Superhard constructions & methods of making same

Abstract

A super hard polycrystalline construction is disclosed as comprising a body of super hard material having a first fraction of super hard grains in a matrix of a second fraction of super hard grains. The average grain size of the first fraction is between around 1.5 to around 10 times the average grain size of the second fraction and the first fraction comprises around 5 vol % to around 30 vol % of the grains of super hard material in the body.

1 . A super hard polycrystalline construction comprising:
 a body of super hard material having a first fraction of super hard grains in a matrix of a second fraction of super hard grains; wherein:   the average grain size of the first fraction is between around 1.5 to around 10 times the average grain size of the second fraction; and   the first fraction comprises around 5 vol % to around 30 vol % of the grains of super hard material in the body.   
     
     
         2 . The construction of  claim 1 , wherein the average grain size of the first fraction is between around 2 to around 7 times the average grain size of the second fraction. 
     
     
         3 . The construction of  claim 1 , wherein the first fraction of super hard grains comprises any one or more of single crystal particles or polycrystalline agglomerates of diamond grit, CVD crushed particles, diamond obtained by PVD methods, natural diamond, diamond of synthetic origin, or cBN. 
     
     
         4 . The construction of  claim 1 , wherein the second fraction of super hard grains comprises diamond grains and/or cBN gains. 
     
     
         5 . The construction of  claim 1 , wherein the second fraction of super hard grains comprises a plurality of intergrown grains of super hard material. 
     
     
         6 . The construction of  claim 1 , wherein the body has at least one region substantially free of a catalyst material for diamond, said region forming a thermally stable region. 
     
     
         7 . The construction of  claim 6 , wherein the body comprises at most 3 weight percent of catalyst material for diamond. 
     
     
         8 . The construction of  claim 1 , further comprising a substrate bonded to the body of super hard material along an interface. 
     
     
         9 . The construction of  claim 8  wherein the substrate comprises a cemented carbide material. 
     
     
         10 . (canceled) 
     
     
         11 . The construction of  claim 1  wherein the body further comprises a region having a different composition to the first and second fractions. 
     
     
         12 . The construction of  claim 11 , wherein the region comprises interbonded super hard material having a different average super hard grain size or elemental composition to the first and/or second fractions. 
     
     
         13 . A super hard polycrystalline construction for a rotary shear bit for boring into the earth, or for a percussion drill bit, comprising the super hard polycrystalline construction as claimed in  claim 1 . 
     
     
         14 . A tool comprising a super hard polycrystalline construction according to  claim 1 , the tool being for cutting, milling, grinding, drilling, earth boring, rock drilling or another abrasive application. 
     
     
         15 . A tool according to  claim 14 , wherein the tool comprises a drill bit for earth boring or rock drilling. 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . A drill bit or a cutter or a component therefor comprising the super hard polycrystalline construction according to  claim 1 . 
     
     
         19 . A method of forming a super hard polycrystalline construction comprising:
 forming a pre-sinter assembly comprising:   a first mass of grains or particles of a super hard material;   a second mass of grains or particles of a super hard material; the first mass of super hard grains in having an average grain size between around 1.5 to around 10 times the average grain size of the grains in the second mass; and   a substrate; the method further comprising the steps of:   treating the pre-sinter assembly at an ultra-high pressure of around 5 GPa or greater and a temperature to bond together the grains of super hard material to form a body of interbonded polycrystalline super hard material bonded to the substrate, the first mass forming a first fraction comprising around 5 vol % to around 30 vol % of the grains of super hard material in the body.   
     
     
         20 . The method of  claim 19 , further comprising treating the polycrystalline super hard construction to remove accessible residual catalyst/binder material from at least some interstitial spaces between the interbonded grains of super hard material. 
     
     
         21 . The method of  claim 19 , wherein
 the step of forming the pre-sinter assembly comprises:   providing a mass of diamond grains or particles and/or cubic boron nitride grains or particles to form the first mass of grains or particles of super hard material.   
     
     
         22 . The method of  claim 19 , wherein the step of forming the pre-sinter assembly comprises:
 providing a source of cobalt as the catalysing material for the super hard grains.