Abstract:
A method for determining a position of a region within an ultra-hard polycrystalline body comprises directing x-rays onto the body, wherein the body includes one region that includes a target atom and another region that does not. The ultra-hard polycrystalline body can be in the form of a cutting element used with a subterranean drill bit. The x-rays penetrate the body and cause the target atom within the region including the same to emit x-ray fluorescence. The emitted x-ray fluorescence is received and the position of the second region within the body is determined therefrom. In one embodiment, the one region extends a depth from the surface, and the other region extends from one region into the body. The x-rays can be directed onto a number of different body surface portions to determine the placement position of the region comprising the target atom within the polycrystalline body.

Description:
RELATION TO COPENDING PATENT APPLICATIONS 
     This patent application claims priority of U.S. Provisional Patent Application Ser. No. 60/728,057, that was filed on Oct. 18, 2005, and which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to nondestructive methods developed for measuring the thickness or variation in thickness of a region within a material microstructure and, more specifically, to using X-ray fluorescence as a technique for measuring the thickness or variation in thickness of one or more region within an ultra-hard polycrystalline construction. 
     BACKGROUND OF THE INVENTION 
     The formation of constructions having a material microstructure made up or two or more different layers or regions of materials is well known. Such constructions are intentionally engineered in this fashion to provide a desired mix of physical, mechanical and/or thermal properties within the material microstructure, making it better equipped to handle a particular end use application. In order to provide such desired properties in a predictable and consistent manner, the thickness or variation of thickness of each engineered region must be controlled. 
     It is, therefore, necessary that the thickness of each such region within the construction be measured for the purpose of both controlling the process that is used to make the construction, and for controlling the quality or ability of the construction to perform as expected. Methods useful for measuring the thickness or variation in the thickness of a region within a material construction will vary depending on the nature of the construction. For material constructions used in tooling, wear, and cutting applications provided in the form of an ultra-hard polycrystalline material, e.g., comprising polycrystalline diamond, a useful method for measuring the thickness or variation of thickness of one or more region within the construction is by destructive method or destructive testing. 
     Destructive testing requires that the construction itself be cut or otherwise treated in a manner that physically exposes the different regions therein so that they can be measured by visual inspection. In an example embodiment, where the construction is one comprising an ultra-hard polycrystalline material such as diamond or cubic boron nitride, the construction itself is cut, e.g., in half, so that the different regions forming the construction can be viewed visually for purposes of measuring the thickness or variation of thickness of the regions. In an example embodiment, such visual indication is made with the assistance of a magnifying device such as a microscope, e.g., a scanning electron microscope. 
     While such destructive test method is useful for determining the thickness or variation of thickness within a construction, it is time consuming in that after the part is cut it must usually be further prepared by grinding, polishing or the like, then mounted for microscopic evaluation, and the microscopic evaluation must be taken over a number of different points to gather sufficient data to arrive at a numerical value, e.g., an average region thickness throughout the part. Further, the use of such destructive test method is expensive, and results in the parts that are measured being destroyed, thereby adversely impacting the economics of making the parts. 
     It is, therefore, desired that a method be developed that is capable of measuring the thickness or variation of thickness within a region of a material construction, e.g., an ultra-hard polycrystalline construction, in a manner that is not destructive. It is further desired that such a method be capable of providing such a desired measurement in a manner that has a consistent degree of accuracy. It is further desired that the method be capable of providing such a desired measurement for products where the region being measured may have a nonplanar or nonlinear configuration. 
     SUMMARY OF THE INVENTION 
     Methods of this invention are disclosed for determining a position of a region within an ultra-hard polycrystalline body. The ultra-hard polycrystalline body can be provided in the form of a cutting element, wherein the body is attached to a suitable substrate, and the cutting element is configured for attachment and use with a bit, e.g., for drilling subterranean earthen formations. The method comprises using a suitable device to direct x-rays onto at least a surface portion of the polycrystalline body. 
     The polycrystalline body comprises more than one region, and in an example embodiment, comprises a first region and a second region. In a preferred embodiment, the first and second regions each comprise bonded together diamond crystals. One of the regions includes a target atom that is selected so that it emits x-ray fluorescence in response to receiving x-ray radiation. In an example embodiment, the first region does not include the target atom, and the second region includes the target atom. The target atom can be a catalyst material used to form polycrystalline diamond, such as cobalt and the like. 
     When the x-rays are directed onto the body they reach the second region, and the target atoms in the second region emit x-ray fluorescence. The emitted x-ray fluorescence is received and the position of the second region within the body is determined therefrom. In an example embodiment, the first region extends a depth from the surface, and the second region extends from the first region a depth into the body. If desired, x-rays can directed onto a number of different surface portions of the body to determine the placement position, e.g., depth and/or thickness, of the region comprising the target atom within the polycrystalline body. 
     Methods of this invention are, therefore capable of measuring the placement position, thickness or variation of thickness within a region of a material construction, e.g., an ultra-hard polycrystalline construction, in a manner that is not destructive, and that has a consistent degree of accuracy. Further, methods this invention can be used to determine such placement position where the region being measured may have a nonplanar or nonlinear configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is schematic view of an ultra-hard polycrystalline construction provided in the form of a compact; 
         FIG. 2  is a cross-sectional side view of the ultra-hard polycrystalline construction taken along a section of  FIG. 1 ; 
         FIG. 3  is a schematic side view of an X-ray fluorescence device useful for determining the thickness and/or variations in thickness of a region within the ultra-hard polycrystalline construction of  FIGS. 1 and 2 ; 
         FIG. 4  is a measurement result taken from the X-ray fluorescence device of  FIG. 3 ; 
         FIG. 5  is a perspective side view of an insert, for use in a roller cone or a hammer drill bit, comprising the ultra-hard polycrystalline construction measured using X-ray fluorescence; 
         FIG. 6  is a perspective side view of a roller cone drill bit comprising a number of the inserts of  FIG. 5 ; 
         FIG. 7  is a perspective side view of a percussion or hammer bit comprising a number of inserts of  FIG. 5 ; 
         FIG. 8  is a schematic perspective side view of a diamond shear cutter comprising the ultra-hard polycrystalline construction measured using X-ray fluorescence; and 
         FIG. 9  is a perspective side view of a drag bit comprising a number of the shear cutters of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A nondestructive method useful for determining the thickness or variation of thickness within an ultra-hard polycrystalline construction, according to the principles of this invention, is X-ray fluorescence (XRF). As described in better detail below, XRF is used to determine the thickness and/or variation in thickness within a targeted region of the ultra-hard polycrystalline construction in a manner that is accurate and that does not result in the destruction of the part. 
       FIG. 1  illustrates an ultra-hard polycrystalline construction  10 . The construction comprises a body  12  formed from an ultra-hard polycrystalline material  14 , e.g., comprising diamond, polycrystalline diamond (PCD), cubic boron nitride (cBN), polycrystalline cubic boron nitride (PcBN), and mixtures thereof. The body  12  may or may not be attached to a substrate. In the example embodiment illustrated in  FIG. 1 , the construction is shown to include substrate  15  that is joined together with the body  12  to form a compact. 
     The substrate may be formed from a variety of different materials such as those useful for forming conventional PCD compacts, like ceramic materials, metallic materials, cermet materials, carbides, nitrides, and mixtures thereof. When the ultra-hard polycrystalline construction comprises polycrystalline diamond a preferred substrate material comprises cemented tungsten carbide (WC—Co). 
       FIG. 2  illustrates a cross-sectional view of a section taken through the ultra-hard polycrystalline construction  10  of  FIG. 1 , which illustrates the material microstructure of the construction and its different regions. In an example embodiment, the body  12  includes a first region  16 , that extends a depth “D” into the body from a outside body surface  18 , and a second region  20 , that extends from the first region  16  to the substrate  15 . An interface  22  within the body defines the point of transition between the first and second regions  16  and  20 . 
     In an example embodiment, the body  12  is formed from PCD and the first region  16  includes PCD that has been treated so that it is substantially free of a catalyst material used to form the PCD. As used herein, the term “substantially free” is understood to mean that the catalyst material is removed from the first region, in which case the first region has a material microstructure comprising a polycrystalline diamond matrix phase and a plurality of voids interposed therebetween. The term “substantially free” is also understood to include treatments that render the catalyst material used to form the PCD no longer catalytic, such as by reacting the catalyst material to form a noncatalytic compound and/or by encapsulating the catalyst material with another material that prevents the catalyst material from functioning as a catalyst with the polycrystalline diamond matrix phase. 
     The catalyst material used to form the PCD in the body can be the same as that used to form conventional PCD by high pressure/high temperature (HPHT) process, such as metals from Group VIII of the Periodic table, with cobalt (Co) being the most common. In an example embodiment, the catalyst material is a solvent metal catalyst such as Ni, Co, Fe, and combinations thereof. The catalyst material can be removed by chemical, electrical, or electrochemical processes. In an example embodiment, the catalyst material is Co and is removed by acid leaching process. 
     In an example embodiment, it is desired that the depth “D” of the first region within the body be controlled to provide consistent and repeatable characteristics of mechanical and thermal performance for the construction. As explained in greater detail below, it is therefore necessary to develop an accurate and repeatable technique for measuring the depth of the first region in the construction to ensure the consistency of such desired performance characteristics. 
     The body second region  20  comprises PCD that includes the catalyst material. The PCD region  20  has a material microstructure comprising a polycrystalline diamond matrix and the catalyst material disposed interstitially within the matrix. In an example embodiment, the substrate  15  is attached to the body  12  at the interface with the body second region  20 . 
     The depth of the first region can be controlled by adjusting one or more parameters of the process that are used to treat the first region to render it substantially free of the catalyst material. Once a desired depth is achieved, e.g., to meet the desired performance characteristics for a particular end use application, the process is carefully controlled so that the first region depth in all remaining parts are the same. As noted above, a current method that is used for measuring the depth of the body first region is by destructive testing, whereby the part is cut in half, polished or otherwise prepared, and then is viewed and measured using a scanning electron microscope. 
     While this technique enables one to determine the depth of the first region with some degree of accuracy, it also results in the destruction of the part, which adversely impacts manufacturing costs and efficiency. Additionally, this process is time consuming as the user typically measures the depth of the first region along the entire part diameter, and then takes the average of the measured points to arrive at the overall part average. 
     While the use of such destructive testing method is effective for determining the average depth of the first region  16  in the body of the part destroyed, the use of such method on a regular basis is not practical for a large scale manufacturing processes due to both the number of parts destroyed, and the time involved with preparing and measuring each such part. Ideally, it is desired that one be able to measure each and every part that is made for the purpose of ensuring its performance characteristics, rather than depending on a sampling method of testing only one of a number of manufactured parts, which sampling method ultimately relies on the consistency of the manufacturing process to ensure that the remaining unsampled parts conform with the sampled one. 
     Additionally, the use of such destructive testing technique also enables one to only view the region depth at one location within the part and is not useful in identifying any depth irregularities that may exist along the entire interface between the first and second regions, which depth irregularities (whether patterned or random) may impact the desired performance characteristics of the part. 
     XRF is a technique that can be used to nondestructively measure the depth of one or more identified regions in the body in a manner that is accurate, and in a manner that provides depth information across the entire region or surface area being measured. XRF relies on bombarding a target material with x-ray energy provided from an x-ray excitation source such as an e-ray tube or a radioactive source. Once the x-ray enters the material it is either absorbed by a target atom or scattered through the material. 
     When the x-ray is absorbed by a target atom, the atom transfers all of its energy to an innermost electron, which mechanism is referred to as the “photoelectric effect.” During this process, if the primary x-ray has sufficient energy, electrons are ejected from the inner shells of the atom, creating vacancies or voids in the vacated shells. These vacancies present an unstable condition for the atom. 
     Electrons from the atom&#39;s outer shells are transferred to the inner shells to return the atom to a stable condition. The process of electron transfer from the outer shell to the inner shell produces a characteristic x-ray having an energy that is the difference between the two binding energies of the corresponding shells. The x-rays emitted by the atom during this process are called X-ray fluorescence (XRF). The process of detecting and analyzing the emitted x-rays is called XRF analysis. Depending on the particular application, XRF can be produced by using not only x-rays but also other primary excitation sources like alpha particles, protons, or high-energy electron beams. 
     The energy level or wavelength of fluorescent x-rays emitted by the atom is proportional to the atomic number of the target atom and is characteristic for a particular material. The quantity of energy release via such emitted fluorescent x-rays is also dependent upon the thickness or depth of the material being measured. 
       FIG. 3  illustrates an XRF device  24  as used to measure the depth of one or more regions in the ultra-hard polycrystalline construction of  FIGS. 1 and 2 . In an example embodiment, the device  24  comprises an x-ray source  26  and can include a fail-safe shutter  28  and a collimator  30 . The collimator is used to direct an incident x-ray  32  onto a desired surface  34  of the ultra-hard polycrystalline construction  36  that is positioned on a suitable positioning assembly  38 . In an example embodiment, the positioning assembly and/or the x-ray source can be configured to move if necessary to provide extended coverage over a desired region of the ultra-hard polycrystalline construction  36 . 
     The device  24  further includes a proportional counter  40  that may be part of or separate from the device. The proportional counter may comprise a gas disposed within a counter tube, which gas is ionized by the emission of x-rays or photons from the target material. The emitted x-rays or photons ionize gas in the counter tube that is proportional to their energy, permitting spectrum analysis for determining the nature of the target material and its thickness. 
     In an example embodiment, the ultra-hard polycrystalline construction  36  is oriented with the device  24  so that the device emits x-ray energy onto the surface  34  of the ultra-hard polycrystalline construction from which the body first region extends. The device is configured having an x-ray source  26  selected to produce x-ray energy that will create a void in the inner shell of the catalyst material that is present in the body second region. In an example embodiment, the catalyst material is cobalt. In the event that the catalyst material in the second region is some other material, the x-ray source is selected to create a void in the inner shell of such other catalyst material. 
     In an example embodiment, the device is configured to emit x-rays onto a designated surface area of the ultra-hard polycrystalline construction to produce XRF from the targeted atoms, e.g., the catalyst material in the second region, within such designated surface area. X-rays that are generated by the device pass through the ultra-hard polycrystalline construction body first region and to the target atoms in the second region. The XRF emitted from the targeted atoms in the portion of the second region associated with the designated surface area is measured. In an example embodiment, the XRF emitted is an indication of the distance from the surface  34  of the ultra-hard polycrystalline construction to the second region, or the thickness or depth of the first region. 
     This measured data can be used to generate a plot of the first region thickness within the designated surface area. The device can be used multiple times to emit x-rays onto other surface areas of the ultra-hard polycrystalline construction to obtain desired measurement data and plot the first region thickness or depth a number of different surface areas. Generally speaking, the surface area of the target material that is covered by the device in one instance will vary depending on the size of the collimator. The larger the collimator the larger the surface area being covered, and the fewer number of times that the device will need to be used to generate measurement data sufficient to cover the entire surface area of the target material, if such is desired. 
     In an example embodiment, it may be desired to use the XRF device to obtain measurement data and plot the first region thickness or depth over the entire surface area of the ultra-hard polycrystalline construction. When used in this manner, the XRF device provides plotted measurement data that produces a topographical view of the interface between the first and second regions within the body. 
     Such a topographical view can be very helpful in identifying any irregularities along the entire interface, i.e., in the first region thickness or depth, that could possibly be the source of an undesired performance characteristic. Additionally, the use of such a topographical plot can help to identify whether any such irregularities are in a arranged in pattern or are random, which can be useful for the purpose of evaluating and/or controlling the process that is used to form the ultra-hard polycrystalline construction, e.g., to form the body first region. 
       FIG. 4  illustrates a plot  40  that is generated by using the XRF device of  FIG. 3 . The plot provides a topographical visual indication of the depth along a portion of the body first region (or the distance from the surface of the ultra-hard polycrystalline construction to the second region) within a predetermined surface area. In this example, the XRF device was used to generate a 400 point array scan of a surface area of the ultra-hard polycrystalline construction comprising a body having a polycrystalline diamond matrix first region substantially free of a catalyst material, and a PCD second region that includes a cobalt catalyst material, wherein the target atom is cobalt. The designated surface area had a size of approximately 0.1 by 0.025 inches. 
     As illustrated in the plot  40 , different depths along portion of the first region within this surface area are indicated by differently colored regions  44 ,  46 ,  48 ,  50 ,  52 ,  54 ,  56  and  58 . In an example embodiment, a legend  60  is provided to match the colors of the plot to a corresponding numerical thickness. In the example embodiment that is illustrated, the numerical data provided in the legend is provided in dimensions of micrometers. 
     XRF can be used to nondestructively measure the depth of one or more regions of ultra-hard polycrystalline constructions that are configured for use in a number of different applications, such as tools for mining, cutting, machining and construction applications. Such ultra-hard polycrystalline constructions are particularly well suited for forming working, wear and/or cutting components in machine tools and drill and mining bits such as roller cone rock bits, percussion or hammer bits, diamond bits, and shear cutters. 
       FIG. 5  illustrates an embodiment of an ultra-hard polycrystalline construction, comprising one or more regions within the body that can be measured using XRF, provided in the form of an insert  62  used in a wear or cutting application in a roller cone drill bit or percussion or hammer drill bit. For example, such inserts  62  are constructed having a substrate portion  64 , formed from one or more of the substrate materials disclosed above, that is attached to a body  66  having a first and second region as described above. In this particular embodiment, the insert comprises a domed working surface  68 , and the thermally stable region is positioned along the working surface and extends a selected depth therefrom into the diamond body. The insert can be pressed or machined into the desired shape or configuration prior to the treatment for rendering the selected region thermally stable. It is to be understood that ultra-hard polycrystalline constructions can be configured as inserts having geometries other than that specifically described above and illustrated in  FIG. 5 . 
       FIG. 6  illustrates a rotary or roller cone drill bit in the form of a rock bit  70  comprising a number of the wear or cutting inserts  72  disclosed above and illustrated in  FIG. 5 . The rock bit  70  comprises a body  74  having three legs  76  extending therefrom, and a roller cutter cone  78  mounted on a lower end of each leg. The inserts  72  are the same as those described above comprising the ultra-hard material construction, and are provided in the surfaces of each cutter cone  78  for bearing on a rock formation being drilled. 
       FIG. 7  illustrates the insert described above and illustrated in  FIG. 5  as used with a percussion or hammer bit  80 . The hammer bit generally comprises a hollow steel body  82  having a threaded pin  84  on an end of the body for assembling the bit onto a drill string (not shown) for drilling oil wells and the like. A plurality of the inserts  86  are provided in the surface of a head  88  of the body  82  for bearing on the subterranean formation being drilled. 
       FIG. 8  illustrates an ultra-hard polycrystalline construction measured using the XRF method described above as embodied in the form of a shear cutter  90  used, for example, with a drag bit for drilling subterranean formations. The shear cutter  90  comprises a polycrystalline body  92  that is sintered or otherwise attached to a substrate  94 . The body  92  includes a working or cutting surface  96  that is formed from the body first region. The working or cutting surface of the shear cutter can extend from the upper surface to a beveled surface (shown as  13  in  FIG. 1 ) defining a circumferential edge of the upper, and the first region of the body can extend a depth from such working surfaces. It is to be understood that ultra-hard polycrystalline constructions can be configured as shear cutters having geometries other than that specifically described above and illustrated in  FIG. 8 . 
       FIG. 9  illustrates a drag bit  98  comprising a plurality of the shear cutters  100  described above and illustrated in  FIG. 8 . The shear cutters are each attached to blades  102  that extend from a head  104  of the drag bit for cutting against the subterranean formation being drilled. Because the shear cutters of this invention include a metallic substrate, they are attached to the blades by conventional method, such as by brazing or welding. 
     Other modifications and variations of using XRF techniques and methods to measure the thickness or depth of one or more regions within an ultra-hard polycrystalline constructions will be apparent to those skilled in the art. It is, therefore, to be understood that within the scope of the appended claims, this invention may be practiced otherwise than as specifically described.