Method of making cutter elements

Abstract

A method for making a cutter element, the method including combining a plurality of super-hard grains, a powder source of bond material for bonding the super-hard grains in the cutter element, and a fluid medium to form a paste, in which the content of the super-hard grains is sufficient for the content of the super-hard grains in the cutter element to be at least about 3 volume percent. The paste is introduced into an extrusion device and extruded to form a green body, which is sintered to provide the cutter element. In some examples, the cutter element may be for a saw blade or drill bit.

1 . A method for making a cutter element, the method including combining a plurality of super-hard grains falling within the 12/200 U.S. mesh band, a powder source of bond material for bonding the super-hard grains in the cutter element, and a fluid medium to form a paste; introducing the paste into an extrusion device, extruding the paste to form a green body and sintering the green body to provide the cutter element; in which the content of the super-hard grains in the paste is sufficient for the content of the super-hard grains in the cutter element to be 3 to 60 volume percent. 
     
     
         2 . A method as claimed in  claim 1 , in which the super-hard grains diamond or cubic boron nitride (cBN). 
     
     
         3 . A method as claimed in  claim 1 , in which the bond material comprises cobalt. 
     
     
         4 . A method as claimed in  claim 1 , including combining particulate metal carbide material with the super-hard grains, the bond material and the fluid medium. 
     
     
         5 . A method as claimed in  claim 4 , in which the weight ratio of the bond material and the metal carbide material is at least 10:90 and at most 90:10. 
     
     
         6 . A method as claimed in  claim 1 , including combining fluid thickening material with the super-hard grains, the bond material and the fluid medium, operative to increase the viscosity of the fluid. 
     
     
         7 . A method as claimed in  claim 1 , including treating the paste mechanically or aging the paste to increase the viscosity of the paste. 
     
     
         8 . A method as claimed in  claim 1 , including introducing the paste into a mould chamber and pressurising the paste. 
     
     
         9 . A method as claimed in  claim 1 , including extruding the paste to form an intermediate body, introducing the intermediate body into the extrusion device and pressurising the intermediate body to extrude the paste comprised in the intermediate body. 
     
     
         10 . A method as claimed in  claim 1 , including at least three extrusion cycles, each extrusion cycle including extruding the paste. 
     
     
         11 . A method as claimed in  claim 1 , including forming the paste into an intermediate body and processing the intermediate body into at least one green body. 
     
     
         12 . A method as claimed in  claim 11 , in which processing the intermediate body includes cutting it. 
     
     
         13 . A method as claimed in  claim 1 , in which the density of the green body is at least 40 percent and at most 70 percent of the maximum combined theoretical density of the constituent materials apart from the fluid medium. 
     
     
         14 . A method as claimed in  claim 1 , in which at least part of the green body is cylindrical or rhombohedral in shape. 
     
     
         15 . A method as claimed in any of the preceding claims  claim 1 , including subjecting the green body to an elevated temperature and pressure to form the cutter element. 
     
     
         16 . A method as claimed in  claim 1 , including providing a second paste comprising powder capable of being sintered to form a part of a cutter element, the second paste having a different material composition from the paste, combining the past with the second paste to form a green body and sintering the green body to form a cutter element. 
     
     
         17 . A method as claimed in  claim 16 , in which the second paste comprises super-hard grains having a different size distribution from the super-hard grains in the paste. 
     
     
         18 . A method as claimed in  claim 16 , in which the second paste comprises a different content of super-hard grains than the first paste. 
     
     
         19 . A method as claimed in  claim 16 , in which the second paste is free of super-hard grains. 
     
     
         20 . A method as claimed in  claim 1 , in which at least some of the super-hard grains are provided encapsulated within pellets. 
     
     
         21 . A method as claimed in  claim 20 , in which the volume of each pellet is at least double the volume of the super-hard grain. 
     
     
         22 . A method as claimed in  claim 20 , in which each pellet comprises a super-hard grain, an inner encapsulation zone at least partially enclosing the super-hard grain and an outer encapsulation zone at least partially enclosing the inner encapsulation zone; the inner encapsulation zone being substantially more resistant to abrasive wear than the outer encapsulation zone. 
     
     
         23 . A method as claimed in  claim 22 , in which the volume of the inner encapsulation zone is at least  20  percent of the volume of the pellet. 
     
     
         24 . A method as claimed in  claim 1 , in which the cutter element is for a drill bit for boring into the earth. 
     
     
         25 . A method as claimed in  claim 1 , in which the cutter element is for a saw blade.