Superhard constructions and methods of making same

Abstract

A superhard polycrystalline construction comprises a body of polycrystalline superhard material formed of 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 average grain size of the superhard grains is less than or equal to 25 microns; and the ratio of the standard deviation in the mean free path associated with the non-superhard phase to the mean of the mean free path associated with the non-superhard phase is greater than or equal to 80% when measured using image analysis techniques at a magnification of 1000. There is also disclosed a method of forming such a superhard polycrystalline construction.

1 . A superhard polycrystalline construction comprising a body of polycrystalline superhard material formed of:
 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;   a non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path;   wherein:
 the average grain size of the superhard grains is less than or equal to 25 microns; and 
 the ratio of the standard deviation in the mean free path associated with the non-superhard phase to the mean of the mean free path associated with the non-superhard phase is greater than or equal to 80% when measured using image analysis techniques at a magnification of 1000. 
   
     
     
         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 . (canceled) 
     
     
         4 . A superhard polycrystalline construction according to  claim 1 , wherein the non-superhard phase comprises a binder phase, the binder phase comprising 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 .- 8 . (canceled) 
     
     
         9 . A superhard polycrystalline construction according to  claim 1 , wherein the average grain size of the superhard grains is between around 8 to 20 microns. 
     
     
         10 . A superhard polycrystalline construction according to  claim 1  wherein the ratio of the standard deviation in the mean free path associated with the non-superhard phase to the mean of the mean free path associated with the non-superhard phase is less than 150% when measured using image analysis techniques at a magnification of 1000. 
     
     
         11 . A superhard polycrystalline construction according to  claim 1  wherein the ratio of the standard deviation in the mean free path associated with the non-superhard phase to the mean of the mean free path associated with the non-superhard phase is less than 120% when measured using image analysis techniques at a magnification of 1000. 
     
     
         12 . A superhard polycrystalline construction according to  claim 1 , wherein the body of polycrystalline superhard material comprises 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; and   one or more of the layers or strata in the first or second regions comprises:
 the mass of superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween; and 
 the non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path; the ratio of the standard deviation in the mean free path associated with the non-superhard phase to the mean of the mean free path associated with the non-superhard phase is greater than or equal to 80% when measured using image analysis techniques at a magnification of 1000. 
   
     
     
         13 . A superhard polycrystalline construction according to  claim 12 , 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. 
     
     
         14 . A superhard polycrystalline construction according to  claim 12 , wherein the strata or layers in the second region have a thickness of greater than around 200 microns. 
     
     
         15 . A superhard polycrystalline construction according to  claim 12 , wherein the layers or strata in the first region comprise two or more different average diamond grain sizes. 
     
     
         16 . A superhard polycrystalline construction according to  claim 1 , wherein the body of polycrystalline superhard material comprises 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; and   a non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path; wherein:   the ratio of the standard deviation in the mean free path associated with the non-superhard phase to the mean of the mean free path associated with the non-superhard phase being greater than or equal to 80% when measured using image analysis techniques at a magnification of 1000.   
     
     
         17 .- 19 . (canceled) 
     
     
         20 . A superhard polycrystalline construction according to  claim 16 , 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. 
     
     
         21 . A superhard polycrystalline construction according to  claim 12 , 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.   
     
     
         22 . A superhard polycrystalline construction according to  claim 12 , wherein the PCD structure 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 PCD structure extends. 
     
     
         23 . A superhard polycrystalline construction according to  claim 12 , wherein the layers or strata are substantially planar, curved, bowed or domed. 
     
     
         24 . A superhard polycrystalline construction according to  claim 12 , wherein the PCD structure 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. 
     
     
         25 . A superhard polycrystalline construction according to  claim 12 , wherein the volume of the first region is greater than the volume of the second region. 
     
     
         26 . A superhard polycrystalline construction according to  claim 12 , wherein one or more of the strata or layers intersect a working surface or side surface of the PCD structure. 
     
     
         27 . A superhard polycrystalline construction according to  claim 12 , 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). 
     
     
         28 . (canceled) 
     
     
         29 . A superhard polycrystalline construction as claimed in  claim 12 , 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. 
     
     
         30 .- 31 . (canceled) 
     
     
         32 . A superhard construction according to  claim 1  further comprising:
 a substrate comprising a periphery and an interface surface and a longitudinal axis; wherein the body of polycrystalline superhard material is formed over the substrate and having an exposed outer surface, a peripheral surface extending therefrom and an interface surface; 
 wherein one of the interface surface of the substrate or the interface surface of the body of polycrystalline superhard material comprises: 
 a plurality of spaced-apart projections arranged to project from the interface surface, the interface surface between the spaced-apart projections being uneven. 
 
     
     
         33 .- 50 . (canceled) 
     
     
         51 . The superhard construction of  claim 32 , wherein the superhard construction is a cutter element. 
     
     
         52 - 74 . (canceled)