Polycrystalline diamond composite compact element, tools incorporating same and method for making same

Abstract

The invention relates to a PCD composite compact element comprising a PCD structure integrally bonded at an interface to a cemented carbide substrate; the PCD structure comprising coherently bonded diamond grains having a mean size no greater than 15 microns; the cemented carbide substrate comprising carbide particles dispersed in a metallic binder, the carbide particles comprising a carbide compound of a metal; wherein the ratio of the amount of metallic binder to the amount of the metal at points in the substrate deviates from a mean value by at most 20 percent of the mean value. The invention further relates to a method for making a PDC compact element comprising a PCD structure integrally bonded to a substrate formed of cemented carbide; the method including introducing a source of excess carbon to the substrate at a bonding surface of the substrate to form a carburised substrate; contacting an aggregated mass of diamond grains with the carburised substrate; and sintering the diamond grains in the presence of a solvent/catalyst material for diamond; wherein the mean size of the diamond grains in the aggregated mass is no greater than 30 microns.

What is claimed is: 
     
         1 . A method for making a polycrystalline diamond composite (PDC) compact element comprising a polycrystalline diamond (PCD) structure integrally bonded to a substrate formed of cemented carbide; the method including introducing a source of excess carbon to the substrate at or proximate a bonding surface of the substrate to form a carburised substrate or carburised substrate assembly; contacting an aggregated mass of diamond grains with the carburised substrate or carburised substrate assembly adjacent or proximate the bonding surface to form an unbonded assembly; and sintering the diamond grains in the presence of a solvent/catalyst material for diamond at a temperature and pressure at which diamond is thermodynamically stable to form POD; wherein the mean size of the diamond grains in the aggregated mass is no greater than about 30 microns. 
     
     
         2 . A method according to  claim 1 , including introducing at least 0.1 weight percent source of excess carbon to the substrate at or proximate the bonding surface of the substrate wherein the weight percent is expressed as of the total substrate material within the region in which the carbon is introduced. 
     
     
         3 . A method according to  claim 1 , including forming the aggregated mass from diamond grains having a multi-modal size distribution. 
     
     
         4 . A method according to  claim 1 , wherein the source of excess carbon is in the form of carbon black powder or graphite. 
     
     
         5 . A method according to  claim 1 , including introducing diamond to the substrate at or proximate the bonding surface of the substrate and converting at least some of the diamond into graphite to serve as a source of excess carbon. 
     
     
         6 . A method according to  claim 1 , including combining source of excess carbon in particulate or granular form with raw materials for the cemented carbide, forming the combination into a substantially self-supporting green body, and sintering the green body at a pressure at which diamond is not thermodynamically stable. 
     
     
         7 . A method according to  claim 1 , including combining diamond grains with raw materials for cemented carbide, forming the combination into a substantially self-supporting green body; subjecting the green body to a temperature of at least 500 degrees centigrade and a pressure at which diamond is not thermodynamically stable. 
     
     
         8 . A method according to  claim 1 , including introducing refractory metal carbide particles into the aggregated mass of diamond grains, the refractory metal carbide particles being selected from the group consisting of tungsten carbide, tantalum carbide, niobium carbide and vanadium carbide and/or introducing a refractory metal precursor for metal carbide into the aggregated mass of diamond grains, the refractory metal being selected from the group consisting of tungsten, tantalum, niobium and vanadium in non-carbide compound or in elemental form. 
     
     
         9 . A method according to  claim 1 , wherein the step of introducing the source of excess carbon comprises dispersing the source of excess carbon is throughout the volume of the carburised substrate or carburised substrate assembly. 
     
     
         10 . A method according to  claim 1 , wherein prior to the step of contacting the aggregated mass of diamond grains with the carburised substrate or carburised substrate assembly the method further comprising forming the carburised substrate by sintering a mixture comprising tungsten carbide grains, a binder material and the source of excess carbon. 
     
     
         11 . A method according to  claim 1 , wherein the step of introducing the source of excess carbon comprises introducing no greater than about 10 weight percent of the of the source of excess carbon in the surface region or the substrate. 
     
     
         12 . A method according to  claim 1 , wherein the content of the source of excess carbon within the surface region or throughout the entire carburised substrate is at least about 0.1 weight percent of the surface region or substrate. 
     
     
         13 . A method according to  claim 1 , wherein the content of the source of excess carbon within the surface region or throughout the entire carburised substrate is at least about 0.3 weight percent of the surface region or substrate. 
     
     
         14 . A method according to  claim 1 , wherein the surface region extends to a depth of at least about 1 mm, at least about 2 mm, or even at least 3 mm from the bonding surface. 
     
     
         15 . A method according to  claim 1 , wherein the source of excess carbon is introduced in the form of a gas. 
     
     
         16 . A method according to  claim 1 , comprising combining the source of excess carbon in particulate or granular form with raw materials for the cemented carbide, forming the combination into a substantially self-supporting green body, and sintering the green body at a pressure at which diamond is not thermodynamically stable to form the carburised substrate