Methods of forming earth-boring rotary drill bits

Abstract

Methods of forming earth-boring rotary drill bits include providing a bit body, providing a shank that is configured for attachment to a drill string, and attaching the shank to the bit body. Providing a bit body includes providing a green powder component having a first region having a first composition and a second region having a second, different composition, and at least partially sintering the green powder component. Other methods include providing a powder mixture, pressing the powder mixture to form a green component, and sintering the green component to a final density. A shank is provided that includes an aperture, and a feature is machined in a surface of the bit body. The aperture is aligned with the feature, and a retaining member is inserted through the aperture. An earth-boring bit includes a bit body comprising a particle-matrix composite material including a plurality of hard particles dispersed throughout a matrix material. A shank is attached to the bit body using a retaining member.

1 . A method of forming a fixed cutter earth-boring rotary drill bit, the method comprising:
 providing a bit body comprising:
 pressing a powder mixture to form a green bit body; 
 sintering the green bit body and forming the bit body, the bit body comprising a particle-matrix composite material having a final density; and 
   fixedly attaching a shank to the bit body such that relative movement between the shank and the bit body is at least substantially precluded during drilling operations, the shank configured for attachment to a drill string, fixedly attaching the shank to the bit body comprising:
 positioning at least a portion of the shank and at least a portion of the bit body such that one of the at least a portion of the shank and the at least a portion of the bit body is located circumferentially about the other of the at least a portion of the shank and the at least a portion of the bit body; 
 providing a retaining member at an interface between the at least a portion of the shank and the at least a portion of the bit body, mechanical interference between the retaining member, the at least a portion of the shank, and the at least a portion of the bit body precluding longitudinal separation between the shank and the bit body. 
   
     
     
         2 . The method of  claim 1 , wherein positioning at least a portion of the shank and at least a portion of the bit body such that one of the at least a portion of the shank and the at least a portion of the bit body is located circumferentially about the other of the at least a portion of the shank and the at least a portion of the bit body comprises positioning at least a portion of an inner surface of the shank circumferentially about a portion of the bit body. 
     
     
         3 . The method of  claim 2 , further comprising:
 providing an aperture extending at least partially through the shank; and   providing at least one recess in the bit body; and   wherein providing the retaining member at the interface between the at least a portion of the shank and the at least a portion of the bit body comprises positioning the retaining member within the aperture extending at least partially through the shank and within the at least one recess in the bit body.   
     
     
         4 . The method of  claim 3 , wherein fixedly attaching the shank to the bit body further comprises selecting the retaining member to comprise an elongated rod. 
     
     
         5 . The method of  claim 4 , wherein fixedly attaching the shank to the bit body further comprises positioning the elongated rod to extend through the aperture extending at least partially through the shank, through the at least one recess in the bit body, and through another aperture extending at least partially through the shank. 
     
     
         6 . The method of  claim 1 , wherein providing the retaining member at the interface between the at least a portion of the shank and the at least a portion of the bit body comprises providing a substantially uniform gap between at least one surface of the shank and at least one surface of the bit body. 
     
     
         7 . The method of  claim 6 , wherein providing the substantially uniform gap comprises forming the substantially uniform gap to be between about 50 microns (0.002 inch) and about 150 microns (0.006 inch). 
     
     
         8 . The method of  claim 1 , further comprising providing a brazing alloy between the at least a portion of the shank and the at least a portion of the bit body. 
     
     
         9 . The method of  claim 1 , further comprising welding an interface between the shank and the bit body. 
     
     
         10 . The method of  claim 1 , further comprising:
 formulating the powder mixture to comprise:
 a plurality of particles comprising a matrix material, the matrix material selected from the group consisting of cobalt-based alloys, iron-based alloys, nickel-based alloys, cobalt and nickel-based alloys, iron and nickel-based alloys, iron and cobalt-based alloys, aluminum-based alloys, copper-based alloys, magnesium-based alloys, and titanium-based alloys; and 
 a plurality of hard particles comprising a material selected from diamond, boron carbide, boron nitride, aluminum nitride, and carbides or borides of the group consisting of W, Ti, Mo, Nb, V, Hf, Zr, and Cr. 
   
     
     
         11 . The method of  claim 10 , wherein formulating the powder mixture further comprises selecting the plurality of particles comprising the matrix material to comprise a matrix material selected from the group consisting of nickel-based alloys, cobalt-based alloys, and nickel and cobalt-based alloys. 
     
     
         12 . The method of  claim 1 , further comprising machining the at least one feature in a surface of the bit body. 
     
     
         13 . The method of  claim 12 , wherein machining the at least one feature in the surface of the bit body comprises machining at least one groove in the surface of the bit body, the method further comprising positioning at least a portion of the retaining member within the at least one groove. 
     
     
         14 . The method of  claim 1 , wherein sintering the green bit body comprises:
 partially sintering the green bit body to form a brown bit body;   machining at least one feature in the brown bit body; and   sintering the brown bit body to the final density.   
     
     
         15 . The method of  claim 1 , wherein sintering the green bit body comprises subliquidus phase sintering. 
     
     
         16 . The method of  claim 1 , wherein pressing the powder mixture to form the green bit body comprises isostatically pressing the powder mixture. 
     
     
         17 . The method of  claim 16 , wherein isostatically pressing the powder mixture comprises pressing the powder mixture with a liquid. 
     
     
         18 . The method of  claim 16 , wherein isostatically pressing the powder mixture comprises pressing the powder mixture with pressure greater than about 35 megapascals (about 5,000 pounds per square inch). 
     
     
         19 . A fixed cutter earth-boring rotary drill bit, comprising:
 a bit body at least substantially comprised of a pressed and sintered bit body comprising a particle-matrix composite material; and   a shank configured for attachment to a drill string fixedly attached to the bit body such that relative movement between the shank and the bit body is at least substantially precluded during drilling operations, at least a portion of the shank and at least a portion of the bit body positioned such that one of the at least a portion of the shank and the at least a portion of the bit body is located circumferentially about the other of the at least a portion of the shank and the at least a portion of the bit body; and   a retaining member at an interface between the at least a portion of the shank and the at least a portion of the bit body;   wherein mechanical interference between the retaining member, the at least a portion of the shank, and the at least a portion of the bit body precludes longitudinal separation between the shank and the bit body.   
     
     
         20 . The fixed cutter earth-boring rotary drill bit of  claim 19 , wherein mechanical interference between the retaining member, the at least a portion of the shank, and the at least a portion of the bit body precludes relative rotational movement between the shank and the bit body