Superhard constructions and methods of making same

Abstract

A superhard polycrystalline construction comprises a body of polycrystalline superhard material having a first region and a second region adjacent to and bonded to the first region by intergrowth of grains of superhard material. The first region comprises a plurality of alternating strata or layers, each having a thickness in the range of around 5 to 300 microns. One or more strata or layers in the second region have a thickness greater than the thicknesses of the individual strata or layers in the first region. The alternating layers or strata in the first region comprise first layers or strata alternating with second layers or strata, the first layers or strata being in a state of residual compressive stress and the second layers or strata being in a state of residual tensile stress. One or more of the layers or strata in the first or second regions comprise a mass of superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, the superhard grains and a non-superhard phase at least partially filling a plurality of the interstitial regions. The median of the mean free path associated with the non-superhard phase divided by (Q 3− Q 1 ) for the non-superhard phase is greater than or equal to 0.50, where Q1 is the first quartile and Q3 is the third quartile; and the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains is less than 0.60.

1 . A superhard polycrystalline construction comprising a body of polycrystalline superhard material, the body of polycrystalline superhard material comprising a first region and a second region adjacent the first region, the second region being bonded to the first region by intergrowth of grains of superhard material; the first region comprising a plurality of alternating strata or layers, each stratum or layer having a thickness in the range of around 5 to 300 microns; the second region comprising a plurality of strata or layers, one or more strata or layers in the second region having a thickness greater than the thicknesses of the individual strata or layers in the first region, wherein:
 the alternating layers or strata in the first region comprise first layers or strata alternating with second layers or strata, the first layers or strata being in a state of residual compressive stress and the second layers or strata being in a state of residual tensile stress;   one or more of the layers or strata in the first or second regions comprises:   a mass of superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, the superhard grains having an associated mean free path; and   a non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path;   the median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase being greater than or equal to  0 . 50 , where Q1 is the first quartile and Q3 is the third quartile; and   the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains being less than 0.60.   
     
     
         2 . A superhard polycrystalline construction according to  claim 1 , wherein the superhard grains comprise natural and/or synthetic diamond grains, the superhard polycrystalline construction forming a polycrystalline diamond construction. 
     
     
         3 . A superhard polycrystalline construction according to  claim 1 , wherein the non-superhard phase comprises a binder phase. 
     
     
         4 . A superhard polycrystalline construction according to  claim 3 , wherein the binder phase comprises cobalt, and/or one or more other iron group elements, such as iron or nickel, or an alloy thereof, and/or one or more carbides, nitrides, borides, and oxides of the metals of Groups IV-VI in the periodic table. 
     
     
         5 . A superhard polycrystalline construction according to  claim 1 , further comprising a cemented carbide substrate bonded to the body of polycrystalline material along an interface. 
     
     
         6 . A superhard polycrystalline construction according to  claim 5 , wherein the cemented carbide substrate comprises tungsten carbide particles bonded together by a binder material, the binder material comprising an alloy of Co, Ni and Cr. 
     
     
         7 . A superhard polycrystalline construction according to  claim 6 , wherein the tungsten carbide particles form at least 70 weight percent and at most 95 weight percent of the substrate; the binder material comprising between about 10 to 50 wt. % Ni, between about 0.1 to 10 wt. % Cr, and the remainder weight percent comprising Co; and wherein the size distribution of the tungsten carbide particles in the cemented carbide substrate has the following characteristics:
 fewer than 17 percent of the tungsten carbide particles have a grain size of equal to or less than about 0.3 microns;   between about 20 to 28 percent of the tungsten carbide particles have a grain size of between about 0.3 to 0.5 microns;   between about 42 to 56 percent of the tungsten carbide particles have a grain size of between about 0.5 to 1 microns;   less than about 12 percent of the tungsten carbide particles are greater than 1 micron; and   the mean grain size of the tungsten carbide particles is about 0.6±0.2 microns.   
     
     
         8 . A superhard polycrystalline construction according to  claim 7 , wherein the binder additionally comprises between about 2 to 20 wt. % tungsten and between about 0.1 to 2 wt. % carbon. 
     
     
         9 . A superhard polycrystalline construction according to  claim 1 , wherein each stratum or layer in the first region has a thickness in the range of around 30 to 300 microns, or around 30 to 200 microns. 
     
     
         10 . A superhard polycrystalline construction according to  claim 1 , wherein the strata or layers in the second region have a thickness of greater than around 200 microns. 
     
     
         11 . A superhard polycrystalline construction according to  claim 1 , wherein the layers or strata in the first region comprise two or more different average diamond grain sizes. 
     
     
         12 . A superhard polycrystalline construction comprising a first region and a second region adjacent the first region, the second region being bonded to the first region by intergrowth of diamond grains; the first region comprising a plurality of alternating strata or layers, each layer or stratum in the first region having a thickness in the range of around 5 to 300 microns; one or more of the layers or strata in the first region and/or the second region comprises:
 a mass of superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, the superhard grains having an associated mean free path; and   a non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path;   the median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase being greater than or equal to 0.50, where Q1 is the first quartile and Q3 is the third quartile; and   the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains being less than 0.60.   
     
     
         13 . A superhard polycrystalline construction according to  claim 1 , wherein the first region comprises an external working surface forming the initial working surface of the superhard polycrystalline construction in use. 
     
     
         14 . A superhard polycrystalline construction according to  claim 12 , wherein the second region has a thickness greater than the thickness of the individual strata or layers in the first region. 
     
     
         15 . A superhard polycrystalline construction according to  claim 12 , wherein the second region comprises a plurality of layers or strata. 
     
     
         16 . A superhard polycrystalline construction according to  claim 12 , wherein the alternating layers or strata comprise first layers or strata alternating with second layers or strata, the first layers or strata being in a state of residual compressive stress and the second layers or strata being in a state of residual tensile stress. 
     
     
         17 . A superhard polycrystalline construction according to  claim 1 , wherein layers or strata in the first region and/or the second region comprise one or more of:
 up to 20 wt % nanodiamond additions in the form of nanodiamond powder grains;   salt systems;   borides or metal carbides of at least one of Ti, V, or Nb; or   at least one of the metals Pd or Ni.   
     
     
         18 . A superhard polycrystalline construction according to  claim 1 , wherein the superhard polycrystalline construction has a longitudinal axis, the layers or strata in the first region and/or the second region lying in a plane substantially perpendicular to the plane through which the longitudinal axis of the superhard polycrystalline construction extends. 
     
     
         19 . A superhard polycrystalline construction according to  claim 1 , wherein the layers or strata are substantially planar, curved, bowed or domed. 
     
     
         20 . A superhard polycrystalline construction according to  claim 1 , wherein the superhard polycrystalline construction has a longitudinal axis, the layers or strata in the first region and/or the second region lying in a plane at an angle to the plane through which the longitudinal axis of the PCD structure extends. 
     
     
         21 . A superhard polycrystalline construction according to  claim 1 , wherein the volume of the first region is greater than the volume of the second region. 
     
     
         22 . A superhard polycrystalline construction according to  claim 1 , wherein one or more of the strata or layers intersect a working surface or side surface of the superhard polycrystalline construction. 
     
     
         23 . A superhard polycrystalline construction according to  claim 1 , wherein each strata or layer is formed of one or more respective PCD grades having a TRS of at least 1,000 MPa; the PCD grade or grades in adjacent strata or layers having a different coefficient of thermal expansion (CTE). 
     
     
         24 . A superhard polycrystalline construction according to  claim 23 , wherein one or more of the strata or layers comprise a PCD grade or grades having a CTE of at least 3×10−6 mm/oC. 
     
     
         25 . A superhard polycrystalline construction as claimed in  claim 1 , wherein at least a portion of the first region is substantially free of a catalyst material for diamond, said portion forming a thermally stable region. 
     
     
         26 . A superhard polycrystalline construction as claimed in  claim 25 , wherein the thermally stable region extends a depth of at least 50 microns from a surface of the superhard polycrystalline construction. 
     
     
         27 . A superhard polycrystalline construction as claimed in  claim 25 , wherein the thermally stable region comprising at most 2 weight percent of catalyst material for diamond. 
     
     
         28 . A superhard polycrystalline construction for a rotary shear bit for boring into the earth, or for a percussion drill bit, comprising a superhard polycrystalline construction as claimed in  claim 1  bonded to a cemented carbide support body. 
     
     
         29 . A method of forming a superhard polycrystalline construction, comprising:
 providing a mass of grains of superhard material and arranging the mass of superhard grains to form a first region comprising a plurality of alternating strata or layers, each stratum or layer having a respective first fraction having a first average size and a second fraction having a second average size, and providing a further mass of grains of superhard material to form a second region adjacent the first region to form a pre-sinter assembly; and   treating the pre-sinter assembly in the presence of a catalyst/solvent material for the superhard grains at an ultra-high pressure of around 5.5 GPa or greater and a temperature at which the superhard material is more thermodynamically stable than graphite to sinter together the grains of superhard material to form a polycrystalline superhard construction, the superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, a non-superhard phase at least partially filling a plurality of the interstitial regions;   the second region being bonded to the first region by intergrowth of grains of superhard material; the first region a thickness in the range of around 5 to 300 microns; wherein:   the alternating layers or strata in the first region comprise first layers or strata alternating with second layers or strata, the first layers or strata being in a state of residual compressive stress and the second layers or strata being in a state of residual tensile stress;   the median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase is greater than or equal to 0.50, where Q1 is the first quartile and Q3 is the third quartile of the mean free path measurements associated with the non-superhard phase; and   the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains is less than 0.60, where Q1 is the first quartile and Q3 is the third quartile of the mean free path measurements associated with the superhard grains.   
     
     
         30 . The method of  claim 29 , wherein, the step of providing a mass of grains of superhard material comprises providing a mass of diamond grains having a first fraction having a first average size and a second fraction having a second average size, the first fraction having an average grain size ranging from about 10 to 60 microns, and the second fraction having an average grain size less than the size of the first fraction. 
     
     
         31 . The method of  claim 30 , wherein the second fraction has an average grain size between around 1/10 to 6/10 of the size of the first fraction. 
     
     
         32 . The method of  claim 29 , wherein the average grain size of the first fraction is between around 10 to 60 microns, and the average grain size of the second fraction is between about 0.1 to 20 microns. 
     
     
         33 . The method of  claim 29 , wherein the weight ratio of the first fraction to the second fraction ranges from about 50% to about 97%, the weight % of the second fraction ranging from about 3% to about 50 weight %. 
     
     
         34 . The method of  claim 33 , wherein the ratio by weight percent of the first fraction to the second fraction is around 60:40. 
     
     
         35 . The method of  claim 33 , wherein the ratio by weight percent of the first fraction to the second fraction is around 70:30. 
     
     
         36 . The method of  claim 33 , wherein the ratio by weight percent of the first fraction to the second fraction is around 90:10. 
     
     
         37 . The method of  claim 33 , wherein the ratio by weight percent of the first fraction to the second fraction is around 80:20. 
     
     
         38 . The method of  claim 29 , wherein the step of providing a mass of grains of superhard material comprises providing a mass of grains in which the grain size distributions of the first and second fractions do not overlap. 
     
     
         39 . The method of  claim 29 , wherein the step of providing a mass of grains of superhard material comprises providing three or more grain size modes to form a multimodal mass of grains comprising a blend of grain sizes having associated average grain sizes. 
     
     
         40 . The method of  claim 29 , wherein the average grain sizes of the fractions is separated by an order of magnitude. 
     
     
         41 . The method of  claim 39 , wherein the mass of superhard grains comprises a first fraction having an average grain size of around 20 microns, a second fraction having an average grain size of around 2 microns, a third fraction having an average grain size of around 200 nm and a fourth fraction having an average grain size of around 20 nm. 
     
     
         42 . A tool comprising a superhard polycrystalline construction according to  claim 1 , the tool being for cutting, milling, grinding, drilling, earth boring, rock drilling or other abrasive applications. 
     
     
         43 . A tool according to  claim 42 , wherein the tool comprises a drill bit for earth boring or rock drilling. 
     
     
         44 . A tool according to  claim 42 , wherein the tool comprises a rotary fixed-cutter bit for use in oil and gas drilling. 
     
     
         45 . A tool according to  claim 42 , wherein the tool is a rolling cone drill bit, a hole opening tool, an expandable tool, a reamer or other earth boring tools. 
     
     
         46 . A drill bit or a cutter or a component therefor comprising the superhard polycrystalline construction according to  claim 1 . 
     
     
         47 - 48 . (canceled)