Polycrystalline diamond cutting elements with engineered porosity and method for manufacturing such cutting elements

Abstract

A method for facilitating infiltration of an infiltrant material into a TSP material during re-bonding of the TSP material to a substrate, by enhancing the porosity of the TSP material near the interface with the substrate is provided. Cutting elements formed by such method and downhole tools including such cutting elements are also provided.

What is claimed is: 
     
         1 . A method of forming a thermally stable polycrystalline diamond cutting element, comprising:
 mixing diamond particles and a filler material to create a diamond powder mixture, wherein the diamond powder mixture comprises a first portion with the filler material and a second portion with less filler material than the first portion, the first portion being at least 25% of a volume of the diamond powder mixture;   sintering the diamond powder mixture at high temperature and high pressure to form a polycrystalline diamond material;   removing the filler material from the polycrystalline diamond material to form a thermally stable polycrystalline diamond material having a differential porosity of at least 1.6% between the first and second portions; and   bonding the thermally stable material to a substrate, wherein bonding comprises infiltrating the first portion with an infiltrant material from the substrate.   
     
     
         2 . The method of  claim 1 , wherein bonding comprises arranging the thermally stable material and the substrate such that the first portion of the thermally stable material is proximate the substrate. 
     
     
         3 . The method of  claim 1 , wherein the filler material comprises cobalt. 
     
     
         4 . The method of  claim 1 , wherein the filler material comprises tungsten carbide. 
     
     
         5 . The method of  claim 4 , wherein the filler material comprises 5% by weight tungsten carbide in the first portion. 
     
     
         6 . The method of  claim 1 , wherein mixing the diamond particles and the filler material comprises forming a gradient of an amount of filler material in the diamond powder mixture. 
     
     
         7 . The method of  claim 1 , wherein the first portion forms a first layer of the thermally stable material nearest the substrate, and the second portion forms a second layer of the thermally stable material opposite the substrate. 
     
     
         8 . The method of  claim 7 , wherein the first and second layers are approximately the same size. 
     
     
         9 . The method of  claim 1 , wherein the first portion of the diamond powder mixture has a domed shape. 
     
     
         10 . The method of  claim 1 , wherein the second portion comprises a depression and wherein the first portion comprises a projection, wherein the projection is received in said depression. 
     
     
         11 . The method of  claim 1 , wherein the first portion has at least 4% filler material by weight. 
     
     
         12 . The method of  claim 1 , wherein, after removing the filler material, the first portion comprises pores occupying about 9% of a volume of the first portion. 
     
     
         13 . The method of  claim 1 , wherein the differential porosity is at least 2.6%.