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.

1 . A polycrystalline diamond (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 about 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 about 20 percent of the mean value. 
     
     
         2 . A PCD composite compact element according to  claim 1 , wherein the metal of the carbide particles is a refractory metal selected from the group consisting of W, Ti, Ta, and Cr. 
     
     
         3 . A PCD composite compact element according to either one of  claims 1  and  2 , wherein the substrate has a surface region extending from the interface to a depth of at least 1 mm, the region containing diamond particles dispersed within it. 
     
     
         4 . A PCD composite compact element according to any one of  claims 1  to  3 , wherein the PCD structure comprises a first and a second region, the mean size of the diamond grains of the first region being greater than the mean size of the diamond grains in the second region; the first region being proximate the substrate and the second region being remote from the substrate. 
     
     
         5 . A PCD composite compact element according to any one of  claims 1  to  4 , wherein the ratio of the amount of metallic binder to the amount carbon at points in the PCD structure deviates from a mean value by at most 20 percent of the mean value, from the interface to a depth of at least 0.5 mm into the PCD structure. 
     
     
         6 . 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 PCD; wherein the mean size of the diamond grains in the aggregated mass is no greater than about 30 microns. 
     
     
         7 . A method according to  claim 6 , 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. 
     
     
         8 . A method according to any one of  claims 6  and  7 , including forming the aggregated mass from diamond grains having a multi-modal size distribution. 
     
     
         9 . A method according to any one of  claims 6  to  8 , wherein the source of excess carbon is in the form of carbon black powder or graphite. 
     
     
         10 . A method according to any one of  claims 6  to  9 , 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. 
     
     
         11 . A method according to any one of  claims 6  to  10 , 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. 
     
     
         12 . A method according to any one of  claims 6  to  11 , 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. 
     
     
         13 . A method according to any one of  claims 6  to  12 , 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. 
     
     
         14 . A PCD cutter insert for a drill bit, the PCD cutter insert comprising a PCD composite compact element according to any one of  claims 1  to  5 . 
     
     
         15 . A drill bit for boring into the earth comprising a PCD cutter insert according to  claim 14 .