Polycrystalline Diamond Cutting Elements Having lead or Lead Alloy Additions

Abstract

Polycrystalline diamond cutting elements having enhanced thermal stability, drill bits incorporating the same, and methods of making the same are disclosed herein. In one embodiment, a cutting element includes a substrate having a metal carbide and a polycrystalline diamond body bonded to the substrate. The polycrystalline diamond body includes a plurality of diamond grains bonded to adjacent diamond grains by diamond-to-diamond bonds and a plurality of interstitial regions positioned between adjacent diamond grains. At least a portion of the plurality of interstitial regions comprise lead or lead alloy, a catalyst material, metal carbide, or combinations thereof. At least a portion of the plurality of interstitial regions comprise lead or lead alloy that coat portions of the adjacent diamond grains such that the lead or lead alloy reduces contact between the diamond and the catalyst.

1 .- 11 . (canceled) 
     
     
         12 . A method of forming a cutting element, comprising:
 assembling a reaction cell comprising a plurality of diamond particles, lead or lead alloy having lead present in an amount of at least about  90  wt. % of the lead alloy, a catalyst material, and a substrate within a refractory metal container; and   subjecting the reaction cell and its contents to a high pressure high temperature sintering process to form a continuous diamond volume in which:
 the diamond particles are compacted into a densified unbonded diamond region in which at least some of the diamond particles are separated by interstitial regions; 
 the lead or lead alloy is melted and is present in a liquid state in at least some of the interstitial regions between diamond particles; and 
 the catalyst material is melted and is present in at least some of the interstitial regions between the individual diamond grains, wherein the catalyst material promotes formation of diamond-to-diamond bonds between adjacent diamond particles, 
   wherein the lead or lead alloy coats surfaces of at least a portion of the plurality of diamond particles after the high pressure high temperature sintering operation is completed.   
     
     
         13 . The method of  claim 12 , wherein the catalyst material is swept through at least a portion of the plurality of unbonded diamond particles while molten and displaces a portion of the lead or lead alloy from the interstitial regions between diamond particles. 
     
     
         14 . The method of  claim 12 , wherein the lead or lead alloy is swept through at least a portion of the plurality of unbonded diamond particles while molten. 
     
     
         15 . The method of  claim 12 , wherein the lead or lead alloy is mixed with the diamond particles prior to the step of compaction of the diamond particles. 
     
     
         16 . The method of  claim 12 , wherein the volume of lead or lead alloy introduced to the diamond particles is less than a volume of interstitial regions between diamond particles. 
     
     
         17 . The method of  claim 12 , wherein when the lead or lead alloy and the catalyst material are held at a temperature above the melting or liquidus temperature of the catalyst material, the lead or lead alloy has a lower viscosity than the catalyst material. 
     
     
         18 . The method of  claim 12 , further comprising subjecting the diamond volume to a leaching process in which a leaching agent removes at least portions of the catalyst material and lead or lead alloy from the interstitial regions of the diamond volume. 
     
     
         19 . The method of  claim 12 , wherein the diamond grains have higher wettability with the catalyst material than the lead or lead alloy when both are molten. 
     
     
         20 . (canceled)