Methods of forming at least a portion of earth-boring tools, and articles formed by such methods

1. A method of forming at least a portion of an earth-boring tool, comprising:

providing particulate matter comprising a hard material in a mold cavity;

melting a metal and the hard material to form a molten composition comprising a eutectic or near-eutectic composition of the metal and the hard material;

casting the molten composition to form the at least a portion of an earth-boring tool within the mold cavity; and

providing an inoculant within the mold cavity.

2. The method of claim 1 , further comprising adjusting a stoichiometry of at least one hard material phase of the at least a portion of the earth-boring tool.

3. The method of claim 2 , wherein adjusting a stoichiometry of at least one hard material phase of the at least a portion of the earth-boring tool comprises converting at least one of an M 6 C phase and an M 12 C phase to at least one of an MC phase and an M 2 C phase, wherein M is at least one metal element and C is carbon.

4. The method of claim 3 , wherein converting at least one of an M 6 C phase and an M 12 C phase to at least one of an MC phase and an M 2 C phase comprises converting W x Co y C to WC, wherein x is from about 0.5 to about 6 and y is from about 0.5 to about 6.

5. The method of claim 1 , wherein melting a metal and a hard material to form a molten composition comprises melting a mixture comprising from about 40% to about 90% cobalt or cobalt-based alloy by weight and from about 0.5% to about 3.8% carbon by weight, wherein a balance of the mixture is at least substantially comprised of tungsten.

6. The method of claim 1 , wherein melting a metal and a hard material to form a molten composition comprises melting a mixture comprising from about 55% to about 85% cobalt or cobalt-based alloy by weight and from about 0.85% to about 3.0% carbon by weight, wherein a balance of the mixture is at least substantially comprised of tungsten.

7. The method of claim 1 , wherein melting a metal and a hard material to form a molten composition comprises melting a mixture comprising from about 65% to about 78% cobalt or cobalt-based alloy by weight and from about 1.3% to about 2.35% carbon by weight, wherein a balance of the mixture is at least substantially comprised of tungsten.

8. The method of claim 1 , wherein melting a metal and a hard material to form a molten composition comprises melting a mixture comprising about 69% cobalt or cobalt-based alloy by weight, about 1.9% carbon by weight, and about 29.1% tungsten by weight.

9. The method of claim 1 , wherein melting a metal and a hard material to form a molten composition comprises melting about 75% cobalt or cobalt-based alloy by weight, about 1.53% carbon by weight, and about 23.47% tungsten by weight.

10. The method of claim 1 , wherein providing the inoculant comprises providing at least one of a transition metal aluminate, a transition metal metasilicate, and a transition metal oxide.

11. The method of claim 1 , wherein providing the inoculant comprises providing at least one of cobalt aluminate, cobalt metasilicate, and cobalt oxide.

12. The method of claim 1 , wherein melting a metal and a hard material to form a molten composition comprises forming a eutectic or near-eutectic composition of cobalt and tungsten carbide.

13. The method of claim 1 , wherein providing the inoculant comprises controlling grain growth as the molten composition solidifies.

14. A method of forming a roller cone of an earth-boring rotary drill bit, comprising:

forming a molten composition comprising a eutectic or near-eutectic composition of cobalt and tungsten carbide;

casting the molten composition within a mold cavity;

solidifying the molten composition within the mold cavity to form the roller cone; and

controlling grain growth using an inoculant as the molten composition solidifies within the mold cavity.

15. The method of claim 14 , further comprising converting at least one of a W 3 Co 3 C phase region and a W 6 Co 6 C phase region within the roller cone to at least one of WC and W 2 C.

16. The method of claim 14 , wherein forming a molten composition comprises forming a molten composition comprising about 69% cobalt or cobalt-based alloy by weight, about 1.9% carbon by weight, and about 29.1% tungsten by weight.

17. The method of claim 14 , wherein controlling grain growth comprises adding at least one of a transition metal aluminate, a transition metal metasilicate, and a transition metal oxide to the mold cavity.

18. The method of claim 14 , wherein controlling grain growth comprises adding at least one of cobalt aluminate, cobalt metasilicate, and cobalt oxide to the mold cavity.