Earth-boring tools comprising eutectic or near-eutectic compositions

Abstract

Articles comprising at least a portion of an earth-boring tool include at least one insert and a solidified eutectic or near-eutectic composition including a metal phase and a hard material phase. Other articles include a solidified eutectic or near-eutectic composition including a metal phase, a hard material phase and a coating material in contact with the solidified eutectic or near-eutectic composition.

1 . A method of forming at least a portion of an earth-boring tool, comprising:
 coating at least one surface of a mold cavity defined by a mold with a coating material having a composition differing from a composition of the mold;   melting a metal and a hard material to form a molten composition comprising a eutectic or near-eutectic composition of the metal and the hard material; and   casting the molten composition within the mold cavity.   
     
     
         2 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises coating the at least one surface of the mold cavity with a material substantially free of carbon. 
     
     
         3 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises coating the at least one surface of the mold cavity with a ceramic oxide material. 
     
     
         4 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises coating the at least one surface of the mold cavity with at least one of zirconium oxide, silicon oxide, aluminum oxide, and yttrium oxide. 
     
     
         5 . The method of  claim 1 , wherein coating at least one surface of a mold cavity with a coating material having a composition differing from a composition of the mold comprises coating the at least one surface of the mold cavity with a coating material at least substantially comprised of zirconium oxide. 
     
     
         6 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises:
 forming at least one layer of a multilayer coating having a first composition; and   forming at least another layer of the multilayer coating having a second composition differing from the first composition.   
     
     
         7 . The method of  claim 6 , wherein forming the at least one layer of the multilayer coating having the first composition comprises forming a barrier material between a portion of the mold and the at least another layer of the multilayer coating. 
     
     
         8 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises coating the at least one surface of a mold cavity with a material formulated to react with the molten composition within the mold cavity. 
     
     
         9 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises coating the at least one surface of a mold cavity with a material formulated to be incorporated as an additional phase into the at least a portion of an earth-boring tool within the mold cavity. 
     
     
         10 . The method of  claim 1 , wherein coating the at least one surface of the mold cavity with the coating material comprises:
 depositing particles of the coating material on the at least one surface of the mold cavity; and   heating the particles of the coating material while they are disposed on the at least one surface of the mold cavity.   
     
     
         11 . The method of  claim 10 , wherein heating the particles of the coating material while they are disposed on the at least one surface of the mold cavity comprises at least partially sintering the particles of the coating material. 
     
     
         12 . The method of  claim 1 , wherein coating at least one surface of a mold cavity comprises contacting a liquid carrying the coating material with the at least one surface of the mold cavity. 
     
     
         13 . The method of  claim 12 , further comprising drying the liquid to leave the coating material on the at least one surface. 
     
     
         14 . The method of  claim 1 , wherein the method comprises forming a roller cone. 
     
     
         15 . The method of  claim 1 , wherein melting a metal and a hard material to form a molten composition comprises forming the eutectic or near-eutectic composition to comprises an inoculant. 
     
     
         16 . The method of  claim 15 , wherein the inoculant comprises at least one material selected from the group consisting of cobalt aluminate, cobalt metasilicate, and cobalt oxide. 
     
     
         17 . The method of  claim 1 , wherein the eutectic or near-eutectic composition comprises tungsten carbide and a metal selected from the group consisting of cobalt and a cobalt-based alloy. 
     
     
         18 . The method of  claim 1 , further comprising solidifying the molten composition to form at least two segregated solid phases. 
     
     
         19 . The method of  claim 18 , wherein at least one phase of the at least two segregated phases comprises a phase having a formula selected from the group consisting of M 6 C and M 12 C, wherein M represents a metal and C represents carbon. 
     
     
         20 . The method of  claim 18 , wherein at least one phase of the at least two segregated phases comprises a phase having a formula W x Co y C, wherein W represents tungsten, Co represents cobalt, and C represents carbon, wherein x is from about 0.5 to about 6, and y is from about 0.5 to about 6.