Methods of forming polycrystalline compacts having material disposed in interstitial spaces therein, cutting elements and earth-boring tools including such compacts

A method of forming a polycrystalline compact, comprising:

• preparing a first plurality of particles of hard material having a first average particle size and at least a second plurality of particles of hard material having a second average particle size larger than the first average particle size of the first plurality of particles of hard material for a subsequent sintering process, comprising:
• selecting a coating material for the first plurality of particles of hard material, the coating material comprising at least one of a boride, a carbide, a nitride, a metal carbonate, a metal bicarbonate, and a non-catalytic metal;
• at least partially coating each particle of the first plurality of particles of hard material with the coating material forming a first plurality of coated particles of hard material;
• and
• dispersing the first plurality of coated particles of hard material among the at least a second plurality of particles of hard material;
• sintering the first plurality of coated particles of hard material and the at least a second plurality of particles of hard material to form a polycrystalline hard material comprising a first plurality of hard material grains formed from the first plurality of coated particles of hard material and a second plurality of hard material grains formed from the at least a second plurality of particles of hard material, the first plurality of hard material grains and the second plurality of hard material grains being interspersed and interbonded to form the polycrystalline hard material, the coating material forming an interstitial material disposed in at least some interstitial spaces between the first plurality of hard material grains and the second plurality of hard material grains formed from the first plurality of particles of hard material and the second plurality of particles of hard material;
• and
• selecting the first average particle size of the first plurality of particles of hard material and the second average particle size of the at least a second plurality of particles of hard material to cause the second plurality of hard material grains to have a second average grain size at least about one hundred fifty (150) times larger than a first average grain size of the first plurality of hard material grains.

A method of forming an earth-boring tool having at least one cutting element, wherein the at least one cutting element includes a polycrystalline compact, comprising:

• preparing a plurality of nanoparticles of hard material for a subsequent sintering process, comprising:
• selecting a coating material comprising at least one of a boride, a carbide, a nitride, a metal carbonate, a metal bicarbonate, and a non-catalytic metal;
• and
• at least partially coating each nanoparticle of the plurality of nanoparticles of hard material with the coating material forming a plurality of coated nanoparticles of hard material;
• sintering the plurality of coated nanoparticles of hard material to form a polycrystalline hard material comprising a plurality of hard particle grains formed from the plurality of coated nanoparticles of hard material, the plurality of hard particle grains being interspersed and interbonded to form the polycrystalline hard material, the coating material forming an interstitial material disposed in at least some interstitial spaces between the plurality of hard material grains formed from the plurality of coated nanoparticles of hard material;
• forming a polycrystalline compact from the polycrystalline hard material;
• disposing the polycrystalline compact on a substrate to form the at least one cutting element;
• and
• joining the at least one cutting element to the earth-boring tool.