Methods of forming a polycrystalline diamond compact for use in an earth-boring tool include forming a body of polycrystalline diamond material including a first material disposed in interstitial spaces between inter-bonded diamond crystals in the body, removing the first material from interstitial spaces in a portion of the body, selecting a second material promoting a higher rate of degradation of the polycrystalline diamond compact than the first material under similar elevated temperature conditions and providing the second material in interstitial spaces in the portion of the body. Methods of drilling include engaging at least one cutter with a formation and wearing a second region of polycrystalline diamond material comprising a second material faster than the first region of polycrystalline diamond material comprising a first material. Polycrystalline diamond compacts and earth-boring tools including such compacts.

A method comprises rotating a drill bit of a drilling system at at least 1000 rpm. The drill system can comprise a drill feed, a drill head comprising a motor and coupled to the drill feed, a drill string, comprising at least one drill rod, operatively coupled to the drill head so that the drill head is configured to axially and rotationally drive the drill string, and the drill bit coupled to the bottom end of the drill string.

A cutting element for an earth-boring tool includes a substrate and a polycrystalline, superabrasive material secured to an end of the substrate. The polycrystalline, superabrasive material includes a curved, stress-reduction feature located at least on the first transition surface. The cutting element includes at least one recess defined in the curved, stress-reduction feature of the polycrystalline, superabrasive material. The at least one recess includes sidewalls intersecting with a front surface of the stress-reduction feature of the polycrystalline, superabrasive material and extending to a base wall within the polycrystalline, superabrasive material. The curved, stress-reduction feature includes an undulating edge formed proximate a peripheral edge of the polycrystalline, superabrasive material and a waveform extending from the undulating edge toward the center longitudinal axis of the cutting element.

A cutting element for an earth-boring tool includes a substrate and a polycrystalline, superabrasive material secured to an end of the substrate. The polycrystalline, superabrasive material includes a curved, stress-reduction feature located at least on the first transition surface. The cutting element includes at least one recess defined in the curved, stress-reduction feature of the polycrystalline, superabrasive material. The at least one recess includes sidewalls intersecting with a front surface of the stress-reduction feature of the polycrystalline, superabrasive material and extending to a base wall within the polycrystalline, superabrasive material. The curved, stress-reduction feature includes an undulating edge formed proximate a peripheral edge of the polycrystalline, superabrasive material and a waveform extending from the undulating edge toward the center longitudinal axis of the cutting element.

Methods of forming an earth-boring tool may involve attaching one or more cutting elements to a replaceable cutting structure and positioning the replaceable cutting structure proximate a region of a body of an earth-boring tool that is susceptible to at least one of localized wear and localized impact damage. The replaceable cutting structure may be secured to the body. Methods of repairing an earth-boring tool may involve bringing a replaceable cutting structure proximate at least one portion of a body of an earth-boring tool exhibiting at least one of localized wear and localized impact damage. The replaceable cutting structure may be attached to the earth-boring tool at the at least one portion.

Methods of forming an earth-boring tool may involve attaching one or more cutting elements to a replaceable cutting structure and positioning the replaceable cutting structure proximate a region of a body of an earth-boring tool that is susceptible to at least one of localized wear and localized impact damage. The replaceable cutting structure may be to the body. Methods of repairing an earth-boring tool may involve bringing a replaceable cutting structure proximate at least one portion of a body of an earth-boring tool exhibiting at least one of localized wear and localized impact damage. The replaceable cutting structure may be attached to the earth-boring tool at the at least one portion.