Superhard constructions and methods of making same

Abstract

A superhard polycrystalline construction comprises a body of polycrystal-line 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 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 0.83 where Q 1 is the first quartile and Q 3 is the third quartile and the median of the mean free path associated with the superhard grains divided by (Q 3 -Q 1 ) for the superhard grains is less than 0.47.

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 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 0.83, where Q 1  is the first quartile and Q 3  is the third quartile; and   the median of the mean free path associated with the superhard grains divided by (Q 3 -Q 1 ) for the superhard grains is less than 0.47.   
     
     
         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, 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 4 , wherein the one or more other iron group elements comprises iron or nickel. 
     
     
         6 . A superhard polycrystalline construction according to  claim 1 , further comprising a cemented carbide substrate bonded to the body of polycrystalline material along an interface. 
     
     
         7 . A superhard polycrystalline construction according to  claim 6 , 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. 
     
     
         8 . A superhard polycrystalline construction according to  claim 7 , 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.   
     
     
         9 . A superhard polycrystalline construction according to  claim 8 , wherein the binder additionally comprises between about 2 to 20 wt. % tungsten and between about 0.1 to 2 wt. % carbon. 
     
     
         10 . A method of forming a superhard polycrystalline construction, comprising:
 providing a mass of grains of superhard material comprising a first fraction having a first average size and a second fraction having a second average size, arranging the mass of superhard grains 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;   wherein 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 0.83, where Q 1  is the first quartile and Q 3  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 (Q 3 -Q 1 ) for the superhard grains is less than 0.47, where Q 1  is the first quartile and Q 3  is the third quartile of the mean free path measurements associated with the superhard grains.   
     
     
         11 . The method of  claim 10 , wherein, the step of providing a mass of grains of superhard material comprisies 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. 
     
     
         12 . The method of  claim 11 , wherein the second fraction has an average grain size between around 1/10 to 6/10 of the size of the first fraction. 
     
     
         13 . The method of  claim 10 , 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. 
     
     
         14 . The method of  claim 10 , wherein the weight ratio of the first fraction to the second fraction ranges from about 50% to about 97%, or the weight % of the second fraction ranging from about 3% to about 50 weight %. 
     
     
         15 . The method of  claim 14 , wherein the ratio by weight percent of the first fraction to the second fraction is around 60:40. 
     
     
         16 . The method of  claim 15 , wherein the ratio by weight percent of the first fraction to the second fraction is around 70:30. 
     
     
         17 . The method of  claim 16 , wherein the ratio by weight percent of the first fraction to the second fraction is around 90:10. 
     
     
         18 . The method of  claim 17 , wherein the ratio by weight percent of the first fraction to the second fraction is around 80:20. 
     
     
         19 . The method of  claim 10 , 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. 
     
     
         20 . The method of  claim 10 , 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. 
     
     
         21 . The method of  claim 10 , wherein the average grain sizes of the fractions is separated by an order of magnitude. 
     
     
         22 . The method of  claim 10 , 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. 
     
     
         23 . 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. 
     
     
         24 . A tool according to  claim 23 , wherein the tool comprises a drill bit for earth boring or rock drilling. 
     
     
         25 . A tool according to  claim 23 , wherein the tool comprises a rotary fixed-cutter bit for use in oil and gas drilling. 
     
     
         26 . A tool according to  claim 23 , wherein the tool is a rolling cone drill bit, a hole opening tool, an expandable tool, a reamer or other earth boring tools. 
     
     
         27 . A drill bit or a cutter or a component therefor comprising the superhard polycrystalline construction according to  claim 1 . 
     
     
         28 - 29 . (canceled)