Roller cones having non-integral cutting structures, drill bits including such cones, and methods of forming same

Abstract

Methods of manufacturing roller cones for drill bits include providing both integral teeth and non-integral teeth on the roller cones. A layer of hardfacing may be applied to the integral teeth. Non-integral teeth may be formed on a body of a cone, or they may be separately formed from the body and attached thereto. In some embodiments, the non-integral teeth are formed by building-up the non-integral teeth from hardfacing material. Roller cones and earth-boring tools are formed using such methods.

1 . A method of forming a roller cone for an earth-boring rotary drill bit, comprising:
 forming at least two integral teeth on a cone body with at least one gap therebetween; and   providing at least one non-integral tooth on the cone body in the at least one gap.   
     
     
         2 . The method of  claim 1 , further comprising applying a hardfacing material to at least one surface of each tooth of the at least two integral teeth. 
     
     
         3 . The method of  claim 1 , wherein forming the at least two integral teeth on the cone body comprises:
 forming a first row of integral teeth extending circumferentially about a rotational axis of the cone body; and   forming a second row of integral teeth extending circumferentially about a rotational axis of the cone body; and   wherein the at least one gap comprises at least one gap between a tooth of the first row of integral teeth and a tooth of the second row of integral teeth.   
     
     
         4 . The method of  claim 1 , wherein forming the at least two integral teeth on the cone body comprises forming at least one row of integral teeth extending circumferentially about a rotational axis of the cone body, and wherein the at least one gap between the at least two integral teeth comprises at least one gap between two teeth of the at least one row of integral teeth. 
     
     
         5 . The method of  claim 1 , wherein providing the at least one non-integral tooth on the cone body in the at least one gap comprises providing two or more non-integral teeth on the cone body in the at least one gap. 
     
     
         6 . The method of  claim 1 , further comprising:
 marking an area on a surface of the cone body in the at least one gap; and   providing the at least one non-integral tooth on the marked area on the surface of the cone body in the at least one gap.   
     
     
         7 . The method of  claim 6 , wherein marking an area on the surface of the cone body comprises forming a stub on the cone body in the at least one gap, and wherein forming the at least one non-integral tooth comprises forming the at least one non-integral tooth on the stub. 
     
     
         8 . The method of  claim 1 , wherein forming the at least one non-integral tooth on the cone body in the at least one gap comprises:
 successively depositing multiple layers of hardfacing material over the cone body in the at least one gap; and   forming the at least one non-integral tooth from the multiple layers of hardfacing material.   
     
     
         9 . The method of  claim 8 , further comprising robotically manipulating the cone body while using a welding torch to deposit the multiple layers of hardfacing material. 
     
     
         10 . The method of  claim 9 , further comprising:
 using the welding torch to generate a plasma-transferred arc; and   pulsing a current of the plasma-transferred arc as the welding torch is used to deposit the multiple layers of hardfacing material.   
     
     
         11 . The method of  claim 7 , wherein successively depositing the multiple layers of hardfacing material comprises:
 forming an interior region of the at least one non-integral tooth from a first hardfacing composition; and   forming an exterior region of the at least one non-integral tooth from a second hardfacing composition differing from the first hardfacing composition.   
     
     
         12 . The method of  claim 7 , further comprising removing at least a portion of the hardfacing material from the at least one non-integral tooth to provide the at least one non-integral tooth with a desired shape. 
     
     
         13 . The method of  claim 12 , further comprising placing a template over the at least one non-integral tooth and machining the at least one non-integral tooth to conform to the template. 
     
     
         14 . The method of  claim 1 , wherein providing at least one non-integral tooth on the cone body in the at least one gap comprises:
 forming the at least one non-integral tooth separately from the cone body; and   attaching the at least one non-integral tooth to the cone body.   
     
     
         15 . The method of  claim 14 , wherein forming the at least one non-integral tooth comprises:
 injecting a powder mixture comprising hard particles and particles of a metal-matrix material into a mold cavity to form a green body; and   sintering the green body to a desired final density to form the at least one non-integral tooth.   
     
     
         16 . The method of  claim 14 , wherein attaching the at least one non-integral tooth to the cone body comprises bonding the at least one non-integral tooth to the cone body with a metallic material. 
     
     
         17 . The method of  claim 16 , wherein bonding the at least one non-integral tooth to the cone body with the metallic material comprises:
 providing the metallic material between the at least one non-integral tooth and the cone body; and   co-sintering the at least one non-integral tooth, the cone body, and the metallic material.   
     
     
         18 . A method of forming a roller cone for an earth-boring rotary drill bit, comprising:
 forming at least two integral disk cutters on a cone body to extend circumferentially on the cone body about a rotational axis of the cone body;   leaving at least one gap between the at least two integral disk cutters; and   providing at least one non-integral disk cutter on the cone body in the at least one gap.   
     
     
         19 . The method of  claim 18 , wherein providing the at least one non-integral disk cutter on the cone body in the at least one gap comprises:
 depositing hardfacing material over a surface of the cone body in the at least one gap; and   forming the at least one non-integral disk cutter from the hardfacing material.   
     
     
         20 . The method of  claim 18 , further comprising forming a serrated edge on the at least one non-integral disk cutter. 
     
     
         21 . The method of  claim 20 , wherein building up the at least one non-integral tooth in the gap comprises successively depositing layers of the hardfacing material in the gap using a welding torch. 
     
     
         22 . A method of forming a roller cone for an earth-boring rotary drill bit, comprising:
 forming at least one integral disk cutter on a cone body to extend circumferentially on the cone body about a rotational axis of the cone body; and   providing at least one non-integral disk cutter on the cone body.   
     
     
         23 . A method of forming an earth-boring bit, the method comprising:
 forming a plurality of integral teeth on at least one cutter;   forming a gap between at least two adjacent integral teeth of the plurality of integral teeth;   applying a hardfacing layer to at least one surface on each of the at least two adjacent integral teeth of the plurality of integral teeth; and   depositing hardfacing material in the gap between the at least two adjacent integral teeth and building up at least one non-integral tooth in the gap using the deposited hardfacing material.   
     
     
         24 . A method of forming an earth-boring bit, the method comprising:
 forming a plurality of integral teeth on at least one cutter;   providing a gap between at least two adjacent integral teeth of the plurality of integral teeth;   applying a hardfacing layer to at least one surface on each of the at least two adjacent integral teeth of the plurality of integral teeth;   forming at least one non-integral tooth separately from the at least one cutter, comprising:
 molding a green body comprising a plurality of hard particles and a plurality of particles comprising a metallic matrix material; and 
 sintering the green body to form the non-integral tooth; and 
   bonding the at least one non-integral tooth to the at least one cutter in the gap between the at least two adjacent integral teeth with a metallic binder material.   
     
     
         25 . An earth-boring bit, comprising:
 a body having at least one bit leg;   a roller cone mounted to the at least one bit leg and rotatable on the at least one bit leg about a rotational axis;   at least one integral tooth formed on a surface of the roller cone;   a hardfacing material deposited on at least one surface of the at least one integral tooth;   at least one non-integral tooth bonded to the surface of the roller cone adjacent to the at least one integral tooth, the at least one non-integral tooth comprising a particle-matrix composite material.   
     
     
         26 . The earth-boring bit of  claim 25 , wherein the at least one non-integral tooth comprises an interior region having a first hardfacing composition and an exterior region having a second hardfacing composition, the first hardfacing composition exhibiting a toughness greater than a toughness exhibited by the second hardfacing composition, and the second hardfacing composition exhibiting a wear resistance greater than a wear resistance exhibited by the first hardfacing composition. 
     
     
         27 . The earth-boring bit of  claim 25 , wherein the at least one non-integral tooth comprises multiple layers of hardfacing material.