Polycrystalline superhard construction

Abstract

A polycrystalline superhard construction comprises a body of polycrystalline superhard material, and a substrate of hard material bonded thereto along an interface. The body of polycrystalline superhard material comprises a first region abutting the substrate along the interface and a second region bonded to the first region. The second region defines a rake face, a cutting edge, a chamfer and at least a part of a flank face, the cutting edge being defined by an edge of the flank face joined to the chamfer, the chamfer extending between the cutting edge and the rake face. The height of the chamfer in a plane parallel to the plane through which the longitudinal axis of the polycrystalline superhard construction extends is less than the thickness of the second region. The first region comprises a material having coarser grains than the second region. There is also disclosed a method of making the same.

1 . A polycrystalline superhard construction comprising:
 a body of polycrystalline superhard material;   a substrate of hard material bonded to the body of polycrystalline superhard material along an interface;   wherein the body of polycrystalline superhard material comprises a first region and a second region, the first region abutting the substrate along the interface and the second region being bonded to the first region along a further interface,   the second region defining a rake face, a cutting edge, a chamfer and at least a part of a flank face, the cutting edge being defined by an edge of the flank face joined to the chamfer, the chamfer extending between the cutting edge and the rake face;   the first region having a first thickness and the second region having a second thickness;   the chamfer having a height in a plane parallel to the plane through which the longitudinal axis of the polycrystalline superhard construction extends, the height of the chamfer being less than the thickness of the second region;   the first region comprising a material having coarser grains than the material of the second region.   
     
     
         2 . A polycrystalline superhard construction according to  claim 1  wherein the thickness of the first region is greater than the thickness of the second region. 
     
     
         3 . A polycrystalline superhard construction according to  claim 1 , wherein the thickness of the second region is up to around 600 microns. 
     
     
         4 . A polycrystalline superhard construction according to  claim 1 , wherein the thickness of the first region is around 1200-1800 microns. 
     
     
         5 . A polycrystalline superhard construction according to  claim 1 , wherein the thickness of the second region exceeds the height of the chamfer by around between 100 to 400 microns. 
     
     
         6 . A polycrystalline superhard construction according to  claim 1 , wherein the height of the chamfer is between around 100-400 microns. 
     
     
         7 . A polycrystalline superhard construction according to  claim 1 , wherein the body of polycrystalline superhard material comprises polycrystalline diamond material. 
     
     
         8 . A polycrystalline superhard construction according to  claim 7 , wherein the average grain size of the diamond grains forming the second region in the body of polycrystalline diamond material is between around 0.1 to 10 microns. 
     
     
         9 . A polycrystalline superhard construction according to  claim 7 , wherein the average grain size of the diamond grains forming the second region in the body of polycrystalline diamond material is between around 1 to 8 microns. 
     
     
         10 . A polycrystalline superhard construction according to  claim 7 , wherein the average grain size of the diamond grains forming the second region in the body of polycrystalline diamond material is between around 3 to 6 microns. 
     
     
         11 . A polycrystalline superhard construction according to  claim 7 , wherein the average grain size of the diamond grains forming the first region in the body of polycrystalline diamond material is between around 6 to 20 microns. 
     
     
         12 . A polycrystalline superhard construction according to  claim 7 , wherein the average grain size of the diamond grains forming the first region in the body of polycrystalline diamond material is between around 8 to 17 microns. 
     
     
         13 . A polycrystalline superhard construction according to  claim 7 , wherein the average grain size of the diamond grains forming the first region in the body of polycrystalline diamond material is between around 6 to 17 microns. 
     
     
         14 . A polycrystalline superhard construction according to  claim 1 , wherein the chamfer angle is approximately 45°. 
     
     
         15 . A polycrystalline superhard construction according to  claim 1 , wherein the interface between the first region and the substrate is substantially non-planar. 
     
     
         16 . A polycrystalline superhard construction according to  claim 1 , wherein the substrate comprises cemented carbide. 
     
     
         17 . A cutter for boring into the earth comprising the polycrystalline superhard construction according to  claim 1 . 
     
     
         18 . A PCD element for a rotary shear bit for boring into the earth, for a percussion drill bit or for a pick for mining or asphalt degradation, comprising the polycrystalline superhard construction of  claim 1 . 
     
     
         19 . A drill bit or a component of a drill bit for boring into the earth, comprising a polycrystalline superhard construction according to  claim 1 . 
     
     
         20 . A method for making a polycrystalline superhard construction as claimed in  claim 1 , the method including:
 providing a first plurality of aggregate masses comprising diamond grains having a first mean size, at least one second aggregate mass comprising diamond grains having a second mean size; arranging the first aggregate mass on the second aggregate mass to form a pre-sinter assembly together with a body of material for forming a substrate; the first region comprising a material having coarser grains than the material of the second region; and   treating the pre-sinter assembly in the presence of a catalyst material for diamond at an ultra-high pressure and high temperature at which diamond is more thermodynamically stable than graphite to sinter together the diamond grains and a substrate bonded thereto along an interface to form an integral PCD construction comprising a first region of PCD bonded to a second region of PCD, the first region being bonded to the substrate; the first region having a first thickness and the second region having a second thickness;   the second region defining a rake face, a cutting edge, and at least a part of a flank face;   the method further comprising:   forming a chamfer in the flank face, the cutting edge being defined by an edge of the flank face joined to the chamfer, the chamfer extending between the cutting edge and the rake face, the chamfer having a height in a plane parallel to the plane through which the longitudinal axis of the superhard construction extends, the height of the chamfer being less than the thickness of the second region.