the” comprise plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a diamond” can comprise two or more such diamonds and reference to “a bond” can comprise two or more such bonds unless the context indicates otherwise. 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect comprises from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     As used herein, the term “natural diamond” refers to an industrial natural diamond that is configured for use in conventional drill bit manufacturing processes. 
     As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance can or can not occur, and that the description comprises instances where said event or circumstance occurs and instances where it does not. 
     The word “or” as used herein means any one member of a particular list and also comprises any combination of members of that list. 
     As used herein the term “longitudinal” means along the length of the drill string. Additionally, as used herein the terms “upper,” “top,” and “above” and “lower” and “below” refer to longitudinal positions on the drill string. The terms “upper,” “top,” and “above” refer to positions nearer the mast and “lower” and “below” refer to positions nearer the drilling tool (e.g., drill bit). 
     As used herein, the term “infiltration” or “infiltrating” involves melting a binder material and causing the molten binder to penetrate into and fill the spaces or pores of a matrix. Upon cooling, the binder can solidify, binding the particles of the matrix together. 
     As used herein, the term “sintering” means the removal of at least a portion of the pores between the particles (which can be accompanied by shrinkage) combined with coalescence and bonding between adjacent particles. 
     Disclosed herein, in exemplary aspects, are drilling tools that comprise a shank, a crown, and a plurality of abrasive cutting elements. The shank can have a first end and an opposing second end. The first end of the shank can be adapted to be secured to a drill string component as further disclosed herein. The crown can extend from the second end of the shank. As further disclosed herein, the crown can comprise: a matrix of hard particulate material and a carbide-forming alloy; a cutting face; and a crown body between the cutting face and the shank. The plurality of abrasive cutting elements can be secured at least partially within the crown body. As further disclosed herein, the carbide-forming alloy forms a direct bond with the hard particulate material of the matrix, and the carbide-forming alloy forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. 
     The drilling tools described herein can be used to cut stone, subterranean mineral deposits, ceramics, asphalt, concrete, and other hard materials. These drilling tools can comprise, for example, core-sampling drill bits, drag-type drill bits, reamers (including reamers with impregnated pads, reamers with broach-style pads, reamers with magnum-style pads, and reamers with premium-style pads as are known in the art), stabilizers, casing or rod shoes, and the like. 
     Impregnated Drilling Tools 
     Described herein with reference to  FIGS. 1-5  is an impregnated drilling tool for effectively and efficiently drilling through a formation. In exemplary aspects, the impregnated drilling tool can have a shank, a crown, and a plurality of abrasive cutting elements. In these aspects, it is contemplated that the plurality of abrasive cutting elements can comprise relatively large cutting elements and/or small cutting elements as further disclosed herein. 
     In exemplary aspects, the abrasive cutting elements can be dispersed in an unorganized arrangement throughout at least a portion of the crown. In these aspects, it is contemplated that the plurality of abrasive cutting elements can be dispersed in an unorganized arrangement throughout at least a portion of the crown. 
     Optionally, it is contemplated that the impregnated drilling tools can comprise relatively large abrasive cutting elements. In use, these relatively large abrasive cutting elements can allow the drilling tool to quickly remove the material of a formation being drilled due to the large depth of cut per revolution associated with the large abrasive cutting elements. Additionally, it is contemplated that the disclosed drilling tools can provide increased longevity by providing additional, sub-surface large abrasive cutting elements that are exposed as the crown of the drill bit wears during drilling. Accordingly, the presence of the relatively large abrasive cutting elements can increase the cutting speed of the drilling tool as well as its durability and longevity. 
     For ease of description, the Figures and the following text illustrate examples of impregnated, core-sampling drill bits, and methods of forming and using such drill bits. One will appreciate in light of the disclosure herein, however, that the disclosed systems, methods, and apparatus can be used with other impregnated drilling and cutting tools, such as those mentioned hereinabove (e.g., reamers, stabilizers, casings, rod shoes, etc.). In exemplary aspects, it is contemplated that the drilling tool can comprise a full-face drill bit. In other exemplary aspects, it is contemplated that the drilling tool can comprise an all-cast drill bit. 
     Referring now to the Figures,  FIGS. 1 and 2  illustrate a perspective view and a cross-sectional view, respectively, of an impregnated drill bit  100 . More particularly,  FIGS. 1 and 2  illustrate an impregnated, core-sampling drill bit  100  with a plurality of abrasive cutting elements  110 , which abrade and cut the material being drilled. As shown in  FIG. 1 , the drill bit  100  can comprise a cutting portion or crown  102 . 
     A backing layer  103  can secure or connect the crown  102  to a shank or blank  104 . 
     As shown in  FIGS. 1 and 2 , the plurality of abrasive cutting elements  110  of the crown  102  can be dispersed within a matrix  114 . As shown by  FIG. 2 , the backing layer  103 , which connects the crown  102  to the shank  104 , can be devoid of abrasive cutting elements. In alternative implementations, the backing layer  103  can comprise abrasive cutting elements. 
     As shown by  FIGS. 1 and 2 , in some optional aspects, the backing layer  103  can comprise pins  105 . The pins  105  can be formed from polycrystalline diamonds, tungsten carbide, or other materials with similar material characteristics. The pins  105  can help maintain the bit gauge and help stabilize the impregnated drill bit  100 . In alternative implementations, the backing layer  103  does not comprise pins  105 . 
     Optionally, the shank  104  can be configured to connect the impregnated drill bit  100  to a component of a drill string. In particular, the upper end of the shank  104  (i.e., the end opposite the end secured to the backing layer  103 ) can comprise a connector  106  to which a reaming shell or other drill string component can be secured. As shown in  FIG. 3 , in one or more implementations the connector  106  can comprise a threaded portion having one or more threads. 
       FIGS. 1 and 2  also illustrate that the drill bit  100  can define an interior space about its central axis for receiving a core sample. Thus, both the crown  102  and the shank  104  can have a generally annular shape defined by an inner surface and outer surface. Accordingly, pieces of the material being drilled can pass through the interior space of the impregnated drill bit  100  and, optionally, up through an attached drill string. The impregnated drill bit  100  can be any size, and therefore, can be used to collect core samples of any size. While the impregnated drill bit  100  can have any diameter and can be used to remove and collect core samples with any desired diameter, the diameter of the impregnated drill bit  100  can range in some implementations from about 1 inch to about 12 inches. Additionally, while the kerf of the impregnated drill bit  100  (i.e., the radius of the outer surface minus the radius of the inner surface) can be any width, it is contemplated that the kerf can optionally range from about ¼ inch to about 6 inches. 
     The crown  102  can be configured to cut or drill the desired materials during the drilling process. The crown  102  can comprise a cutting face  108  and a crown body extending between the backing layer  103  or shank  104  and the cutting face  108 . In particular, the crown  102  of the impregnated drill bit  100  can comprise a plurality of cutting segments  109 . The cutting segments  109  can be separated by waterways  112 . The waterways  112  can allow drilling fluid or other lubricants to flow across the cutting face  108  to help provide cooling during drilling. The waterways  112  can also allow drilling fluid to flush cuttings and debris from the inner surface to the outer surface of the impregnated drill bit  100 . 
     The crown  104  can have any number of waterways  112  that provides the desired amount of fluid/debris flow and also allows the crown  102  to maintain the structural integrity needed for drilling operations. For example,  FIGS. 1 and 2  illustrate that the impregnated drill bit  100  can comprise eight waterways  112 . One will appreciate in light of the disclosure herein that the present invention is not so limited. In additional optional aspects, the impregnated drill bit  100  can comprise as few as one waterway or as many as 20 or more waterways, depending on the desired configuration and the formation to be drilled. Additionally, the waterways  112  can be evenly or unevenly spaced around the circumference of the crown  102 . For instance,  FIG. 1  depicts eight waterways  112  substantially evenly spaced from each other about the circumference of the crown  102 . In alternative implementations, however, the waterways  112  can be staggered or otherwise not evenly spaced. 
     Optionally, the plurality of abrasive cutting elements of the crown  102  can comprise a plurality of relatively large abrasive cutting elements, which can allow the impregnated drill bit  100  to quickly cut soft formation material by removing more material per revolution. As used herein, the term “relatively large” refers to abrasive cutting elements having (i) at least one dimension between about 1.0 millimeter and about 8 millimeters, or more preferably between about 2.5 millimeters and about 5 millimeters, or (ii) having a volume of between about 1 millimeter 3  and about 512 millimeters 3 , or more preferably between about 15.2 millimeters 3  and about 125 millimeters 3 , or (iii) a size between about 5 stones per carat and about 108 stones per carat. The “at least one dimension” of the relatively large abrasive cutting elements can comprise a length, a diameter, a width, a height, or other dimension. 
     The abrasive cutting elements  110  of the drill bit  100  can have varied shapes or combinations thereof, such as, for example, spheres, cubes, cylinders, irregular shapes, or other shapes. The abrasive cutting elements  110  can include one or more of natural diamond, synthetic diamond, polycrystalline diamond, thermally stable diamond, aluminum oxide, silicon carbide, silicon nitride, tungsten carbide, cubic boron nitride, boron carbide, alumina, seeded or unseeded sol-gel alumina, other suitable materials, or combinations thereof. In one or more implementations, the abrasive cutting elements  110  can comprise homogenous polycrystalline diamond materials, such as thermally stable diamonds that do not have a carbide backing. 
       FIG. 2  illustrates that the abrasive cutting elements  110  can be dispersed at the cutting face  108  of the crown  102 . In addition,  FIG. 2  shows that the abrasive cutting elements  110  can be dispersed throughout at least a portion of the crown body (i.e., the portion of the crown  102  between the cutting face  108  and the backing layer  103  or shank  104 ). In other words, the abrasive cutting elements  110  can be embedded within the crown  102  at the cutting face  108 , as well as behind the cutting face  108 . Thus, as the abrasive cutting elements  110  and the matrix  114  on the cutting face  108  wear or erode during a drilling process, the embedded abrasive cutting elements  110  are exposed to replenish the cutting face  108 . Such a configuration can provide versatility in cutting as abrasive cutting elements  110  continue to be available to cut throughout the life of the impregnated drill bit  100 . 
     The abrasive cutting elements  110  can be dispersed throughout at least a portion of the crown  102 . For example,  FIG. 2  illustrates that the abrasive cutting elements  110  can be dispersed substantially entirely throughout the crown  102 . In alternative aspects, the abrasive cutting elements  110  can be dispersed throughout only a portion of the crown  102 . For instance, in some aspects, the abrasive cutting elements  110  can be dispersed only in the portions of the crown  102  proximate the cutting face  108 . In yet further aspects, the abrasive cutting elements  110  can be dispersed only in portions of the crown  102  behind the cutting face  108 . 
     As shown in  FIG. 2 , the abrasive cutting elements  110  can be arranged in the crown  102  in an unorganized arrangement. In additional implementations, the abrasive cutting elements  110  can be randomly dispersed within the crown  102 . Thus, in exemplary aspects, the abrasive cutting elements  110  are not arranged in specific alignments relative to each other or the cutting face  108 . In alternative aspects, the abrasive cutting elements  110  can be aligned in a particular manner so that the cutting properties of the cutting elements are presented in an advantageous position with respect to the cutting face  108 . 
     In any event, as  FIG. 2  illustrates, the abrasive cutting elements  110  can be dispersed substantially homogeneously throughout the crown  102 . In alternative aspects, the abrasive cutting elements  110  can be dispersed heterogeneously throughout the crown  102 . For example, in some aspects, the concentration of abrasive cutting elements  110  can vary throughout any portion of the crown  102 , as desired. In particular, the crown  102  can comprise a gradient of abrasive cutting elements  110 . For instance, the portion of the crown  102  that is closest to the cutting face  108  of the impregnated drill bit  100  can contain a first concentration of abrasive cutting elements  110 , and the concentration of abrasive cutting elements  110  can gradually decrease or increase towards the backing layer  103 . Such an impregnated drill bit  100  can be used to drill a formation that begins with a soft, abrasive, unconsolidated formation, which gradually shifts to a hard, non-consolidated formation. Thus, the dispersal of the abrasive cutting elements  110  in the impregnated drill bit  100  can be customized to the desired formation through which it will be used to drill. 
     As mentioned previously, the abrasive cutting elements can be dispersed within a matrix  114 . The matrix  114  can comprise a hard particulate material, such as, for example, a metal or ceramic. One will appreciate in light of the disclosure herein, that the hard particulate material can comprise a powdered material, such as, for example, a powdered metal or alloy, as well as ceramic compounds. In some exemplary aspects, the hard particulate material can comprise tungsten carbide. As used herein, the term “tungsten carbide” means any material composition that contains chemical compounds of tungsten and carbon, such as, for example, WC, W2C, and combinations of WC and W2C. Thus, tungsten carbide comprises, for example, cast tungsten carbide, sintered tungsten carbide, and macrocrystalline tungsten. In additional or alternative aspects, the hard particulate material can comprise carbide, tungsten, iron, cobalt, and/or molybdenum and carbides, borides, alloys thereof, or any other suitable material. 
     In exemplary aspects, the matrix  114  can comprise a carbide-forming alloy that is configured to form a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. In these aspects, as further described herein, the carbide-forming alloy can be configured to form a direct carbide bond with a binder and/or the hard particulate matter of a matrix as further disclosed herein. Thus, in contrast to conventional matrices, which bond to an infiltrant (binder) but not to the cutting elements (e.g., synthetic diamonds), the carbide-forming alloys disclosed herein will form a bonds with both the infiltrant (binder) and at least a portion of the cutting elements. As further disclosed herein, the plurality of abrasive cutting elements can comprise at least one cutting element that is configured to form a carbide bond with the carbide-forming alloy. Exemplary cutting elements that are capable of forming a carbide bond with the carbide-forming alloy include natural diamond, synthetic diamond, polycrystalline diamond, thermally stable diamond, and the like. However, in exemplary aspects, the plurality of abrasive cutting media can further comprise at least one abrasive cutting element that is not configured to form a carbide bond with the carbide-forming alloy. Thus, it is not required that every cutting element within the drilling tool form a carbide bond with a carbide-forming alloy. 
     With reference to  FIGS. 8A-8B , it is contemplated that the formation of a bond with both the infiltrant and the cutting elements (including formation of a carbide that bonds to the cutting elements) can create a supporting structure that retains the cutting elements (e.g., synthetic diamond cutting elements) for significantly longer than conventional matrices, such as the matrix depicted in  FIG. 8C . More particularly, it is contemplated that the cutting elements can be both chemically and mechanically bonded in place (in contrast to conventional bits, in which cutting elements are merely retained mechanically). The longer each cutting element is retained, the more exposure it will have, and increased exposure can allow for a larger gap between the matrix and the surface of the formation (e.g., rock) being drilled. As the gap between the matrix and the surface of the formation increases, flushing/cooling of the bit improves, thereby increasing the life of the cutting elements (e.g., synthetic diamonds) and the bit. Also, when the cutting elements (e.g., synthetic diamonds) have a sufficient supporting structure, the cutting elements (e.g., synthetic diamonds) can undergo advantageous micro-fracturing, which creates many sharp edges instead of a “wear flat” configuration, thereby increasing the cutting efficiency of the drill bit. 
     More particularly, the carbide-forming alloy, which can optionally be provided as carbide-forming alloy powder or as carbide-forming alloy fibers, has a high energy potential to form a carbide with the carbon from the cutting elements (e.g., diamond). In other words, the carbide-forming alloy can be configured to convert the carbon from the cutting elements to form a carbide. By providing the carbon from the cutting elements with an excess amount of carbide-forming alloy, an intermediate layer of the alloy can form between the carbide and the binder and the hard particulate material of the matrix (e.g., tungsten powder), thereby bonding them all together. Thus, it is contemplated that the carbide-forming alloy is configured to form a carbide bond with the cutting elements (e.g., diamond) and to also form an intermediate metallic layer that bonds to the binder and the hard particulate material of the matrix (e.g., tungsten). In further exemplary aspects, the plurality of abrasive cutting elements can comprise a plurality of diamond cutting elements, and the carbide-forming alloy can be configured to convert the diamond cutting elements to a carbide to form the direct carbide bonds between the carbide-forming alloy and the diamond cutting elements. 
     Thus, the process of forming the disclosed drilling tools can bypass or eliminate the initial coating steps of conventional PVD and CVD processes and instead create a chemically bonded coating in a heating/furnacing operation by utilizing matrix powders and binders that will react with the surface of the cutting elements to chemically form a carbide coating. In exemplary aspects, the matrix powders can contain the carbide-forming alloy(s), and the binder can diffuse the carbide-forming alloy(s) throughout the cutting body, thereby improving the reaction of the surface of the cutting elements to form the carbide coating. 
     It is further contemplated that the disclosed process of forming a direct carbide bond can prevent and/or limit the formation of oxides, which, in conventional drilling tools, can significantly weaken chemical bonds. Thus, the disclosed methods can provide for drilling tools having stronger bonds than conventional drilling tools. More particularly, because the formation of the direct carbide bond between carbide-forming alloy and the cutting elements occurs during in situ heating of the cutting tool (within a furnace) and without the need for multiple heating operations, the disclosed drilling tools are not subject to formation of oxide layers that limit chemical bonding between the matrix powders, binders, and cutting elements. 
     In exemplary aspects, the drilling tool can be infiltrated with a binder that does not comprise a carbide-forming material. Rather, the carbide-forming materials are provided in the matrix. In these aspects, the abrasive cutting elements can be un-coated, and the carbide-forming alloy of the matrix can form direct carbide bonds with the uncoated abrasive cutting elements. Thus, it is understood that the disclosed binders are not needed to form the direct carbide bond between the carbide-forming alloy and the cutting elements. 
     In exemplary aspects, the carbide-forming alloy can optionally comprise chromium. 
     In other exemplary aspects, the carbide-forming alloy can optionally comprise titanium. In additional exemplary aspects, the carbide-forming alloy can optionally comprise aluminum. In further exemplary aspects, the carbide-forming alloy can optionally comprise tantalum. In still further exemplary aspects, the carbide-forming alloy can optionally comprise vanadium. In still further exemplary aspects, the carbide-forming alloy can optionally comprise zirconium. However, it is contemplated that the carbide-forming alloy can optionally comprise other materials, such as, for example and without limitation, silicon, niobium, molybdenum, boron, manganese, tungsten, iron, cobalt, and nickel. Optionally, in some aspects, the carbide-forming alloy can consist of a single material, such as, for example and without limitation, titanium, aluminum, tantalum, vanadium, or zirconium. It is understood that the carbide-forming alloys disclosed herein are typically provided as fine powders that can create a risk of an explosion in oxygen (O 2 ) rich environments. Thus, conventionally, manufacturers of drilling tools do not use carbide-forming alloys in the manufacturing process. 
     Alternatively, in various optional aspects, it is contemplated that the carbide-forming alloys can be provided in the form of a PVD (physical vapor deposition) coating on the large abrasive cutting element (e.g., synthetic diamond). However, in these aspects, it is contemplated that additional safety precautions may be required to prevent exposure to “free” chromium (or other materials) that would be protected from the atmosphere if provided as a carbide-forming alloy powder as disclosed above. 
     Additionally, while not shown in the figures, the crown  102  can also comprise a binder. The binder can comprise copper, zinc, silver, molybdenum, nickel, cobalt, or mixtures and alloys thereof. The binder can bond to the matrix  114  and the abrasive cutting elements  110 , thereby binding the crown  102  together. 
     As mentioned previously, in exemplary aspects, the plurality of abrasive cutting elements  110  within the impregnated drill bit  100  can comprise relatively large abrasive cutting elements. In these aspects, it is contemplated that the drill bit  100  can further comprise a plurality of small abrasive cutting elements. For example,  FIG. 3  illustrates a cross-sectional view of an impregnated drill bit  100   a  that comprises a plurality of small abrasive cutting elements  116  in addition to relatively large abrasive cutting elements  110 . It is contemplated that the small abrasive cutting elements can help the drill bit cut in harder formations where the relatively large abrasive cutting elements cannot cut, thereby preventing the bit from polishing. 
       FIG. 3  shows that the small abrasive cutting elements  116  can be dispersed within a matrix  114  along with the relatively large abrasive cutting elements  110 . The small abrasive cutting elements  116  can cut a formation using abrasion. Thus, the small abrasive cutting elements  116  can allow the impregnated drill bit  100   a  to efficiently cut through harder formations. 
     As used herein, the term “small” refers to abrasive cutting elements having (i) a largest dimension less than about 2 millimeters, or more preferably between about 0.01 millimeters and about 1.0 millimeters, or (ii) having a volume that is less than about 0.75 times the volume of a relatively large abrasive cutting element, or more preferably less than about 0.50 times the volume of a relatively large abrasive cutting media, or (iii) a volume between about 0.001 mm 3  and about 8 mm 3 . 
     The small abrasive cutting elements  116  can have varied shapes or combinations thereof, such as, for example, spheres, cubes, cylinders, irregular shapes, or other shapes. The “largest dimension” of the small abrasive cutting elements  116  can thus comprise a length, a diameter, a width, a height, or other dimension. The small abrasive cutting elements  116  can comprise one or more of natural diamond, synthetic diamond, polycrystalline diamond, thermally stable diamond, aluminum oxide, silicon carbide, silicon nitride, tungsten carbide, cubic boron nitride, boron carbide, alumina, seeded or unseeded sol-gel alumina, other suitable materials, or combinations thereof. In one aspect, the small abrasive cutting elements  116  can comprise single diamond crystals. 
       FIG. 3  illustrates that the small abrasive cutting elements  116  can be dispersed at the cutting face  108  of the crown  102 . In addition,  FIG. 3  shows that the small abrasive cutting elements  116  can be dispersed throughout at least a portion of the crown body (i.e., the portion of the crown  102  between the cutting face  108  and the shank  104 ). In other words, the small abrasive cutting elements  116  can be embedded within the crown  102  at the cutting face  108 , as well as behind the cutting face  108 . Thus, as the relatively large abrasive cutting elements  110 , the small abrasive cutting elements  116 , and the matrix  114  on the cutting face  108  wear or erode during a drilling process, the embedded relatively large abrasive cutting elements  110  and the small abrasive cutting elements  116  can be exposed to replenish the cutting face  108 . Such a configuration can provide versatility in cutting as relatively large abrasive cutting elements  110  and small abrasive cutting elements  116  continue to be available to cut throughout the life of the impregnated drill bit  100   a.    
     The small abrasive cutting elements  116  can be dispersed throughout at least a portion of the crown  102 . For example,  FIG. 3  illustrates that the small abrasive cutting elements  116  can be dispersed substantially entirely throughout the crown  102 . In alternative aspects, the small abrasive cutting elements  116  can be dispersed throughout only a portion of the crown  102 . For instance, in some aspects, the small abrasive cutting elements  116  can be dispersed only in the portions of the crown  102  proximate the cutting face  108 . In yet further aspects, the small abrasive cutting elements  116  can be dispersed only in portions of the crown  102  behind the cutting face  108 . 
     As shown in  FIG. 3 , the small abrasive cutting elements  116  can be arranged in the crown  102  in an unorganized arrangement. In additional implementations, the small abrasive cutting elements  116  can be randomly dispersed within the crown  102 . Thus, in exemplary aspects, the small abrasive cutting elements  116  are not arranged in specific alignments relative to each other or the cutting face  108 . 
     In any event, as  FIG. 3  illustrates, the small abrasive cutting elements  116  can be dispersed homogeneously throughout the crown  102 . In alternative aspects, the small abrasive cutting elements  116  can be dispersed heterogeneously throughout the crown  102 . For example, in some aspects, the concentration of the small abrasive cutting elements  116  can vary throughout any desired portion of the crown  102 , as desired. In particular, the crown  102  can comprise a gradient of small abrasive cutting elements  116 . For instance, the portion of the crown  102  that is closest to the cutting face  108  of the impregnated drill bit  100   a  can contain a first concentration of small abrasive cutting elements  116  and the concentration of small abrasive cutting elements  116  can gradually decrease or increase towards the shank  104 . Such an impregnated drill bit  100   a  can be used to drill a formation that begins with a soft, abrasive, unconsolidated formation, which gradually shifts to a hard, non-consolidated formation. Thus, the dispersal of the relatively large abrasive cutting elements  110  and the small abrasive cutting elements  116  in the impregnated drill bit  100   a  can be customized to the desired formation through which it will be drilling. 
     In exemplary aspects, the abrasive cutting elements  110 ,  110   a  at the cutting face  108  can extend out of the cutting face  108 . In other words, as shown in  FIG. 3 , the abrasive cutting elements  110 ,  110   a  can extend from the crown  102  axially away from the cutting face  108 . The abrasive cutting elements  110 ,  110   a  that extend from the crown  102  can help allow for a quick start-up of a new drilling tool  100 ,  100   a . In alternative aspects, the cutting face  108  does not comprise abrasive cutting elements  110 ,  110   a  that extend out of the cutting face  108 , such as the impregnated drill bit  100  of  FIGS. 1 and 2 . In yet further aspects, the cutting face  108  can comprise other features for aiding in the drilling process, such as for example radial grooves. 
       FIG. 4  illustrates another exemplary impregnated drill bit comprising abrasive cutting elements  110 . In particular,  FIG. 4  illustrates an impregnated drill bit  100   b  that comprises a crown  102  having relatively large abrasive cutting elements  110 , small abrasive cutting elements  116 , and a plurality of fibers  118  dispersed within a matrix  114  of hard particulate material. In particular, the crown  102  of one or more implementations of the present invention can comprise fibers, such as the fibers described in U.S. patent application Ser. No. 11/948,185, filed Nov. 30, 2007, entitled “Fiber-Containing Diamond Impregnated Cutting Tools,” now U.S. Pat. No. 7,695,542, the content of which is hereby incorporated herein by reference in its entirety. In exemplary aspects, the fibers  118  can help control the rate at which the matrix  118  erodes, and thus, the rate at which the abrasive cutting elements (comprising abrasive cutting elements  110 , which can optionally be relatively large abrasive cutting elements, and, optionally, small abrasive cutting elements  116 ) is exposed. 
     The fibers  118  can have varied shapes or combinations thereof, such as, for example, ribbon-like, cylindrical, polygonal, elliptical, straight, curved, curly, coiled, bent at angles, etc. The fibers  118  in the crown  102  of the impregnated drill bit  100   b  can be of any size or combination of sizes, comprising mixtures of different sizes. The fibers  118  can be of any length and have any desired diameter. Optionally, in some aspects, the fibers  118  can be between about 10 microns and about 25,000 microns in length and can have a diameter of between about 1 micron and about 500 microns. In other exemplary aspects, the fibers  118  can be about 150 microns in length and can have a diameter of about 7 microns. 
     The fibers  118  can comprise one or more of carbon fibers, metal fibers (e.g., fibers made of tungsten, tungsten carbide, iron, molybdenum, cobalt, or combinations thereof), glass fibers, polymeric fibers (e.g., fibers made of Kevlar), ceramic fibers (e.g., fibers made of silicon carbide), coated fibers, and/or the like. 
       FIG. 4  illustrates that the fibers  118  can be dispersed at the cutting face  108  of the crown  102 . In addition,  FIG. 4  shows that the fibers  118  can be dispersed throughout at least a portion of the crown body (i.e., the portion of the crown  102  between the cutting face  108  and the shank  104 ). In other words, the fibers  118  can be embedded within the crown  102  at the cutting face  108 , as well as behind the cutting face  108 . 
     The fibers  118  can be dispersed throughout at least a portion of the crown  102 . For example,  FIG. 4  illustrates that the fibers  118  are dispersed substantially entirely throughout the crown  102 . In alternative implementations, the fibers  118  can be dispersed throughout only a portion of the crown  102 . For example, in some aspects, the fibers  118  can be dispersed only in the portions of the crown  102  proximate the cutting face  108 . In yet further aspects, the fibers  118  can be dispersed only in portions of the crown  102  behind the cutting face  108 . 
     As shown in  FIG. 4 , the fibers  118  can be arranged in the crown  102  in an unorganized arrangement. In additional aspects, the fibers  118  can be randomly dispersed within the crown  102 . Thus, in exemplary aspects, the fibers  118  are not arranged in specific alignments relative to each other or the cutting face  108 . 
     Optionally, as  FIG. 4  illustrates, the fibers  118  can be dispersed homogeneously throughout the crown  102 . In alternative aspects, the fibers  118  can be dispersed heterogeneously throughout the crown  102 . For example, in some aspects, the concentration of the fibers  118  can vary throughout any portion of the crown  102 , as desired. In particular, the crown  102  can comprise a gradient of fibers  118 . For example, in one exemplary aspect, the portion of the crown  102  that is closest to the cutting face  108  of the impregnated drill bit  100   b  can contain a first concentration of fibers  118  and the concentration of fibers  118  can gradually decrease or increase towards the shank  104 . 
     As alluded to earlier, the dispersal of the abrasive cutting elements  110 , such as for example and without limitation a plurality of relatively large abrasive cutting elements and/or small abrasive cutting elements  116 , in the disclosed impregnated drill bits can be customized to the desired formation through which it will be drilling. For example,  FIG. 5  illustrates a cross-sectional view of an impregnated drill bit  100   c  with a crown  102  customized for a particular formation. In particular, the portion of the crown  102   a  that is closest to the cutting face  108  of the impregnated drill bit  100   c  contains a plurality of abrasive cutting elements  110 , which can optionally be a plurality of relatively large abrasive cutting media. Additionally, the portion of the crown  102   b  that is closest to the shank  104  of the impregnated drill bit  100   c  can contain a plurality of small abrasive cutting elements  116 . Such an impregnated drill bit  100   c  can be used to drill a formation that begins with a soft, abrasive, unconsolidated formation, which gradually shifts to a hard, non-consolidated formation. 
     In particular, the abrasive cutting elements  110  of the first portion of the crown  102   a  can cut the soft material of the formation allowing the impregnated drill bit  100   c  to penetrate the soft formation relatively quickly. Then the small abrasive cutting elements  116  of the second portion of the crown  102   b  can abrade the harder material of the formation allowing the impregnated drill bit  100   c  to penetrate the harder formation relatively quickly. 
     In alternative aspects, the first portion of the crown  102   a  can comprise small abrasive cutting elements  116 , while the second portion of the crown  102   b  comprises other abrasive cutting elements  110 , which can optionally be relatively large abrasive cutting media. In yet further aspects, one of the first portion  102   a  and the second portion  102   b  of the crown can comprise both relatively large abrasive cutting elements  110  and small abrasive cutting elements  116 . In still further aspects, the impregnated drill bit  100   c  can comprise more than two distinct sections  102   a ,  102   b . For example, the impregnated drill bit  100   c  can comprise three, four, five or more sections each tailored to cut efficiently through different types of formations. 
     Drilling Systems Comprising Impregnated Drilling Tools 
     One will appreciate that the impregnated drilling tools as disclosed herein can be used with almost any type of drilling system to perform various drilling operations. For example,  FIG. 6 , and the corresponding text, illustrate or describe one such drilling system with which the disclosed drilling tools can be used. One will appreciate, however, the drilling system shown and described in  FIG. 6  is only one example of a system with which the disclosed drilling tools can be used. 
     For example,  FIG. 6  illustrates a drilling system  120  that comprises a drill head  122 . The drill head  122  can be coupled to a mast  124  that in turn is coupled to a drill rig  126 . The drill head  122  can be configured to have one or more tubular members  128  coupled thereto. Tubular members can comprise, without limitation, drill rods, casings, reaming shells, and down-the-hole hammers. For ease of reference, the tubular members  128  will be described hereinafter as drill string components. The drill string component  128  can in turn be coupled to additional drill string components  128  to form a drill or tool string  130 . In turn, the drill string  130  can be coupled to an impregnated drill bit  100  as disclosed herein, such as the core-sampling drill bits  100 ,  100   a ,  100   b ,  100   c  as described hereinabove. As alluded to previously, the impregnated drill bit  100  can be configured to interface with the material  132 , or formation, to be drilled. 
     In at least one example, the drill head  122  illustrated in  FIG. 6  can be configured to rotate the drill string  130  during a drilling process. In particular, the drill head  122  can vary the speed at which the drill string  130  rotates. For instance, the rotational rate of the drill head and/or the torque the drill head  122  transmits to the drill string  130  can be selected as desired according to the drilling process. 
     Alternatively, in exemplary aspects, a down-hole motor can be used in place of or in addition to the drill head  122 . Thus, in these aspects, the down-hole motor can be coupled to the mast  124  and can have a drill string  130  (one or more drill string components  128 ) coupled thereto. In operation, the down-hole motor can be configured to rotate the drill string  130  during a drilling process. In particular, the down-hole motor can vary the speed at which the drill string  130  rotates. For instance, the rotational rate of the down-hole motor and/or the torque the down-hole motor transmits to the drill string  130  can be selected as desired according to the drilling process. 
     Furthermore, the drilling system  120  can be configured to apply a generally axial (optionally, downward) force to the drill string  130  to urge the impregnated drill bit  100  into the formation  132  during a drilling operation. For example, the drilling system  120  can comprise a chain-drive assembly that is configured to move a sled assembly relative to the mast  124  to apply the generally axial force to the impregnated drill bit  100  as described above. 
     Thus, one will appreciate in light of the disclosure herein, that the drilling tools of the present invention can be used for any purpose known in the art. For example, an impregnated drill bit  100 ,  100   a ,  100   b ,  100   c  can be attached to the end of the drill string  130 , which is in turn connected to a drilling machine or rig  126 . As the drill string  130  and therefore impregnated drill bit  100  are rotated and pushed by the drilling machine  126 , the drill bit  100  can grind away the materials in the subterranean formations  132  that are being drilled. The core samples that are drilled away can be withdrawn from the drill string  130 . The cutting portion of the drill bit  100  can erode over time because of the grinding action. This process can continue until the cutting portion of a drill bit  100  has been consumed and the drilling string  130  can then be tripped out of the borehole and the drill bit  100  is replaced. 
     In use, it is contemplated that the abrasive cutting elements can be positioned within the impregnated drill bit  100  to promote formation of “comet tails” behind the abrasive cutting elements during rotation of the bit. It is contemplated that such “comet tails” can be formed by the friction and cuttings produced by contact between the bit and the formation being cut. It is contemplated that the “comet tails” can be configured to support the cutting elements and to maximize clearance between the cutting face of the crown and the formation in three dimensions. It is further contemplated that these clearances can reduce friction and heat while creating more space to efficiently flush cuttings, thereby increasing cooling of the cutting face. In combination, these features can improve overall bit performance and increase bit life. In exemplary aspects, the comet tails can be formed on the first layer of cutting elements (closest to the bit face) of the drill bit  100 . In these aspects, it is contemplated that, as the first layer of cutting elements wears down and falls out of the drill bit, the underlying layers of cutting elements are randomly positioned, and the formation of tails cannot be controlled. 
     Methods of Forming Impregnated Drilling Tools 
     Implementations of the present invention also comprise methods of forming impregnated drilling tools, such as impregnated drill bits. The following describes at least one method of forming impregnated drilling tools having abrasive cutting elements. Of course, as a preliminary matter, one of ordinary skill in the art will recognize that the methods explained in detail can be modified to install a wide variety of configurations using one or more components of the disclosed drilling system. For example, in one exemplary method, an impregnated drill bit with relatively large abrasive cutting elements can be produced. In exemplary aspects, the impregnated drill bit can be formed using a conventional casting process, such as, for example, a conventional casting process for producing an all-cast bit. 
     For example, in one aspect, a method of forming an impregnated drill bit can comprise preparing a matrix. Optionally, in one aspect, the step of preparing a matrix can comprise preparing a matrix of hard particulate material. For example, the step of preparing a matrix can comprise preparing a matrix of a powdered material, such as for example tungsten carbide. In additional aspects, the matrix can comprise one or more of the previously described hard particulate materials. In some aspects, the step of preparing a matrix can comprise placing the matrix in a mold. In exemplary aspects, as further disclosed herein, the matrix can further comprise at least one carbide-forming alloy. 
     The mold can be formed from a material that is capable of withstanding the heat to which the matrix will be subjected during a heating process. In exemplary aspects, the mold can be formed from carbon. It is contemplated that the mold can be shaped to form a drilling tool (such as a drill bit) having desired features. In exemplary aspects, the mold can correspond to a core drill bit. 
     Additionally, in further aspects, the method can comprise dispersing a plurality of abrasive cutting elements throughout at least a portion of the matrix. Additionally, the method can comprise dispersing the abrasive cutting elements randomly or in an unorganized arrangement throughout the matrix. 
     In exemplary aspects, the step of dispersing a plurality of abrasive cutting elements can optionally comprise dispersing a plurality of relatively large abrasive cutting elements and/or a plurality of small abrasive cutting elements throughout at least a portion of the matrix. Additionally, the method can comprise dispersing the relatively large and/or small abrasive cutting elements randomly or in an unorganized arrangement throughout the matrix. 
     In further exemplary aspects, the method can further comprise dispersing a plurality of fibers throughout at least a portion of the matrix. In particular, it is contemplated that the method can comprise dispersing carbon fibers randomly or in an unorganized arrangement throughout the matrix. 
     In additional aspects, the method can comprise infiltrating the matrix with a binder. In these aspects, the step of infiltrating the matrix with a binder can comprise heating the binder to a molten state and infiltrating the matrix with the molten binder. For example, in some aspects, the binder can be placed proximate the matrix  114  and the matrix  114  and the binder can be heated to a temperature sufficient to bring the binder to a molten state. In these aspects, the molten binder can infiltrate the matrix  114 . In exemplary aspects, the step of infiltrating the matrix with a binder can comprise heating the matrix  114  and the binder to a temperature of at least 787° F. In exemplary aspects, it is contemplated that the binder (in powder form) can initially be positioned on top of the matrix powder (prior to infiltration). In these aspects, one or more conventional fluxing agents (optionally, in powder form) can be positioned on top of the binder. During the process of forming the drilling tools disclosed herein, it is contemplated that the one or more fluxing agents can be configured to prevent formation of, or remove, oxides. Non-limiting examples of fluxing agents include borates, fused borax, fluoborates, elemental boron, fluorides, chlorides, boric acid, alkalies, wetting agents, water, conventional solvents (e.g., alcohols), and combinations thereof. It is contemplated that the use of such fluxing agents can improve bonding among the hard particulate material, carbide-forming alloys, binder, and cutting elements of the drilling tool and reduce surface tension and promote the free flow of the binder during the infiltration process. 
     As further disclosed herein, in exemplary aspects, the carbide-forming alloy of the matrix can form a direct bond with the binder and the hard particulate material of the matrix and form a direct carbide bond with the plurality of abrasive cutting elements (e.g., synthetic diamond) of the matrix. It is further contemplated that the carbide-forming alloy has a high energy potential to form a carbide bond with the carbon from the abrasive cutting elements (e.g., synthetic diamond). In other words, the carbide-forming alloy can be configured to convert the carbon from the cutting elements to form a carbide. The carbon from the abrasive cutting elements can be provided with an excess amount of the carbide-forming alloy, which in turn can form an intermediate layer of the alloy between the carbide and the binder, thereby bonding them all (the carbide-forming alloy, the carbide, and the binder) together. Thus, it is contemplated that the carbide-forming alloy can form a carbide with the abrasive cutting elements and can also form an intermediate metallic layer that bonds to the binder and the hard particulate material of the matrix (e.g., tungsten). 
     It is further contemplated that the disclosed process of forming a direct carbide bond can prevent and/or limit the formation of oxides, which, in conventional drilling tools, can significantly weaken, or not allow, chemical bonds. Thus, the disclosed methods can provide for drilling tools having stronger bonds than conventional drilling tools. More particularly, because the formation of the direct carbide bond between carbide-forming alloy and the cutting elements occurs during in situ heating of the cutting tool (within a furnace) and without the need for multiple heating operations, the disclosed drilling tools are not subject to formation of oxide layers that limit chemical bonding between the matrix powders, binders, and cutting elements. 
     In exemplary aspects, the drilling tool can be infiltrated with a binder that does not comprise a carbide-forming material. In these aspects, the abrasive cutting elements can be un-coated, and the carbide-forming alloy of the matrix can form direct carbide bonds with the uncoated abrasive cutting elements. That is, the abrasive cutting elements are initially un-coated, and the carbide-forming alloy and binder cooperate to coat the abrasive cutting elements in situ within a furnace. However, it is understood that the disclosed binders are not needed to form the direct carbide bond between the carbide-forming alloy and the cutting elements. It is contemplated that any coating of the abrasive cutting elements would interfere with the required direct carbide bonding between the abrasive cutting elements and the carbide-forming alloy. 
     In exemplary aspects, the binder can comprise copper, zinc, silver, molybdenum, nickel, cobalt, tin, iron, aluminum, silicon, manganese, or mixtures and alloys thereof. It is contemplated that the binder can cool, thereby bonding to portions of the the matrix and abrasive cutting elements, and thereby binding portions of the matrix and abrasive cutting media together. In some aspects, the time and/or temperature of the infiltration process can be increased to allow the binder to fill-up a greater number and greater amount of the pores of the matrix. It is contemplated that this can both reduce the shrinkage during sintering, and increase the strength of the resulting drilling tool. 
     Additionally, in further aspects, the method can comprise securing a shank  104  to the matrix  114 . For example, it is contemplated that the step of securing a shank to the matrix can comprise placing a shank  104  in contact with the matrix  114 . It is further contemplated that a backing layer  103  of additional matrix, binder material, and/or flux (e.g., one or more fluxing agents as disclosed herein) can then be added and placed in contact with the matrix  114  as well as the shank  104  to complete initial preparation of a green drill bit. Once the green drill bit has been formed, it can be placed in a furnace to thereby consolidate the drill bit. Thereafter, the drill bit can be finished through machine processes as desired. 
     Optionally, before, after, or in tandem with the infiltration of the matrix  114 , one or more of the disclosed methods can comprise sintering the matrix  14  to a desired density. As sintering involves densification and removal of porosity within a structure, the structure being sintered can shrink during the sintering process. It is contemplated that a structure can experience linear shrinkage of between 1% and 40% during sintering. As a result, it can be desirable to consider and account for dimensional shrinkage when designing tooling (molds, dies, etc.) or machining features in structures that are less than fully sintered. 
     Accordingly, the schematics and methods described herein provide a number of unique products that can be effective for drilling through both soft and hard formations. Additionally, such products can have an increased drilling penetration rate due to the large abrasive cutting elements. Furthermore, as the abrasive cutting elements can be dispersed throughout the crown, new abrasive cutting elements can be continually exposed during the drilling life of the impregnated drill bit. 
     Surface-Set Drilling Tools 
     Described herein with reference to  FIG. 7  is a surface-set drilling tool for effectively and efficiently drilling through a formation. In exemplary aspects, the surface-set drilling tool can have a shank, a crown, and a plurality of abrasive cutting elements. In exemplary aspects, the abrasive cutting elements can be secured at the cutting face of the drilling tool in the manner of conventional surface-set drilling tools. 
     The surface-set drilling tools described herein can be used to cut stone, subterranean mineral deposits, ceramics, asphalt, concrete, and other soft or hard materials. For ease of description, the Figures and the following text illustrate examples of surface-set, core-sampling drill bits, and methods of forming and using such drill bits. One will appreciate in light of the disclosure herein, however, that the disclosed systems, methods, and apparatus can be used with other surface-set drilling and cutting tools, such as, for example and without limitation, a surface-set reamer or a hybrid surface-set/impregnated reamer. In exemplary aspects, the disclosed surface-set bits can be full-face surface-set bits. In other exemplary aspects, the disclosed surface-set bits can be all-cast surface-set bits. 
     It is contemplated that the abrasive cutting elements at the cutting face can allow the surface-set drill bits to cut effectively and efficiently through softer formations. Thus, it is contemplated that the disclosed surface-set drill bits can cut through softer formations at relatively high cutting speeds. Optionally, the abrasive cutting elements can comprise synthetic diamonds, which fracture and create new cutting edges during drilling operations. This is in contrast to polycrystalline diamonds, which fracture across grain boundaries. 
     Referring now to the Figures,  FIG. 7  illustrates a perspective view of a surface-set drill bit  200 . More particularly,  FIG. 7  illustrates a surface-set, core-sampling drill bit  200  with a plurality of abrasive cutting elements  214  secured to the cutting face of the drill bit. As shown in  FIG. 7 , the drill bit  100   a  can comprise a cutting portion or crown  202 . 
     The drill bit  200  can comprise a shank portion  204  with a first end  208  that is configured to connect the drill bit  200  to a component of a drill string. Optionally, the first end  208  can define a threaded portion configured for engagement with corresponding threads of a component of a drill string. By way of example and not limitation, the shank portion  208  may be formed from steel, another iron-based alloy, or any other material that exhibits acceptable physical properties. Also, the drill bit  200  can have a generally annular shape defined by an inner surface  210  and an outer surface  212 . Thus, the drill bits  200  can define an interior space about its central axis for receiving a core sample. Accordingly, pieces of the material being drilled can pass through the interior space of the drill bit  200  and up through an attached drill string. The drill bit  200  may be any size, and therefore, may be used to collect core samples of any size. While the drill bit  200  may have any diameter and may be used to remove and collect core samples with any desired diameter, the diameter of the drill bit  200  can range in some aspects from about 1 inch to about 12 inches. Similarly, while the kerf of the surface-set drill bit  200  (i.e., the radius of the outer surface minus the radius of the inner surface) can be any width, it is contemplated that the kerf can optionally range from about ¼ inch to about 6 inches. 
     In one aspect, the annular crown  202  can be formed from a hard particulate material infiltrated with a binder as is known in the art. Furthermore, the crown  202  can comprise a plurality of cutting elements  214  that are secured to and project from the cutting face of the crown. In various aspects, the cutting elements can comprise one or more of natural diamonds, synthetic diamonds, polycrystalline diamond or thermally stable diamond products, aluminum oxide, silicon carbide, silicon nitride, tungsten carbide, cubic boron nitride, alumina, seeded or unseeded sol-gel alumina, other suitable materials, or combinations thereof. The cutting elements can have varied shapes or combinations thereof, such as, for example, spherical, cubical, cylindrical, irregular shapes, or other polyhedral shapes. The cutting elements  214  can optionally comprise a plurality of relatively large cutting elements as defined herein, such as for example and without limitation, relatively large synthetic diamonds. Optionally, the cutting elements  214  can comprise a plurality of relatively large cutting elements and a plurality of small cutting elements as defined herein. 
     It is contemplated that the disclosed surface-set bits can have any known configuration. In exemplary aspects, the crown  202  can comprise a plurality of cutting segments that are separated by waterways. The waterways can allow drilling fluid or other lubricants to flow across the cutting face to help provide cooling during drilling. The waterways can also allow drilling fluid to flush cuttings and debris from the inner surface to the outer surface of the surface-set drill bit  200 . 
     In exemplary aspects, the crown  202  can be formed from a matrix of hard particulate material, such as for example, a metal. One will appreciate in light of the disclosure herein, that the hard particulate material may comprise a powdered material, such as for example, a powdered metal or alloy, as well as ceramic compounds. According to some implementations of the present invention the hard particulate material can comprise tungsten carbide. As used herein, the term “tungsten carbide” means any material composition that contains chemical compounds of tungsten and carbon, such as, for example, WC, W2C, and combinations of WC and W2C. Thus, tungsten carbide can comprise, for example, cast tungsten carbide, sintered tungsten carbide, and macrocrystalline tungsten. According to additional or alternative implementations of the present invention, the hard particulate material can comprise carbide, tungsten, iron, cobalt, and/or molybdenum and carbides, borides, alloys thereof, or any other suitable material. 
     The hard particulate material of the crown  202  can be infiltrated with a binder, which can provide the crown with increased wear resistance, thereby increasing the life of the drill bit  200 . The binder can bond to the hard particulate material and the abrasive cutting elements to form the crown  202 . It is contemplated that the binder can provide the crown  202  with increased wear resistance, while also not degrading any surface set cutting elements. 
     The binder can comprise copper, zinc, silver, molybdenum, nickel, cobalt, or mixture and alloys thereof. The binder can bond to the matrix and the cutting elements, thereby binding the crown  202  together. In exemplary aspects, the binder can comprise a binder as disclosed in U.S. Patent Publication No. 2013/0098691, entitled “High-Strength, High-Hardness Binders and Drilling Tools Formed Using the Same,” which is incorporated herein by reference in its entirety. 
     As further described above, the cutting elements can be secured at the cutting face of the crown  202  such that a portion of each cutting element projects from the cutting face. Thus, it is contemplated that the cutting elements can be partially embedded within the crown  202  at the cutting face. 
     In exemplary aspects, the cutting elements can be arranged on the cutting face of the crown  202  in an unorganized arrangement. For example, in these aspects, it is contemplated that the cutting elements can be randomly dispersed at the cutting face of the crown  202 . Thus, in exemplary aspects, the cutting elements are not arranged in specific alignments relative to each other or the cutting face. In alternative aspects, the cutting elements can be aligned in a particular manner so that the cutting properties of the cutting elements are presented in an advantageous position with respect to the cutting face. 
     Optionally, in some aspects, the cutting elements can be dispersed substantially homogeneously at the cutting face of the crown  202 . In alternative aspects, the cutting elements can be dispersed heterogeneously at the cutting face of the crown  202 . 
     In exemplary aspects, the matrix of the crown  202  can comprise a carbide-forming alloy that is configured to form a direct carbide bond with at least one abrasive cutting element of the plurality of cutting elements, such as, for example and without limitation, the relatively large cutting elements described herein. In these aspects, as further described herein, the carbide-forming alloy can be configured to form a direct bond with a binder and/or the hard particulate material of a matrix as disclosed herein. Thus, in contrast to conventional matrices, which bond to an infiltrant (binder) but not to the cutting media (e.g., diamonds), the carbide-forming alloys disclosed herein bond to both the infiltrant (binder) and at least a portion of the cutting elements. As further disclosed herein, the plurality of abrasive cutting elements can comprise at least one cutting element (e.g., natural diamond, synthetic diamond, polycrystalline diamond, thermally stable diamond) that is configured to form a carbide bond with the carbide-forming alloy. However, in exemplary aspects, the plurality of abrasive cutting elements can further comprise at least one abrasive cutting element that is not configured to form a carbide bond with the carbide-forming alloy. Thus, it is not required that every cutting element within the drilling tool form a carbide bond with a carbide-forming alloy. 
     With reference to  FIGS. 8A-8B , it is contemplated that the formation of a bond with both the infiltrant and the cutting elements (including formation of a carbide that bonds to the cutting elements) can create a supporting structure that retains the cutting elements (e.g., synthetic diamond) for significantly longer than conventional matrices, such as the matrix depicted in  FIG. 8C . More particularly, it is contemplated that the cutting elements can be both chemically and mechanically bonded in place (in contrast to conventional bits, in which cutting elements are merely retained mechanically). The longer the diamond (or other cutting element) is retained, the more exposure it will have, and increased exposure can allow for a larger gap between the matrix and the surface of the formation (e.g., rock) being drilled. As the gap between the matrix and the surface of the formation increases, flushing/cooling of the bit improves, thereby increasing the life of the cutting elements (e.g., diamonds) and the bit. Also, when the cutting elements (e.g., diamonds) have a sufficient supporting structure, the cutting elements (e.g., diamonds) can undergo advantageous micro-fracturing, which creates many sharp edges instead of a “wear flat” configuration, thereby increasing the cutting efficiency of the drill bit. 
     More particularly, the carbide-forming alloy, which can optionally be provided as carbide-forming alloy powder or as carbide-forming alloy fibers, has a high energy potential to form a carbide with the carbon from the cutting elements (e.g., diamond). In other words, the carbide-forming alloy can be configured to convert the carbon from the cutting elements to form a carbide. By providing the carbon from the cutting elements with an excess amount of carbide-forming alloy, an intermediate layer of the alloy can form between the carbide and the binder and the hard particulate material of the matrix (e.g., tungsten powder), thereby bonding them all together. Thus, it is contemplated that the carbide-forming alloy is configured to form a carbide bond with the cutting elements (e.g., diamond) and to also form an intermediate metallic layer that bonds to the binder and the hard particulate material of the matrix (e.g., tungsten) while being in the temperature/pressure range that does not significantly graphitize the cutting elements (e.g., diamond). In further exemplary aspects, the plurality of abrasive cutting elements can comprise a plurality of diamond cutting elements, and the carbide-forming alloy can be configured to convert the diamond cutting elements to a carbide to form the direct carbide bonds between the carbide-forming alloy and the diamond cutting elements. 
     It is further contemplated that the disclosed process of forming a direct carbide bond can prevent and/or limit the formation of oxides, which, in conventional drilling tools, can significantly weaken chemical bonds. Thus, the disclosed methods can provide for drilling tools having stronger bonds than conventional drilling tools. More particularly, because the formation of the direct carbide bond between carbide-forming alloy and the cutting elements occurs during in situ heating of the cutting tool (within a furnace) and without the need for multiple heating operations, the disclosed drilling tools are not subject to formation of oxide layers that limit chemical bonding between the matrix powders, binders, and cutting elements. 
     In exemplary aspects, the drilling tool can be infiltrated with a binder that does not comprise a carbide-forming material. Rather, the carbide-forming materials are provided in the matrix. In these aspects, the abrasive cutting elements can be un-coated, and the carbide-forming alloy of the matrix can form direct carbide bonds with the uncoated abrasive cutting elements. Thus, it is understood that the disclosed binders are not needed to form the direct carbide bond between the carbide-forming alloy and the cutting elements. 
     In exemplary aspects, the carbide-forming alloy can optionally comprise chromium. 
     In other exemplary aspects, the carbide-forming alloy can optionally comprise titanium. In additional exemplary aspects, the carbide-forming alloy can optionally comprise aluminum. In further exemplary aspects, the carbide-forming alloy can optionally comprise tantalum. In still further exemplary aspects, the carbide-forming alloy can optionally comprise vanadium. In still further exemplary aspects, the carbide-forming alloy can optionally comprise zirconium. However, it is contemplated that the carbide-forming alloy can optionally comprise other materials, such as, for example and without limitation, silicon, niobium, molybdenum, boron, manganese, tungsten, iron, cobalt, and nickel. Optionally, in some aspects, the carbide-forming alloy can consist of a single material, such as, for example and without limitation, titanium, aluminum, tantalum, vanadium, or zirconium. It is understood that the carbide-forming alloys disclosed herein are typically provided as fine powders that can create a risk of an explosion in oxygen (O 2 ) rich environments. Thus, conventionally, manufacturers of drilling tools do not use carbide-forming alloys in the manufacturing process. 
     Alternatively, in various optional aspects, it is contemplated that the carbide-forming alloys can be provided in the form of a PVD (physical vapor deposition) coating on the diamond (or other abrasive cutting media). However, in these aspects, it is contemplated that additional safety precautions may be required to prevent exposure to “free” chromium (or other materials) that would be protected from the atmosphere if provided as a carbide-forming alloy powder as disclosed above. 
       FIG. 7  further illustrates that, in exemplary aspects, the cutting elements at the cutting face can extend out of the cutting face. In other words, the cutting elements at the cutting face can extend from the crown  202  axially away from the cutting face. The cutting elements can help allow for a quick start-up of a new drill bit  200 . 
     Drilling Systems with Surface-Set Drilling Tools 
     One will appreciate that the surface-set drilling tools (e.g., surface-set drill bits) as disclosed herein can be used with almost any type of drilling system to perform various drilling operations. For example, it is contemplated that the surface-set drilling tools can be used with a drilling system as depicted in  FIG. 6  (with the surface-set drill bit  200  being used in place of the impregnated drill bit  100 ). One will appreciate, however, the drilling system shown and described in  FIG. 6  is only one example of a system with which the disclosed drilling tools can be used. 
     An exemplary, non-limiting drilling system can comprise a drill head. The drill head can be coupled to a mast that in turn is coupled to a drill rig. The drill head can be configured to have one or more tubular members coupled thereto. Tubular members can comprise, without limitation, drill rods, casings, reaming shells, and down-the-hole hammers. For ease of reference, the tubular members will be described hereinafter as drill string components. The drill string component can in turn be coupled to additional drill string components to form a drill or tool string. In turn, the drill string can be coupled to a surface-set drill bit  200  as described hereinabove. As alluded to previously, the surface-set drill bit  200  can be configured to interface with the material, or formation, to be drilled. 
     In at least one example, the drill head can be configured to rotate the drill string during a drilling process. In particular, the drill head can vary the speed at which the drill string rotates. For instance, the rotational rate of the drill head and/or the torque the drill head transmits to the drill string can be selected as desired according to the drilling process. 
     Alternatively, in exemplary aspects, a down-hole motor can be used in place of or in addition to the drill head. Thus, in these aspects, the down-hole motor can be coupled to the mast and can have a drill string (one or more drill string components) coupled thereto. In operation, the down-hole motor can be configured to rotate the drill string during a drilling process. In particular, the down-hole motor can vary the speed at which the drill string rotates. For instance, the rotational rate of the down-hole motor and/or the torque the down-hole motor transmits to the drill string can be selected as desired according to the drilling process. 
     Furthermore, the drilling system can be configured to apply a generally longitudinal downward force to the drill string to urge the surface-set drill bit  200  into the formation during a drilling operation. For example, the drilling system can comprise a chain-drive assembly that is configured to move a sled assembly relative to the mast to apply the generally longitudinal force to the surface-set drill bit  200 . 
     Thus, one will appreciate in light of the disclosure herein, that the surface-set drill bits of the present invention can be used for any purpose known in the art. For example, a surface-set drill bit  200  can be attached to the end of the drill string, which is in turn connected to a drilling machine or rig. As the drill string and therefore surface-set drill bit  200  are rotated and pushed by the drilling machine, the drill bit  200  can grind away the materials in the subterranean formations that are being drilled. The core samples that are drilled away can be withdrawn from the drill string. The cutting portion of the drill bit  200  can erode over time because of the grinding action. This process can continue until the abrasive cutting elements  214  have been consumed and the drilling string can then be tripped out of the borehole and the drill bit  200  is replaced. 
     In use, it is contemplated that the cutting elements can be positioned at the cutting face of the surface-set bit  200  to promote formation of “comet tails” behind the cutting elements during rotation of the bit. It is contemplated that such “comet tails” can be formed by the friction and cuttings produced by contact between the bit and the formation being cut. It is contemplated that the “comet tails” can be configured to support the cutting elements and to maximize clearance between the cutting face of the crown and the formation in three dimensions. It is further contemplated that these clearances can reduce friction and heat while creating more space to efficiently flush cuttings, thereby increasing cooling of the cutting face. In combination, these features can improve overall bit performance and increase bit life. 
     Methods of Forming Surface-Set Drilling Tools 
     Implementations of the present invention also comprise methods of forming surface-set drilling tools, such as, for example and without limitation, surface-set drill bits as disclosed herein. The following describes at least one method of forming surface-set drilling tools. Of course, as a preliminary matter, one of ordinary skill in the art will recognize that the methods explained in detail can be modified to install a wide variety of configurations using one or more components of the disclosed drilling system. In exemplary aspects, the surface-set drill bit can be formed using a conventional casting process, such as a conventional casting process for producing an all-cast surface-set drill bit. 
     For example, in one aspect, a method of forming a surface-set drilling tool (e.g., a surface-set drill bit) can comprise preparing a matrix. Optionally, in one aspect, the step of preparing a matrix can comprise preparing a matrix of hard particulate material. For example, the step of preparing a matrix can comprise preparing a matrix of a powdered material, such as for example tungsten carbide. In additional aspects, the matrix can comprise one or more of the previously described hard particulate materials. In some aspects, the step of preparing a matrix can comprise placing the matrix in a mold. In exemplary aspects, as further disclosed herein, the matrix can further comprise a carbide-forming alloy. 
     The mold can be formed from a material that is capable of withstanding the heat to which the matrix will be subjected during a heating process. In exemplary aspects, the mold can be formed from carbon. It is contemplated that the mold can be shaped to form a drilling tool (e.g., drill bit) having desired features. In exemplary aspects, the mold can correspond to a core drill bit. In exemplary aspects, the step of preparing the matrix can comprise using the mold to define a cutting face of the surface-set drill bit. 
     In additional aspects, the method can comprise infiltrating the matrix with a binder. In these aspects, the step of infiltrating the matrix with a binder can comprise heating the binder to a molten state and infiltrating the matrix with the molten binder. For example, in some aspects, the binder can be placed proximate the matrix, and the matrix and the binder can be heated to a temperature sufficient to bring the binder to a molten state. In these aspects, the molten binder can infiltrate the matrix. In exemplary aspects, the step of infiltrating the matrix with a binder can comprise heating the matrix and the binder to a temperature of at least 787° F. In exemplary aspects, it is contemplated that the binder (in powder form) can initially be positioned on top of the matrix powder (prior to infiltration). In these aspects, one or more conventional fluxing agents (optionally, in powder form) can be positioned on top of the binder. During the process of forming the drilling tools disclosed herein, it is contemplated that the one or more fluxing agents can be configured to prevent formation of, or remove, oxides. Non-limiting examples of fluxing agents include borates, fused borax, fluoborates, elemental boron, fluorides, chlorides, boric acid, alkalies, wetting agents, water, conventional solvents (e.g., alcohols), and combinations thereof. It is contemplated that the use of such fluxing agents can improve bonding among the hard particulate material, carbide-forming alloys, binder, and cutting elements of the drilling tool and reduce surface tension and promote the free flow of the binder during the infiltration process. 
     Additionally, in further aspects, the method can comprise securing the plurality of abrasive cutting elements to the cutting face defined by the matrix. Additionally, the method can comprise dispersing the cutting elements randomly or in an unorganized arrangement at the cutting face of the matrix. In exemplary aspects, each cutting medium can be set within a plot mark defined by a mold in a conventional manner. Optionally, in additional exemplary aspects, it is contemplated that the steps of preparing the matrix, infiltrating the matrix, securing the plurality of abrasive cutting media, and securing the shank can be performed using a casting process. 
     When the plurality of cutting media are secured to the cutting face, it is contemplated that the cutting elements can be set at the cutting face (e.g., within a plot mark defined by a mold) in any desired orientation. 
     As further disclosed herein, in exemplary aspects, the carbide-forming alloy of the matrix can form a direct bond with the binder and the hard particulate material of the matrix and form a direct carbide bond with the plurality of abrasive cutting elements (e.g., synthetic diamond) of the matrix. It is further contemplated that the carbide-forming alloy has a high energy potential to form a carbide with the carbon from the cutting elements (e.g., diamond). In other words, the carbide-forming alloy can be configured to convert the carbon from the cutting elements to form a carbide. The carbon from the cutting elements (e.g., diamond) can be provided with an excess amount of the carbide-forming alloy, which in turn can form an intermediate layer of the alloy between the carbide and the binder, thereby bonding them all (the carbide-forming alloy, the carbide, and the binder) together. Thus, it is contemplated that the carbide-forming alloy can form a carbide with the cutting elements (e.g., diamond) and can also form an intermediate metallic layer that bonds to the binder and the hard particulate material of the matrix (e.g., tungsten). 
     It is further contemplated that the disclosed process of forming a direct carbide bond can prevent and/or limit the formation of oxides, which, in conventional drilling tools, can significantly weaken chemical bonds. Thus, the disclosed methods can provide for drilling tools having stronger bonds than conventional drilling tools. More particularly, because the formation of the direct carbide bond between carbide-forming alloy and the cutting elements occurs during in situ heating of the cutting tool (within a furnace) and without the need for multiple heating operations, the disclosed drilling tools are not subject to formation of oxide layers that limit chemical bonding between the matrix powders, binders, and cutting elements. 
     In exemplary aspects, the drilling tool can be infiltrated with a binder that does not comprise a carbide-forming material. In these aspects, the abrasive cutting elements can be un-coated, and the carbide-forming alloy can form direct carbide bonds with the uncoated abrasive cutting elements. That is, the abrasive cutting elements are initially un-coated, and the carbide-forming alloy and binder cooperate to coat the abrasive cutting elements in situ within a furnace. However, it is understood that the disclosed binders are not needed to form the direct carbide bond between the carbide-forming alloy and the cutting elements. It is contemplated that any coating of the abrasive cutting elements would interfere with the required direct carbide bonding between the abrasive cutting elements and the carbide-forming alloy. 
     In exemplary aspects, the binder can comprise copper, zinc, silver, molybdenum, nickel, cobalt, tin, iron, aluminum, silicon, manganese, or mixtures and alloys thereof. It is contemplated that the binder can cool, thereby bonding to the matrix and abrasive cutting media, and thereby binding the matrix and abrasive cutting media together. In some aspects, the time and/or temperature of the infiltration process can be increased to allow the binder to fill-up a greater number and greater amount of the pores of the matrix. It is contemplated that this can both reduce the shrinkage during sintering, and increase the strength of the resulting drilling tool. 
     Additionally, in further aspects, the method can comprise securing a shank  204  to the matrix of the crown  202 . For example, it is contemplated that the step of securing a shank to the matrix can comprise placing a shank  204  in contact with the matrix. It is further contemplated that a backing layer of additional matrix, binder material, and/or flux (e.g., one or more fluxing agents as disclosed herein) can optionally be added and placed in contact with the matrix as well as the shank  204  to complete initial preparation of a green drill bit. Once the green drill bit has been formed, it can be placed in a furnace to thereby consolidate the drill bit. Thereafter, the drill bit can be finished through machine processes as desired. 
     Optionally, before, after, or in tandem with the infiltration of the matrix, one or more of the disclosed methods can comprise sintering the matrix to a desired density. As sintering involves densification and removal of porosity within a structure, the structure being sintered can shrink during the sintering process. It is contemplated that a structure can experience linear shrinkage of between 1% and 40% during sintering. As a result, it can be desirable to consider and account for dimensional shrinkage when designing tooling (molds, dies, etc.) or machining features in structures that are less than fully sintered. 
     Exemplary Aspects 
     In view of the described drilling tools, drilling systems, and methods and variations thereof, herein below are described certain more particularly described aspects of the invention. These particularly recited aspects should not however be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein, or that the “particular” aspects are somehow limited in some way other than the inherent meanings of the language literally used therein. 
     Aspect 1: A drilling tool, comprising: a shank having a first end and an opposing second end, the first end being adapted to be secured to a drill string component; a crown extending from the second end of the shank, the crown comprising a matrix of hard particulate material and a carbide-forming alloy, a cutting face, and a crown body between the cutting face and the shank; and a plurality of abrasive cutting elements secured at least partially within the crown body, wherein the carbide-forming alloy forms a direct bond with the hard particulate material of the matrix, and wherein the carbide-forming alloy forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. 
     Aspect 2: The drilling tool as recited in aspect 1, wherein the carbide-forming alloy comprises chromium. 
     Aspect 3: The drilling tool as recited in aspect 1, wherein the carbide-forming alloy comprises titanium. 
     Aspect 4: The drilling tool as recited in aspect 1, wherein the carbide-forming alloy comprises aluminum. 
     Aspect 5: The drilling tool as recited in aspect 1, wherein the carbide-forming alloy comprises vanadium. 
     Aspect 6: The drilling tool as recited in aspect 1, wherein the plurality of abrasive cutting elements comprises a plurality of synthetic diamonds. 
     Aspect 7: The drilling tool as recited in aspect 1, wherein the plurality of abrasive cutting elements comprises a plurality of thermally stable polycrystalline diamonds. 
     Aspect 8: The drilling tool as recited in aspect 1, wherein the plurality of abrasive cutting elements comprises natural diamond. 
     Aspect 9: The drilling tool as recited in aspect 1, wherein the crown has an annular shape, a longitudinal axis, an inner surface, and an outer surface, wherein the inner surface of the crown defines an interior space about the longitudinal axis, and wherein the interior space is configured to receive a core sample. 
     Aspect 10: The drilling tool as recited in aspect 1, wherein at least one abrasive cutting element of the plurality of abrasive cutting elements extends outwardly from the cutting face. 
     Aspect 11: The drilling tool as recited in aspect 1, wherein the hard particulate material of the matrix of the crown comprises at least one of tungsten and tungsten carbide. 
     Aspect 12: The drilling tool as recited in aspect 1, wherein the drilling tool is a drill bit. 
     Aspect 13: The drilling tool as recited in aspect 12, wherein the drill bit is a full-face drill bit. 
     Aspect 14: The drilling tool as recited in aspect 12, wherein the drill bit is an all-cast drill bit. 
     Aspect 15: The drilling tool as recited in aspect 1, wherein the drilling tool is a reamer. 
     Aspect 16: The drilling tool as recited in aspect 1, wherein the drilling tool is an impregnated drilling tool, and wherein the plurality of abrasive cutting elements are dispersed throughout at least a portion of the crown body. 
     Aspect 17 The drilling tool as recited in aspect 16, wherein the impregnated drilling tool is an impregnated drill bit. 
     Aspect 18: The drilling tool as recited in aspect 16, wherein at least a portion of the plurality abrasive cutting elements are dispersed within the crown body proximate the cutting face. 
     Aspect 19: The drilling tool as recited in aspect 16, further comprising a plurality of fibers dispersed in an unorganized arrangement throughout at least a portion of the crown body. 
     Aspect 20: The drilling tool as recited in aspect 1, wherein the drilling tool is a surface-set drilling tool, and wherein the plurality of abrasive cutting elements are secured to and project from the cutting face of the crown. 
     Aspect 21: The drilling tool as recited in aspect 16, wherein the surface-set drilling tool is a surface-set drill bit. 
     Aspect 22: The drilling tool as recited in aspect 1, wherein the plurality of abrasive cutting elements comprises at least one abrasive cutting element that is not configured to form a carbide bond with the carbide-forming alloy. 
     Aspect 23: The drilling tool as recited in aspect 1, wherein the drilling tool is infiltrated with a binder, and wherein the binder does not comprise a carbide-forming material. 
     Aspect 24: The drilling tool as recited in aspect 23, wherein the abrasive cutting elements are not coated, and wherein the carbide-forming alloy forms direct carbide bonds with the uncoated abrasive cutting elements. 
     Aspect 25: The drilling tool as recited in aspect 1, wherein the plurality of abrasive cutting elements comprise a plurality of diamond cutting elements, and wherein the carbide-forming alloy is configured to convert the diamond cutting elements to a carbide to form the direct carbide bonds between the carbide-forming alloy and the diamond cutting elements. 
     Aspect 26: A drilling system, comprising: a drill string configured for rotation; and a drilling tool, wherein the drilling tool comprises: a shank having a first end and an opposing second end, the first end being adapted to be secured to a drill string component; a crown extending from the second end of the shank, the crown comprising a matrix of hard particulate material and a carbide-forming alloy, a cutting face, and a crown body between the cutting face and the shank; and a plurality of abrasive cutting elements secured at least partially within the crown body, wherein the carbide-forming alloy forms a direct bond with the hard particulate material of the matrix, and wherein the carbide-forming alloy forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. 
     Aspect 27: The drilling system as recited in aspect 26, further comprising a drill rig, wherein the drill string is adapted to be secured to and rotated by the drill rig. 
     Aspect 28: The drilling system as recited in aspect 26, further comprising a down-hole motor, wherein the drill string is adapted to be secured to and rotated by the down-hole motor. 
     Aspect 29: The drilling system as recited in aspect 26, wherein the drilling tool is infiltrated with a binder, and wherein the binder does not comprise a carbide-forming material. 
     Aspect 30: The drilling system as recited in aspect 29, wherein the abrasive cutting elements are not coated, and wherein the carbide-forming alloy forms direct carbide bonds with the uncoated abrasive cutting elements. 
     Aspect 31: The drilling system as recited in aspect 26, wherein the plurality of abrasive cutting elements comprise a plurality of diamond cutting elements, and wherein the carbide-forming alloy is configured to convert the diamond cutting elements to a carbide to form the direct carbide bonds between the carbide-forming alloy and the diamond cutting elements. 
     Aspect 32: A method of drilling, comprising: securing a drilling tool to a drill string, wherein the drilling tool comprises: a shank having a first end and an opposing second end, the first end being adapted to be secured to a drill string component; a crown extending from the second end of the shank, the crown comprising a matrix of hard particulate material and a carbide-forming alloy, a cutting face, and a crown body between the cutting face and the shank; and a plurality of abrasive cutting elements secured at least partially within the crown body, wherein the carbide-forming alloy forms a direct bond with the hard particulate material of the matrix, and wherein the carbide-forming alloy forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements; and rotating the drill string to cause the drilling tool to penetrate an earthen formation. 
     Aspect 33: The method as recited in aspect 32, further comprising securing the drill string to a drill rig and using the drill rig to rotate the drill string. 
     Aspect 34: The method as recited in aspect 32, further comprising securing the drill string to a down-hole motor and using the down-hole motor to rotate the drill string. 
     Aspect 35: The method as recited in aspect 32, wherein the drilling tool is infiltrated with a binder, and wherein the binder does not comprise a carbide-forming material. 
     Aspect 36: The method as recited in aspect 35, wherein the abrasive cutting elements are not coated, and wherein the carbide-forming alloy forms direct carbide bonds with the uncoated abrasive cutting elements. 
     Aspect 37: The method as recited in aspect 32, wherein the plurality of abrasive cutting elements comprise a plurality of diamond cutting elements, and wherein the carbide-forming alloy is configured to convert the diamond cutting elements to a carbide to form the direct carbide bonds between the carbide-forming alloy and the diamond cutting elements. 
     Aspect 38: A method of forming a drilling tool, comprising: preparing a matrix of the drilling tool, the matrix comprising hard particulate material and a carbide-forming alloy; securing a plurality of abrasive cutting elements within at least a portion of the matrix; infiltrating the matrix with a binder; and securing a shank to the matrix, wherein the carbide-forming alloy of the matrix forms a direct bond with the binder and the hard particulate material of the matrix, and wherein the carbide-forming alloy of the matrix forms a direct carbide bond with at least one abrasive cutting element of the plurality of abrasive cutting elements. 
     Aspect 39: The method as recited in aspect 38, wherein the drilling tool is formed using a casting process. 
     Aspect 40: The method as recited in aspect 38, wherein the drilling tool is an impregnated drilling tool, and wherein the plurality of abrasive cutting elements are dispersed throughout at least a portion of the matrix. 
     Aspect 41: The method as recited in aspect 38, wherein the drilling tool is a surface-set drilling tool, wherein the step of preparing the matrix comprises defining a cutting face of the surface-set drilling tool, and wherein the plurality of abrasive cutting elements are secured to the cutting face such that the abrasive cutting elements project from the cutting face. 
     Aspect 42: The method as recited in aspect 38, wherein the binder does not comprise a carbide-forming material. 
     Aspect 43: The method as recited in aspect 42, wherein the abrasive cutting elements are not coated, and wherein the carbide-forming alloy forms direct carbide bonds with the uncoated abrasive cutting elements. 
     Aspect 44: The method as recited in aspect 38, wherein the plurality of abrasive cutting elements comprise a plurality of diamond cutting elements, and wherein the carbide-forming alloy converts the diamond cutting elements to a carbide to permit formation of the direct carbide bonds between the carbide-forming alloy and the diamond cutting elements. 
     Although several embodiments of the invention have been disclosed in the foregoing specification, it is understood by those skilled in the art that many modifications and other embodiments of the invention will come to mind to which the invention pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. It is thus understood that the invention is not limited to the specific embodiments disclosed hereinabove, and that many modifications and other embodiments are intended to be comprised within the scope of the appended claims. Moreover, although specific terms are employed herein, as well as in the claims which follow, they are used only in a generic and descriptive sense, and not for the purposes of limiting the described invention, nor the claims which follow.