Impregnated cutting structures, earth-boring tools including the impregnated cutting structures, and related methods
A method of forming an impregnated cutting structure for an earth-boring tool comprises providing a powder mixture comprising diamond particles and a metal binder in a press and subjecting the powder mixture to a pressure greater than about 4.0 GPa and a temperature greater than about 1,200° C. to densify the powder mixture and form an impregnated cutting structure comprising the diamond particles dispersed in a continuous phase comprising the metal binder, wherein the impregnated cutting structure is substantially free of diamond-to-diamond bonds and of carbides. Related methods of forming an earth-boring tool and a related earth-boring tool including the impregnated cutting structure.
1. A method of forming an impregnated cutting structure for an earth-boring tool, the method comprising:
providing a powder mixture comprising diamond particles and a metal binder in a press, the powder mixture free of carbides; and
subjecting the powder mixture to a pressure greater than about 6.0 GPa and a temperature greater than about 1,400° C. to densify the powder mixture and form an impregnated cutting structure comprising the diamond particles dispersed in a continuous phase comprising the metal binder, wherein the impregnated cutting structure is substantially free of diamond-to-diamond bonds and of carbides.
2. The method of claim 1 , further comprising subjecting the powder mixture in the press to a pressure between about 100 MPa and about 1,000 MPa to form a green body prior to subjecting the powder mixture to a pressure greater than about 4.0 GPa and a temperature greater than about 1,200° C.
3. The method of claim 2 , wherein subjecting the powder mixture in the press to a pressure between about 100 MPa and about 1,000 MPa to form a green body comprises subjecting the powder mixture to a pressure about 100 MPa and about 1,000 MPa at a temperature between about 20° C. and about 25° C.
4. The method of claim 2 , wherein providing a powder mixture comprising diamond particles and a metal binder in a press comprises providing a powder mixture substantially free of carbides in the press.
5. The method of claim 1 , wherein subjecting the powder mixture to a pressure greater than about 6.0 GPa and a temperature greater than about 1,400° C. comprises forming the impregnated cutting structure to have a density between about 10.7 g/cm 3 and about 10.9 g/cm 3 and a porosity between about 0.05% and about 3.0%.
6. The method of claim 1 , further comprising selecting the powder mixture to consist essentially of the diamond particles and the metal binder.
7. The method of claim 1 , further comprising selecting the diamond particles to constitute between about 40 volume percent and about 45 volume percent of the powder mixture.
8. The method of claim 7 , further comprising selecting the metal binder to constitute a remainder of the powder mixture.
9. The method of claim 1 , further comprising selecting the metal binder to consist essentially of iron and at least one of nickel and cobalt, the weight percent of the iron within the metal binder between about 20 weight percent and about 80 percent and the weight percent of the at least one of nickel and cobalt within the metal binder between about 20 weight percent and about 80 percent.
10. The method of claim 1 , further comprising selecting the metal binder to comprise at least one of manganese and vanadium.
11. The method of claim 1 , further comprising selecting the metal binder to have a melting point greater than about 1,300° C., wherein subjecting the powder mixture to a pressure greater than about 6.0 GPa and a temperature greater than about 1,400° C. comprises subjecting the powder mixture to a temperature less than the melting point of the metal binder.
12. The method of claim 1 , wherein subjecting the powder mixture to a pressure greater than about 4.0 GPa comprises subjecting the powder mixture to a pressure greater than about 6.5 GPa.
13. The method of claim 1 , wherein subjecting the powder mixture to a pressure greater than about 4.0 GPa and a temperature greater than about 1,200° C. to densify the powder mixture and form an impregnated cutting structure comprises forming an impregnated cutting structure comprising a substantially uniform distribution of the diamond particles in the continuous phase.
14. The method of claim 1 , further comprising selecting the diamond particles to comprise single-crystal diamond.
15. A method of forming an earth-boring tool including an impregnated cutting structure, the method comprising:
forming an impregnated cutting structure, comprising:
providing a powder mixture comprising diamond particles and a metal binder in a press, the diamond particles coated with a metal coating; and
subjecting the powder mixture to a pressure greater than about 4.0 GPa and a temperature greater than about 1,200° C. to densify the powder mixture and form an impregnated cutting structure comprising the diamond particles dispersed in the metal binder, wherein the impregnated cutting structure is substantially free of diamond-to-diamond bonds and carbides; and
attaching the impregnated cutting structure to a blade of an earth-boring tool.
16. The method of claim 15 , further comprising selecting the metal binder to consist essentially of iron and at least one of cobalt and nickel, the binder free of copper.
17. The method of claim 15 , wherein:
subjecting the powder mixture to a pressure greater than about 4.0 GPa and a temperature greater than about 1,200° C. comprises subjecting the powder mixture to a temperature greater than about 1,500° C.; and
providing a powder mixture comprising diamond particles and a metal binder in a press, the diamond particles coated with a metal coating comprises providing diamond particles coated with the same metal as the metal of the metal binder.
18. An earth-boring tool for drilling subterranean formations,
the earth-boring tool comprising:
a bit body;
at least one blade in a crown region of the bit body; and
at least one impregnated cutting structure attached to the at least one blade, the at least one impregnated cutting structure comprising diamond particles coated with a metal coating and dispersed substantially uniformly in a metal binder in at least one region of at least one impregnated cutting structure, the at least one impregnated cutting structure substantially free of diamond-to-diamond bonds and carbides, and formed by exposing a powder mixture comprising the diamond particles coated with the metal coating and the metal binder material to a pressure greater than about 4.0 GPa and a temperature greater than about 1,200° C.
19. The earth-boring tool of claim 18 , wherein the metal binder has a melting point greater than about 1,300° C.
20. The earth-boring tool of claim 18 , wherein;
the metal binder consists essentially of nickel and iron; and
the metal coating comprises a transition metal.