A superabrasive element includes at least one superabrasive table including at least one coupling projection having a narrow portion and a wide portion having a greater width than the narrow portion. The superabrasive element includes a substrate defining at least one coupling recess, the at least one coupling recess extending from a narrow portion to a wide portion. At least a portion of the at least one coupling projection is disposed in the coupling recess and the at least one coupling projection and the at least one coupling recess mechanically couple the at least one superabrasive table to the substrate. A drill bit includes a superabrasive element having a superabrasive table.

Polycrystalline elements include a substrate and a polycrystalline table attached to an end of the substrate. The polycrystalline table includes a first region of superabrasive material having a first permeability and at least a second region of superabrasive material having a second, lesser permeability, the at least a second region being interposed between the substrate and the first region. Methods of forming a polycrystalline element involve attaching a polycrystalline table including a first region of superabrasive material having a first permeability and at least a second region of superabrasive material having a second, lesser permeability to an end of a substrate, the at least a second region being interposed between the first region and the substrate. Catalyst material is removed from at least the first region of the polycrystalline table.

Cutting elements include polycrystalline diamond which may be attached to a substrate. The polycrystalline diamond may have a ratio of cubic to hexagonal cobalt crystalline structures of greater than about 1.2. The polycrystalline diamond may have a high level surface compressive stress of greater than about 500 MPa.

A cutting element for an earth-boring tool includes a volume of superabrasive material having a cutting face and a shaped feature on the cutting face. The shaped feature may include at least one of a recess extending into the volume of superabrasive material from the cutting face and a protrusion extending outward from the cutting face. A first portion of the cutting face may have a first surface roughness, and a second portion of the cutting face may have a second surface roughness greater than the first surface roughness of the first portion of the cutting face. The volume of superabrasive material may be disposed on a substrate. Methods of forming cutting elements may include forming one or more shaped features in a cutting face of the cutting elements. Earth-boring tools may include such cutting elements.

A method of forming a cutting element may include subjecting a first press containing at least a diamond powder-containing container and a volume of a high melting temperature non-reactive material to a first high pressure high temperature sintering condition to form a sintered polycrystalline diamond wafer including a diamond matrix of diamond grains bonded together and a plurality of interstitial spaces between the bonded together diamond grains; and subjecting a second press containing the sintered polycrystalline diamond wafer and a substrate to a second high temperature high pressure condition, thereby attaching the wafer to the substrate to form a cutting element having a polycrystalline diamond layer on the substrate.

A polycrystalline diamond compact (PDC) is fabricated using a process of delayed diffusion (i.e., post-sintering) of a diffusion species (i.e., a metalloid) introduced from the back side of a carbide further away from the diamond grit or from the flank side of the carbide, as opposed to the side of the carbide adjacent to the diamond grit. The process of fabricating the PDC includes depositing, in a metal container, a synthetic diamond grit, a carbide, and a diffusion species, then applying a high pressure and high temperature (HPHT) to the contents of the metal container wherein (1) the carbide diffuses across the diamond grit, and (2) the diffusion species diffuses across the carbide followed by the diamond grit, thus providing a protective coating to the PDC.

A polycrystalline diamond compact (PDC) is fabricated using a process of delayed diffusion (i.e., post-sintering) of a diffusion species (i.e., a metalloid) introduced from the back side of a carbide further away from the diamond grit or from the flank side of the carbide, as opposed to the side of the carbide adjacent to the diamond grit. The process of fabricating the PDC includes depositing, in a metal container, a synthetic diamond grit, a carbide, and a diffusion species, then applying a high pressure and high temperature (HPHT) to the contents of the metal container wherein (1) the carbide diffuses across the diamond grit, and (2) the diffusion species diffuses across the carbide followed by the diamond grit, thus providing a protective coating to the PDC.

A cutting element comprises a supporting substrate, and a polycrystalline compact attached to an end of the supporting substrate. The polycrystalline compact comprises a region adjacent the end of the supporting substrate, and another region at least substantially laterally circumscribing the region and having lesser permeability than the region. A method of forming a cutting element, and an earth-boring tool are also described.

A method of forming polycrystalline diamond includes encapsulating diamond particles, carbon monoxide, and carbon dioxide in a container. The encapsulated diamond particles, carbon monoxide, and carbon dioxide are subjected to a pressure of at least 4.5 GPa and a temperature of at least 1,400 C. to form inter-granular bonds between the diamond particles. A cutting element includes polycrystalline diamond material comprising inter-bonded grains of diamond. The polycrystalline diamond material is substantially free of graphitic carbon and metallic compounds. The polycrystalline diamond material exhibits a density of at least about 3.49 g/cm.sup.3 and a modulus of at least about 1,000 GPa. An earth-boring tool may include such a cutting element secured to a body.

Various shaped abrasive particles are disclosed. Each shaped abrasive particle includes a body having at least one major surface and a side surface extending from the major surface.