An earth-boring tool includes a cutting element having a first volume of polycrystalline material including catalyst material and a second volume free of catalyst material. A boundary between the first volume and the second volume is nonlinear in a cross-sectional plane that includes a centerline of the cutting element and an anticipated point of contact of the cutting element with the surface of the formation to be cut. Each line tangent the boundary in the cross-sectional plane forms an angle with the centerline of the cutting element greater than the contact back rake angle of the cutting element. In some cutting elements, some portions of the boundary may have another selected shape. Some cutting elements have a boundary wherein tangent lines form angles of greater than 20 with the centerline of the cutting element. Methods of forming wellbores are also disclosed.

A polycrystalline element includes a table formed of polycrystalline diamond. The table includes a first surface; a second surface spaced apart from the first surface; and at least one side extending between the first surface and the second surface. The table also includes a plurality of extensions also formed of polycrystalline diamond, wherein at least one extension of the plurality of extensions extends away from at least one of the first surface and the at least one side. The at least one extension of the plurality of extensions includes a first portion that is polyhedral shaped. Optionally, the polycrystalline diamond of at least one extension of the plurality of extensions is contiguous with the polycrystalline diamond of the table. The polycrystalline element may be used in downhole tools for boring and well drilling, machine tools, and bearings.

A cutting element may include a substrate having a base. A cutting element may include an ultrahard layer bonded to the substrate, the ultrahard layer formed from an ultrahard material, the ultrahard layer including: a side surface adjacent to the base, the side surface including a plurality of cutting surfaces; and an upper surface extending into the ultrahard layer.

Methods of laser cutting polycrystalline diamond tables and polycrystalline diamond compacts are disclosed. Laser cutting of the polycrystalline diamond table provides an alternative to electrical-discharge machining (EDM), grinding with a diamond wheel, or lapping with a diamond wheel. Grinding or lapping with a diamond wheel is relatively slow and expensive, as diamond is used to remove a diamond material. EDM cutting of the polycrystalline diamond table is sometimes impractical or even impossible, particularly when the cobalt or other infiltrant or catalyst concentration within the polycrystalline diamond table is very low (e.g., in the case of a leached polycrystalline diamond table). As such, laser cutting provides a valuable alternative machining method that may be employed in various processes such as laser scribing, laser ablation, and laser lapping.

A cutting element for an earth-boring tool includes at least one volume of superabrasive material on a substrate. The volume of superabrasive material includes a first planar surface and a second planar surface oriented at an angle relative to the first planar surface and intersecting the first planar surface along an apex. The first planar surface has a circular or oval shape having a first maximum diameter, and the second planar surface has a circular or oval shape having a second maximum diameter. The apex has a length less than the first maximum diameter and the second maximum diameter. Earth-boring tools include such a cutting element attached to a body. Methods of forming earth-boring tools include the attachment of such a cutting element to a body of an earth-boring tool.

A cutter assembly includes a substrate and at least one island. The substrate includes a surface circumscribed by a peripheral edge, a flank surface extending from the peripheral edge, and at least one pocket with an opening on the surface and spaced apart from the peripheral edge. The at least one pocket extends from the opening towards an interior of the substrate. The at least one island is in the at least one pocket, and the at least one island includes a cutting surface that is exposed by the opening of the at least one pocket.

A polycrystalline element includes a table formed of polycrystalline diamond. The table includes a first surface; a second surface spaced apart from the first surface; and at least one side extending between the first surface and the second surface. The table also includes a plurality of extensions also formed of polycrystalline diamond, wherein at least one extension of the plurality of extensions extends away from at least one of the first surface and the at least one side. A radial line extends radially outward from a center axis of the first surface intersects each of a long axis of a subset of a plurality of extensions. Optionally, the polycrystalline diamond of at least one extension of the plurality of extensions is contiguous with the polycrystalline diamond of the table. The polycrystalline element may be used in downhole tools for boring and well drilling, machine tools, and bearings.

A cutting element includes a substrate configured to couple to a pocket formed in a blade of a downhole drill bit and a polycrystalline diamond portion secured to the substrate. The polycrystalline diamond portion includes a cutting face, a radial sidewall, and a cutting edge formed at a transition from the radial sidewall to the axial the cutting face. The cutting face includes a plow feature disposed at a center of the cutting face. The plow feature has a face portion and a shoulder portion. The shoulder portion extends radially outward from the face portion and axially downward toward the substrate. Additionally, the cutting face includes a recessed portion extending between the cutting edge and a radially outer edge of the shoulder portion.

A cutter element for a drill bit, comprising: a substrate having a longitudinal axis; a first layer of polycrystalline diamond coupled to the substrate; and a second layer of polycrystalline diamond coupled to the first layer at a first coherent boundary; where the first layer is axially positioned between the substrate and the second layer.

Methods of forming polycrystalline compacts include subjecting a plurality of grains of hard material interspersed with a catalyst material to high-temperature and high-pressure conditions to form a polycrystalline material having intergranular bonds and interstitial spaces between adjacent grains of the hard material. The catalyst material is disposed in at least some of the interstitial spaces in the polycrystalline material. The methods further comprise substantially removing the catalyst material from the interstitial spaces in at least a portion of the polycrystalline material to form an at least partially leached polycrystalline compact; and removing a portion of the polycrystalline material from which the catalyst material has been substantially removed from the at least partially leached polycrystalline compact. The polycrystalline cutting elements may be secured to a bit body of an earth-boring tool.