Methods of forming polycrystalline diamond compacts and earth-boring tools

1. A method of forming a polycrystalline diamond compact, the method comprising:

providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto, the sweep catalyst comprising at least one of tungsten and tungsten carbide and constituting between about 0.01 weight percent and about 1.0 weight percent of the metallized diamond particles;

placing the metallized diamond particles and a metal solvent catalyst in a container; and

subjecting the metallized diamond particles to a high-temperature, high-pressure process in the presence of the metal solvent catalyst to form a polycrystalline diamond material having inter-bonded diamond grains and nanograins of tungsten carbide, the nanograins of tungsten carbide covering less than about twenty percent of a surface area of the inter-bonded diamond grains.

2. The method of claim 1 , wherein placing the metallized diamond particles and a metal solvent catalyst in a container further comprises placing the metallized diamond particles adjacent to a substrate in a container, the substrate including the metal solvent catalyst, the method further comprising enhancing, by the presence of the sweep catalyst secured to the diamond particles, a rate of sweep of the metal solvent catalyst through and between the diamond particles while subjecting the metallized diamond particles to the high-temperature, high-pressure process in the presence of the metal solvent catalyst.

3. The method of claim 1 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises providing diamond particles including discrete grains of at least one of tungsten and tungsten carbide having an average grain size of between about 0.2 nm and about 500 nm secured thereto.

4. The method of claim 1 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises forming the sweep catalyst on surfaces of the diamond particles by chemical vapor deposition.

5. The method of claim 4 , wherein forming the sweep catalyst on surfaces of the diamond particles by chemical vapor deposition comprises exposing the diamond particles to at least one of tungsten hexafluoride, tungsten hexachloride, and tungsten (hexa)carbonyl.

6. The method of claim 1 , further comprising selecting the metal solvent catalyst to comprise cobalt.

7. The method of claim 1 , further comprising selecting the metallized diamond particles to consist essentially of the diamond particles and tungsten carbide.

8. The method of claim 1 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises providing diamond particles having about one monolayer of tungsten or tungsten carbide thereon.

9. The method of claim 1 , wherein subjecting the metallized diamond particles to a high-temperature, high-pressure process in the presence of the metal solvent catalyst to form a polycrystalline diamond material comprises forming the polycrystalline diamond material to have tungsten carbide covering less than about five percent of the surface area of the inter-bonded diamond grains.

10. The method of claim 1 , wherein subjecting the metallized diamond particles to a high-temperature, high-pressure process in the presence of the metal solvent catalyst to form a polycrystalline diamond material comprises forming the polycrystalline diamond material to have tungsten carbide covering less than about one percent of the surface area of the inter-bonded diamond grains.

11. The method of claim 1 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises providing diamond particles coated with nanograins consisting essentially of tungsten carbide.

12. The method of claim 1 , further comprising leaching the polycrystalline diamond material to remove at least a portion of the metal solvent catalyst and the sweep catalyst from at least a portion of the polycrystalline diamond material.

13. A method of forming an earth-boring tool, the method comprising:

providing a bit body; and

forming at least one polycrystalline diamond compact cutting element, wherein forming at least one polycrystalline diamond compact cutting element comprises:

providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto, the sweep catalyst comprising at least one of tungsten and tungsten carbide and constituting between about 0.01 weight percent and about 1.0 weight percent of the metallized diamond particles;

placing the metallized diamond particles and a metal solvent catalyst in a container; and subjecting the metallized diamond particles to a high-temperature, high-pressure process in the presence of the metal solvent catalyst to form a polycrystalline diamond material having inter-bonded diamond grains and nanograins of tungsten carbide, the nanograins of tungsten carbide covering less than about twenty percent of a surface area of the inter-bonded diamond grains; and

securing the at least one polycrystalline diamond compact cutting element to the bit body.

14. The method of claim 13 , wherein placing the metallized diamond particles and a metal solvent catalyst in a container further comprises placing the metallized diamond particles adjacent to a substrate in a container, the substrate including the metal solvent catalyst, the method further comprising enhancing, by the presence of the sweep catalyst secured to the diamond particles, a rate of sweep of the metal solvent catalyst through and between the diamond particles while subjecting the metallized diamond particles to the high-temperature, high-pressure process in the presence of the metal solvent catalyst.

15. The method of claim 13 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises providing diamond particles including discrete grains of at least one of tungsten and tungsten carbide having an average grain size of between about 0.2 nm and about 500 nm secured thereto.

16. The method of claim 13 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises forming the sweep catalyst on surfaces of the diamond particles by chemical vapor deposition.

17. The method of claim 16 , wherein forming the sweep catalyst on surfaces of the diamond particles by chemical vapor deposition comprises exposing the diamond particles to at least one of tungsten hexafluoride, tungsten hexachloride, and tungsten (hexa)carbonyl.

18. The method of claim 13 , further comprising selecting the metal solvent catalyst to comprise cobalt.

19. The method of claim 13 , further comprising selecting the metallized diamond particles to consist essentially of the diamond particles and tungsten carbide.

20. The method of claim 13 , wherein providing metallized diamond particles comprising diamond particles including nanograins of a sweep catalyst secured thereto comprises providing diamond particles having about one monolayer of tungsten or tungsten carbide thereon.