Methods for pre-sharpening impregnated cutting structures for bits, resulting cutting structures and drill bits so equipped

Abstract

Processes for pre-sharpening cutting structures comprising particles of superabrasive material such as diamond grit, dispersed in a metal matrix material such as cemented tungsten carbide. Matrix material may be removed from a surface of a cutting structure to a desired depth to expose superabrasive particles within the matrix material adjacent the surface, and to increase exposure of partially exposed superabrasive particles at the surface. Electrodischarge machining (EDM), laser machining, electrolytic etching and chemical etching may also be employed. Pre-sharpened cutting structures are also disclosed.

What is claimed is: 
     
         1 . A method of pre-sharpening an impregnated cutting structure for subterranean use, the method comprising:
 providing the impregnated cutting structure including superabrasive material particles dispersed in a matrix material; and   removing a depth of the matrix material of at least one formation-engaging surface to at least one of enhance exposure of exposed superabrasive particles to an increased height above the matrix material or expose portions of unexposed superabrasive particles adjacent the matrix material.   
     
     
         2 . The method of  claim 1 , wherein removing the depth of the matrix material further comprises removing a substantially uniform depth of the matrix material while minimizing damage to the superabrasive material particles to both enhance exposure of the exposed superabrasive particles to the increased height above the matrix material and expose portions of the unexposed superabrasive particles adjacent the matrix material. 
     
     
         3 . The method of  claim 1 , wherein removing the depth of the matrix material further comprises at least one of machining, electrolytic etching or chemical etching the matrix material. 
     
     
         4 . The method of  claim 3 , wherein removing the depth of the matrix material comprises removing the depth of matrix material by machining, and machining comprises at least one of electrodischarge machining or laser machining the matrix material. 
     
     
         5 . The method of  claim 1 , wherein removing the depth of the matrix material includes enhancing aggressiveness of the at least one formation-engaging surface of the impregnated cutting structure prior to use. 
     
     
         6 . The method of  claim 1 , wherein providing the impregnated cutting structure including the superabrasive material particles dispersed in the matrix material further comprises bonding the superabrasive material particles to the matrix material through at least one refractory material coating applied to the superabrasive material particles. 
     
     
         7 . A pre-sharpened impregnated cutting structure for subterranean use, comprising:
 a plurality of superabrasive material particles dispersed in a matrix material;   at least one formation-engaging surface located on the pre-sharpened impregnated cutting structure; and   at least a portion of the superabrasive material particles exhibiting substantial exposure above the at least one formation-engaging surface resulting from removing a depth of matrix material prior to use.   
     
     
         8 . The cutting structure of  claim 7 , wherein the plurality of superabrasive material particles comprises at least one of natural, synthetic or a combination of natural and synthetic superabrasive material particles. 
     
     
         9 . The cutting structure of  claim 7 , wherein:
 the depth of matrix material removed prior to use includes a substantially uniform depth of matrix material; and   the substantially uniform depth of matrix material is dependent on a grit size of the plurality of superabrasive material particles.   
     
     
         10 . The cutting structure of  claim 7 , wherein the matrix material comprises a metal matrix material comprising at least one of a tungsten carbide or a cobalt-cemented tungsten carbide. 
     
     
         11 . The cutting structure of  claim 10 , wherein the plurality of superabrasive material particles is bonded to the metal matrix material through at least one coating applied to the plurality of superabrasive material particles, the at least one coating comprising at least one of a refractory metal, a refractory metal carbide or a refractory metal oxide. 
     
     
         12 . The cutting structure of  claim 11 , wherein:
 the plurality of superabrasive material particles is spaced substantially uniform within and mutually separated by the metal matrix material, and   the at least one coating is configured to enable the plurality of superabrasive material particles to exhibit substantial exposure above the at least one formation-engaging surface.   
     
     
         13 . The cutting structure of  claim 7 , wherein the pre-sharpened impregnated cutting structure comprises a cylindrical shape having at least one of a flat end surface, a tapered end surface or an arcuate end surface. 
     
     
         14 . The cutting structure of  claim 7 , further comprising at least one discrete protrusion extending from an outer end surface of the pre-sharpened impregnated cutting structure, wherein the at least one discrete protrusion is coated with a refractory material and is bonded to the matrix material of the pre-sharpened impregnated cutting structure. 
     
     
         15 . A bit for subterranean use, comprising:
 a plurality of pre-sharpened impregnated cutting structures comprising:
 a matrix material; 
 at least one formation-engaging surface located on the plurality of pre-sharpened impregnated cutting structures; and 
 superabrasive material particles dispersed in the matrix material and exhibiting substantial exposure above the at least one formation-engaging surface resulting from removing a depth of the matrix material prior to use. 
   
     
     
         16 . The bit of  claim 15 , wherein the plurality of pre-sharpened impregnated cutting structures is configured for at least one of drilling or enlarging wellbores through subterranean formations. 
     
     
         17 . The bit of  claim 15 , wherein the matrix material further comprises a wear-resistant metal matrix material, the superabrasive material particles being metallurgically bonded to the wear-resistant metal matrix material through a coating. 
     
     
         18 . The bit of  claim 15 , wherein the plurality of pre-sharpened impregnated cutting structures comprises at least one of sharpened prior to being secured to the bit or sharpened after being integrally formed on the bit prior to using the bit in a wellbore. 
     
     
         19 . The bit of  claim 15 , wherein at least some pre-sharpened impregnated cutting structures of the plurality of pre-sharpened impregnated cutting structures are discrete and are configured and located to provide a progressively increasing contact area between the superabrasive material particles and a formation. 
     
     
         20 . The bit of  claim 19 , wherein the plurality of discrete pre-sharpened impregnated cutting structures further comprises protrusions extending from the at least one formation-engaging surface, the protrusions having at least one of a triangular, square, rectangular or rounded cross-sectional geometry.