Impregnated drill bits and methods for making the same

Abstract

An impregnated cutting structure that includes a plurality of first encapsulated particles, each first encapsulated particle comprising a first abrasive particle encapsulated by a first matrix material shell; and a plurality of second encapsulated particles, the second encapsulated particles comprising a second abrasive particle encapsulated by a second matrix material shell, wherein the first encapsulated particles and the second encapsulated particles have at least one property difference is disclosed.

1 . An impregnated cutting structure comprising:
 a plurality of first encapsulated particles, each first encapsulated particle comprising a first abrasive particle encapsulated by a first matrix material shell; and   a plurality of second encapsulated particles, the second encapsulated particles comprising a second abrasive particle encapsulated by a second matrix material shell, wherein the first encapsulated particles and the second encapsulated particles have at least one property difference.   
     
     
         2 . The cutting structure of  claim 1 , wherein the first matrix material and second matrix material comprise different wear rates. 
     
     
         3 . The cutting structure of  claim 2 , wherein the first matrix material is softer than the second matrix material. 
     
     
         4 . The cutting structure of  claim 1 , wherein the first encapsulated particle is coarser than the second encapsulated particle. 
     
     
         5 . The cutting structure of  claim 1 , wherein the first abrasive particle is coarser than the second abrasive particle. 
     
     
         6 . The cutting structure of  claim 1 , wherein the first abrasive particle has less compressive strength than the second abrasive particle. 
     
     
         7 . The cutting structure of  claim 1 , wherein the encapsulating first matrix material shell is thicker than the encapsulating second matrix material shell. 
     
     
         8 . The cutting structure of  claim 1 , wherein at least one of the first abrasive particle and second abrasive particle have a retention coating deposited thereon. 
     
     
         9 . The cutting structure of  claim 8 , wherein the first abrasive particle has a weaker retention coating deposited thereon as compared to the second abrasive particle. 
     
     
         10 . The cutting structure of  claim 1 , where the first and the second matrix materials individually comprise at least one of sintered tungsten carbide, cast tungsten carbide, and carbides of tungsten, vanadium, chromium, titanium, tantalum, and niobium. 
     
     
         11 . The cutting structure of  claim 1 , where the first and the second matrix materials individually comprise at least one of copper, cobalt, nickel, iron, and alloys thereof. 
     
     
         12 . The cutting structure of  claim 1 , wherein the first and second abrasive particles individually comprise at least one of synthetic diamond, natural diamond, TSP, and CBN. 
     
     
         13 . The cutting structure of  claim 1 , further comprising:
 a plurality of third encapsulated particles, each third encapsulated particle comprises a third abrasive particle encapsulated by a third matrix material shell.   
     
     
         14 . A drill bit, comprising:
 a bit body; and   a plurality of ribs formed in the bit body, wherein at least one rib comprises:
 a plurality of first encapsulated particles, each first encapsulated particle comprising a first abrasive particle encapsulated by a first matrix material shell; 
 a plurality of second encapsulated particles, each second encapsulated particle comprising a second abrasive particle encapsulated by a second matrix material shell, wherein the first encapsulated particles and the second encapsulated particles comprise at least one property difference therebetween. 
   
     
     
         15 . The drill bit of  claim 14 , wherein the first matrix material and second matrix material comprise different wear properties. 
     
     
         16 . The drill bit of  claim 15 , further comprising:
 a third matrix material infiltrated between the first and second encapsulated materials.   
     
     
         17 . The drill bit of  claim 14 , wherein a consolidated insert comprising the first and second encapsulated particles are brazed or cast into the rib. 
     
     
         18 . A drill bit, comprising:
 a bit body; and   a plurality of ribs formed in the bit body, wherein a portion of at least one rib has a height to width ratio of greater than about 1.75 with a minimum diamond concentration of 100 and comprises:
 a plurality of first encapsulated particles, each first encapsulated particle comprising a first abrasive particle encapsulated by a first matrix material shell. 
   
     
     
         19 . The drill bit of  claim 18 , wherein the at least one rib further comprises:
 a plurality of second encapsulated particles, each second encapsulated particle comprising a second abrasive particle encapsulated by a second matrix material shell, wherein the first encapsulated particles and the second encapsulated particles comprise at least one property difference therebetween.   
     
     
         20 . The drill bit of  claim 19 , wherein the first matrix material and second matrix material comprise different wear properties. 
     
     
         21 . The drill bit of  claim 19 , wherein the at least one rib further comprises:
 a third matrix material infiltrated between the first and second encapsulated materials.   
     
     
         22 . A method of forming an impregnated cutting structure comprising:
 loading a plurality of first encapsulated particles and a plurality of second encapsulated particles into a mold cavity, each first encapsulated particle comprising a first abrasive particle encapsulated by a first matrix material shell and each second encapsulated particle comprising a second abrasive particle encapsulated by a second matrix material shell, wherein the first encapsulated particles and the second encapsulated particles comprise at least one property difference therebetween; and   heating the mold contents to form an impregnated cutting structure.   
     
     
         23 . The method of  claim 22 , further comprising:
 applying pressure to the first and second encapsulated particles within the mold.   
     
     
         24 . The method of  claim 22 , further comprising:
 loading a third matrix material into the mold with the first and second encapsulated particles; and   infiltrating the mold contents with a infiltrating binder.   
     
     
         25 . The method of  claim 22 , wherein the at least one property difference comprises at least one of different wear rates between the matrix materials, different toughness between the matrix materials, different size of the encapsulated particles, different size of the abrasive particles, different compressive strengths between the abrasive particles, different shell thicknesses, and presence or type of retention coatings.