Superhard constructions & methods of making same

Abstract

A superhard polycrystalline construction comprises a body of polycrystalline superhard material comprising a first superhard phase having a first average grain size; and a second superhard phase having a second average grain size. The second superhard phase is located in one or more channels or apertures in the first superhard phase, the first superhard phase forming a skeleton in the body of superhard material. The second superhard phase is bonded to the first superhard phase by a non-superhard phase and the first superhard phase differs from the second superhard phase in average grain size and/or composition. There is also disclosed a method of making such a superhard polycrystalline construction.

1 . A superhard polycrystalline construction comprising:
 a body of polycrystalline superhard material, the body of polycrystalline superhard material comprising:   a first superhard phase having a first average grain size; and   a second superhard phase having a second average grain size;   wherein the second superhard phase is located in one or more channels or apertures in the first superhard phase, the first superhard phase forming a skeleton in the body of superhard material, the second superhard phase being bonded to the first superhard phase by a non-superhard phase;   and wherein the first superhard phase differs from the second superhard phase in average grain size and/or composition.   
     
     
         2 . A superhard polycrystalline construction according to  claim 1 , wherein the superhard grains of the first and the second superhard phases comprise natural and/or synthetic diamond grains, the superhard polycrystalline construction forming a polycrystalline diamond construction. 
     
     
         3 . A superhard polycrystalline construction according to any one of the preceding claims, 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 any one of the preceding claims, 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 any one of  claim 5  or  6 , wherein the cemented carbide substrate comprises between around 8 to 13 weight or volume % binder material. 
     
     
         8 . A superhard polycrystalline construction according to any one of the preceding claims, wherein at least a portion of the body of superhard material is substantially free of a catalyst material for diamond, said portion forming a thermally stable region. 
     
     
         9 . A superhard polycrystalline construction as claimed in  claim 8 , wherein the thermally stable region comprises at most 2 weight percent of catalyst material for diamond. 
     
     
         10 . A superhard polycrystalline construction according to any one of the preceding claims, wherein the skeleton formed of the first superhard phase comprises a perforated disc having said plurality of channels and/or apertures therein, the disc comprising a mass of interbonded superhard grains, the second superhard phase filling the channels and/or apertures in the disc. 
     
     
         11 . A superhard polycrystalline construction according to  claim 10 , wherein the skeleton formed of the first superhard phase comprises a plurality of stacked perforated discs. 
     
     
         12 . A superhard polycrystalline construction according to  claim 11 , wherein the discs are aligned such that the second superhard phase filling the channels and/or apertures form one or more of alternating sectors, concentric layers or regions, or layers or regions inclined with respect to the central longitudinal axis of the discs. 
     
     
         13 . A superhard polycrystalline construction according to any one of the preceding claims wherein the skeleton is pre-formed and has been subjected to two or more sintering processes. 
     
     
         14 . A superhard polycrystalline construction according to any one of the preceding claims wherein the skeleton comprises two or more channels and/or apertures therein, the body of polycrystalline superhard material comprising a working surface, the working surface being formed of alternating portions of the skeleton and the second superhard phase located in the two or more channels and/or apertures in the skeleton. 
     
     
         15 . 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 any one of the preceding claims bonded to a cemented carbide support body. 
     
     
         16 . A method of forming a superhard polycrystalline construction, comprising:
 providing a first mass of particles or grains of superhard material for forming a first superhard phase; sintering the first superhard phase and forming a skeleton having a plurality of channels and/or apertures therein;   providing a second mass of superhard grains or particles for forming a second superhard phase;   positioning the second mass of superhard grains or particles in one or more channels and/or apertures in the skeleton formed of the first superhard phase to form a pre-sinter assembly; wherein the first superhard phase differs from the second superhard phase in average grain size and/or composition; 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, wherein the body of polycrystalline superhard material comprises a working surface, the working surface being formed of alternating portions of the skeleton and the second superhard phase located in the plurality of channels and/or apertures in the skeleton.   
     
     
         17 . A method according to  claim 16 , wherein the step of providing a first mass of grains of superhard material and a second mass of superhard material comprises providing a first and second mass of diamond grains. 
     
     
         18 . A method according to  claim 17 , wherein the step of providing a first mass and a second mass of diamond grains comprises providing a first and/or a second mass of 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 coarse fraction. 
     
     
         19 . The method of  claim 18 , wherein the second fraction has an average grain size between around 1/10 to 6/10 of the size of the first fraction. 
     
     
         20 . The method of any one of  claim 18  or  19 , 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. 
     
     
         21 . The method of any one of  claims 18  to  20 , wherein the weight ratio of the first fraction to the second fraction ranges from about 50% to about 97%, the weight ratio of the second fraction ranging from about 3% to about 50 weight %. 
     
     
         22 . The method of  claim 18 , wherein the ratio by weight percent of the first fraction to the second fraction is around 60:40. 
     
     
         23 . The method of  claim 18 , wherein the ratio by weight percent of the first fraction to the second fraction is around 70:30. 
     
     
         24 . The method of  claim 18 , wherein the ratio by weight percent of the first fraction to the second fraction is around 90:10. 
     
     
         25 . The method of  claim 18 , wherein the ratio by weight percent of the first fraction to the second fraction is around 80:20. 
     
     
         26 . The method of any one of  claims 18  to  25 , 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. 
     
     
         27 . The method of any one of  claims 18  to  26 , 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. 
     
     
         28 . The method of  claim 18 , wherein the average grain sizes of the fractions is separated by an order of magnitude. 
     
     
         29 . The method of any one of  claims 16  to  28 , wherein the step of providing the first mass of superhard grains comprises sintering a first body of superhard grains; and forming the channels and/or apertures therein after sintering and prior to the step of positioning the second mass of superhard grains or particles in said channels and/or apertures. 
     
     
         30 . The method of  claim 29 , wherein the step of forming the channels and/or apertures comprises forming said apertures and/or channels using an EDM technique, or a laser ablation technique. 
     
     
         31 . The method of any one of  claim 29  or  30 , further comprising treating at least a portion of the sintered first mass of superhard grains to render said portion free of a catalyst material for the superhard grains, said portion forming a thermally stable region. 
     
     
         32 . The method of any one of  claims 16  to  28 , wherein the step of providing the first mass of superhard grains comprises forming a green body comprising the first mass of superhard particles or grains with said channels and/or apertures therein using one or more of 3D printing or injection molding techniques. 
     
     
         33 . The method of any one of  claims 16  to  32 , wherein the step of providing a first mass of superhard grains comprises providing a perforated disc forming the first mass having said a plurality of apertures and/or channels therein, the disc comprising a mass of interbonded superhard grains, the second superhard phase filling the apertures and/or channels in the disc. 
     
     
         34 . The method of  claim 33 , wherein the first superhard construction comprises a plurality of stacked perforated discs. 
     
     
         35 . The method of  claim 34 , further comprising aligning the discs such that the second superhard phase filling the apertures and/or channels forms one or more of alternating sectors, concentric layers or regions, or layers or regions inclined with respect to the central longitudinal axis of said discs, the step of sintering comprising bonding the discs together by infiltration and reaction with the non-superhard phase. 
     
     
         36 . A method according to any one of  claims 16  to  35 , further comprising providing a cemented carbide substrate for bonding to the body of polycrystalline material along an interface during the step of sintering. 
     
     
         37 . A tool comprising a superhard polycrystalline construction according to any one of  claims 1  to  15 , the tool being for cutting, milling, grinding, drilling, earth boring, rock drilling or other abrasive applications. 
     
     
         38 . A tool according to  claim 37 , wherein the tool comprises a drill bit for earth boring or rock drilling. 
     
     
         39 . A tool according to  claim 7  wherein the tool comprises a rotary fixed-cutter bit for use in the oil and gas drilling industry. 
     
     
         40 . A tool according to  claim 37 , wherein the tool is a rolling cone drill bit, a hole opening tool, an expandable tool, a reamer or other earth boring tools. 
     
     
         41 . A drill bit or a cutter or a component therefor comprising the superhard polycrystalline construction according to any one of  claims 1  to  15 . 
     
     
         42 . A superhard polycrystalline construction substantially as hereinbefore described with reference to any one embodiment as that embodiment is illustrated in the accompanying drawings. 
     
     
         43 . A method of making a superhard polycrystalline construction, substantially as hereinbefore described with reference to any one embodiment as that embodiment is illustrated in the accompanying drawings.