Superhard constructions & methods of making same

Abstract

A polycrystalline super hard construction comprises a body of polycrystalline super hard material and a substrate bonded to the body along an interface. The substrate a first end surface forming the interface, the first end surface comprising a projection extending from the body of the substrate into the body of super hard material towards the cutting face, the body of polycrystalline material extending around the projection. The body of polycrystalline material comprises a first region more thermally stable than a second region, the first region comprising an annular portion located around the projection, the second region extending between and bonding the first region to the substrate. The first region has a thickness from the cutting face along the peripheral side edge to the interface of at least around 3 mm and a portion of the projection has a thickness measured in a plane extending along the longitudinal axis of at least around 3 mm.

1 . A polycrystalline superhard construction comprising:
 a body of polycrystalline superhard material having a cutting face and a cutting edge; and   a substrate bonded to the body of polycrystalline superhard material along an interface;   the construction having a central longitudinal axis extending therethrough and a peripheral side edge; wherein:   the substrate comprises a substrate body and a first end surface forming the interface, the first end surface of the substrate comprising a projection extending from the body of the substrate into the body of superhard material towards the cutting face, the body of polycrystalline material extending around the projection;   wherein the body of polycrystalline material comprises a first region and a second region, the first region being more thermally stable than the second region, the first region comprising an annular portion located around the projection extending from the body of the substrate, the cutting edge being in the first region, the second region extending between and bonding the first region to the substrate at one or more locations; and   wherein the first region body of polycrystalline material has a thickness from the cutting face along the peripheral side edge to the interface with the substrate of at least around 3 mm; and   wherein at least a portion of the projection has a thickness measured in a plane extending along the longitudinal axis of the construction of at least around 3 mm.   
     
     
         2 . The polycrystalline superhard construction of  claim 1 , wherein the projection from the substrate extends to and forms part of the working face. 
     
     
         3 . The polycrystalline superhard construction of  claim 1  wherein the first region body of polycrystalline material has a thickness from the cutting face along the peripheral side edge to the interface with the substrate of at least around 4 mm; and at least a portion of the projection has a thickness measured in a plane extending along the longitudinal axis of the construction of at least around 4 mm. 
     
     
         4 . The polycrystalline superhard construction of  claim 1 , wherein the first region differs from the second region in one or more characteristics comprising one or more of average grain size of superhard material, coefficient of thermal expansion, super hard material grain size distribution, hardness, impact resistance, and super hard material composition. 
     
     
         5 . (canceled) 
     
     
         6 . The polycrystalline superhard construction of  claim 1 , wherein the second region has a larger average grain size of superhard grains than the first region. 
     
     
         7 . (canceled) 
     
     
         8 . The polycrystalline superhard construction of  claim 1 , wherein the body of superhard material comprises polycrystalline diamond material having interbonded diamond grains and interstices therebetween; and wherein at least a portion of the body of superhard material forming the first region is substantially free of a catalyst material for diamond. 
     
     
         9 . The polycrystalline superhard construction of  claim 1 , wherein the body of superhard material comprises polycrystalline diamond material having interbonded diamond grains and interstices therebetween; and wherein at least 50 vol % of the body of superhard material forming the first region is substantially free of a catalyst material for diamond. 
     
     
         10 . The polycrystalline superhard construction of  claim 1 , wherein the projection from the substrate extends to a distance of around 0.5 mm or less from the cutting face. 
     
     
         11 - 15 . (canceled) 
     
     
         16 . The polycrystalline superhard construction of  claim 1 , further comprising a protective layer over at least a portion of the cutting face. 
     
     
         17 . The polycrystalline superhard construction of  claim 16 , wherein the protective layer comprises any one or more of a polymer, an oxide, paint, or a composite material to protect the cutting face or a portion thereof from one or more of erosion, corrosion or chemical degradation. 
     
     
         18 . The polycrystalline superhard construction of  claim 1 , wherein the second region comprises one or more of a mixture of WC and diamond powder(s), a mixture of cBN and diamond powder(s), and/or a mixture of refractory metal(s) and hard material powders, the hard material powders comprising one or more of tungsten, vanadium or molybdenum. 
     
     
         19 . The polycrystalline superhard construction of  claim 1 , wherein the projection is dome shaped. 
     
     
         20 . The polycrystalline superhard construction of  claim 1 , wherein the projection comprises a planar central portion spaced from the body of the substrate by an interconnecting surface. 
     
     
         21 . The polycrystalline superhard construction of  claim 20 , wherein the planar central portion has a circular cross-section. 
     
     
         22 . The polycrystalline superhard construction of  claim 20 , wherein the interconnecting surface is concave. 
     
     
         23 . The polycrystalline superhard construction of  claim 22 , wherein the interconnecting surface extends from the planar central section to the peripheral side edge of the construction. 
     
     
         24 . The polycrystalline superhard construction of  claim 23 , wherein the projection is frusto-conical in shape. 
     
     
         25 . The polycrystalline superhard construction of  claim 20 , wherein the interconnecting surface comprises a first portion extending from the planar central section to a position spaced from the peripheral side edge of the construction, the interconnecting surface further comprising a second portion extending form the first portion to the peripheral side edge, the projection being substantially frusto-conical in shape. 
     
     
         26 . The polycrystalline superhard construction of  claim 25 , wherein the second portion forms a shoulder portion having a length of up to around 3 mm. 
     
     
         27 . The polycrystalline superhard construction of  claim 25 , wherein the projection has a peripheral outer surface inclined at an angle of up to around 30 degrees from the central longitudinal axis. 
     
     
         28 - 29 . (canceled) 
     
     
         30 . A method of forming a superhard polycrystalline construction, comprising:
 providing a first mass of particles or grains of superhard material;   admixing the first mass of particles or grains with a binder material to form a first green body;   placing the first green body into a canister to form a first pre-sinter assembly;   treating the first 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 to sinter together the grains of superhard material to form a first polycrystalline superhard construction;   processing the first polycrystalline superhard construction to form a first thermally stable annular region;   preparing a second pre-sinter assembly comprising placing a second mass of particles or grains of superhard material to form a second polycrystalline superhard region in contact with a pre-formed substrate and the first thermally stable annular region, the pre-formed substrate having a longitudinal axis and comprising a body portion and a projection, the projection extending at least in part from the body portion by around 3 mm or greater as measured in a plane parallel to the longitudinal axis of the substrate;   
       treating the second 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 to sinter together the second: mass of grains of superhard material to form the second region and bond the substrate to the first and second regions of polycrystalline superhard material; wherein the projection extends from the body of the substrate into the body of superhard material towards a cutting face, the body of polycrystalline material extending around the projection; end wherein the body of polycrystalline material has a thickness from the cutting face along a peripheral side edge of the construction to the interface with the substrate of at least around 3 mm, the cutting face being in the first region. 
     
     
         31 - 33 . (canceled) 
     
     
         34 . The method of  claim 30 , wherein the step of placing the first green body into a canister to form a first pre-sinter assembly further comprises pressing the superhard particles or grains around a pre-sintered shaped substrate, coated with a layer prevent bonding between the superhard particles and the substrate during the first sintering stage, the substrate being shaped to impart the annular shape to the superhard particles of grains once entered; and
 wherein the step of processing the first polycrystalline superhard construction to form a first annular region comprises removing the shaped substrate after sintering.   
     
     
         35 . The method of  claim 34 , wherein the shaped substrate is coated with one or more of zirconia or alumina. 
     
     
         36 - 45 . (canceled) 
     
     
         46 . The method of  claim 30 , wherein the first polycrystalline super hard construction comprises a first substrate having a substrate body and a projection extending from the body of the first substrate into the body of super hard material, the body of polycrystalline material extending around the projection and being bonded to the first substrate along an interface; and wherein the body of polycrystalline material has a thickness from the cutting face along a peripheral side edge of the construction to the Interface with the first substrate of at least around 3 mm; and
 wherein the step of processing the first polycrystalline super hard construction to from the first thermally stable annular region comprises:   removing at least a part of the first substrate from the first polycrystalline construction;   treating the first polycrystalline construction to remove residual catalyst/binder from the majority of interstitial spaces In the first polycrystalline construction and the residual first substrate.   
     
     
         47 - 55 . (canceled)