Non-uniform polycrystalline composite and its method of manufacture

Abstract

A polycrystalline diamond composite including a generally circular sintered polycrystalline cutting disc and a refractory substrate operationally connected to the polycrystalline cutting disc. The polycrystalline cutting disc further includes a plurality of coarse diamond grains and a plurality of fine diamond grains. The plurality fine diamond grains are concentrated in an annulus positioned to define an outer edge of the polycrystalline cutting disc.

What is claimed is: 
     
         1 . A polycrystalline diamond composite comprising:
 a generally circular sintered polycrystalline cutting disc; and   a refractory substrate operationally connected to the polycrystalline cutting disc;   wherein the polycrystalline cutting disc further comprises:
 a plurality of coarse diamond grains; and 
 a plurality of fine diamond grains; and 
 wherein the plurality fine diamond grains are concentrated in an annulus positioned to define an outer edge of the polycrystalline cutting disc. 
   
     
     
         2 . The polycrystalline diamond composite of  claim 1 , wherein the polycrystalline cutting disc has a first circular flat surface and a second, oppositely disposed flat circular surface spaced from and oriented parallel to the first circular flat surface; wherein the distance between the first and second circular flat surfaces defines a disc thickness; and wherein the annulus extends from the first surface toward the second surface. 
     
     
         3 . The polycrystalline diamond composite of  claim 2 , wherein the annulus is thinner than the disc thickness. 
     
     
         4 . The polycrystalline diamond composite of  claim 2 , wherein the a plurality of fine diamond grains are concentrated in the annulus positioned on the first circular flat surface and to positioned to define the outer edge of the polycrystalline cutting disc, in a first band extending from a first point on the outer edge of the polycrystalline cutting disc to a second, spaced point on the outer edge of the polycrystalline cutting disc, and in a second band extending from a third, spaced point on the outer edge of the polycrystalline cutting disc to a fourth, spaced point on the outer edge of the polycrystalline cutting disc. 
     
     
         5 . The polycrystalline diamond composite of  claim 4  wherein the first and second bands are oriented perpendicularly to one another; and wherein the first and second bands bisect the first circular flat surface. 
     
     
         6 . The polycrystalline diamond composite of  claim 4  wherein the first and second bands are thinner than the disc thickness. 
     
     
         7 . A method for attaching a polycrystalline diamond portion to a substrate comprising:
 a) positioning at least one polycrystalline diamond layer in mechanical communication with a substrate to define a bilayer;   b) heating the bilayer to a temperature sufficient to at least partially melt the substrate to yield molten substrate material;   c) applying sufficient pressure to the bilayer to urge penetration of molten substrate material into the polycrystalline diamond layer; and   d) bonding the polycrystalline diamond layer to the substrate.   
     
     
         8 . The method of  claim 7  wherein the substrate is tungsten carbide. 
     
     
         9 . The method of  claim 7  wherein during b), the bilayer is heated to about 1500° C. 
     
     
         10 . The method of  claim 7  wherein during c) the bilayer is under about 55 Kbar. 
     
     
         11 . The method of  claim 7  wherein the molten substrate material contains cobalt. 
     
     
         12 . The method of  claim 7  wherein the substrate is multilayered. 
     
     
         13 . The method of  claim 7  wherein the polycrystalline layer further comprises a non-uniform mixture of a coarse diamond grains and fine diamond grains. 
     
     
         14 . The method of  claim 13 , wherein a plurality of fine diamond grains defines an outer annulus around an outer the polycrystalline diamond layer. 
     
     
         15 . The method of  claim 7  wherein the polycrystalline diamond layer is pre-sintered. 
     
     
         16 . The method of  claim 7  wherein before c), the polycrystalline diamond layer is substantially metal-free. 
     
     
         17 . The method of  claim 7  wherein steps a) and b) occur substantially simultaneously.