Abstract: Polycrystalline compacts include an interface between first and second volumes of a body of inter-bonded grains of hard material. The first volume is at least substantially free of interstitial material, and the second volume includes interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material. The interface between the first and second volumes is configured, located and oriented such that cracks originating in the compact during use of the compacts and propagating along the interface generally toward a central axis of the compacts will propagate generally toward a back surface and away from a front cutting face of the compacts at an acute angle or angles. Methods of forming polycrystalline compacts involve the formation of such an interface within the compacts.

Abstract: A method of forming an earth-boring tool includes introducing metal into a die, rotating the die to generate centrifugal forces on the metal, and cooling the metal in the rotating die. A rotary drill bit may include a unitary, centrifugally cast bit body including an integral shank, at least one blade, and at least one cutting element on the blade. A rotary drill bit or a roller cone may include a first centrifugally cast material and a second centrifugally cast material. Another rotary drill bit includes a bit body comprising a maraging steel alloy. A method of forming a rotary drill bit may include disposing cutting elements on a rotary drill bit comprising maraging steel and aging the rotary drill bit to form at least one intermetallic precipitate phase. Methods of repairing a rotary drill bit include annealing and aging at least a portion of a rotary drill bit.

Abstract: Polycrystalline compacts include an interface between first and second volumes of a body of inter-bonded grains of hard material. The first volume is at least substantially free of interstitial material, and the second volume includes interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material. The interface between the first and second volumes is configured, located and oriented such that cracks originating in the compact during use of the compacts and propagating along the interface generally toward a central axis of the compacts will propagate generally toward a back surface and away from a front cutting face of the compacts at an acute angle or angles. Methods of forming polycrystalline compacts involve the formation of such an interface within the compacts.

Abstract: Polycrystalline compacts include an interface between first and second volumes of a body of inter-bonded grains of hard material. The first volume is at least substantially free of interstitial material, and the second volume includes interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material. The interface between the first and second volumes is configured, located and oriented such that cracks originating in the compact during use of the compacts and propagating along the interface generally toward a central axis of the compacts will propagate generally toward a back surface and away from a front cutting face of the compacts at an acute angle or angles. Methods of forming polycrystalline compacts involve the formation of such an interface within the compacts.

Abstract: A cutting element for an earth-boring tool includes an elongated body having a longitudinal axis, a generally planar volume of hard material attached to the elongated body, and a sensor affixed to the elongated body. The sensor may be configured to sense at least one of stress and strain. An earth-boring tool includes a cutting element disposed at least partially within a pocket of a body. Methods of forming cutting elements comprise securing a generally planar volume of hard material to an elongated body, attaching a sensor to the elongated body, and configuring the sensor. Methods of forming earth-boring tools comprise forming a cutting element and securing the cutting element within a recess in a body of the earth-boring tool. Methods of forming wellbores comprise rotating an earth-boring tool comprising a cutting element and measuring at least one of stress and strain.

Abstract: A method of forming an earth-boring tool includes introducing metal into a die, rotating the die to generate centrifugal forces on the metal, and cooling the metal in the rotating die. A rotary drill bit may include a unitary, centrifugally cast bit body including an integral shank, at least one blade, and at least one cutting element on the blade. A rotary drill bit or a roller cone may include a first centrifugally cast material and a second centrifugally cast material. Another rotary drill bit includes a bit body comprising a maraging steel alloy. A method of forming a rotary drill bit may include disposing cutting elements on a rotary drill bit comprising maraging steel and aging the rotary drill bit to form at least one intermetallic precipitate phase. Methods of repairing a rotary drill bit include annealing and aging at least a portion of a rotary drill bit.

Abstract: A method of forming an earth-boring tool includes introducing metal into a die, rotating the die to generate centrifugal forces on the metal, and cooling the metal in the rotating die. A rotary drill bit may include a unitary, centrifugally cast bit body including an integral shank, at least one blade, and at least one cutting element on the blade. A rotary drill bit or a roller cone may include a first centrifugally cast material and a second centrifugally cast material. Another rotary drill bit includes a bit body comprising a maraging steel alloy. A method of forming a rotary drill bit may include disposing cutting elements on a rotary drill bit comprising maraging steel and aging the rotary drill bit to form at least one intermetallic precipitate phase. Methods of repairing a rotary drill bit include annealing and aging at least a portion of a rotary drill bit.

Abstract: Polycrystalline compacts include an interface between first and second volumes of a body of inter-bonded grains of hard material. The first volume is at least substantially free of interstitial material, and the second volume includes interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material. The interface between the first and second volumes is configured, located and oriented such that cracks originating in the compact during use of the compacts and propagating along the interface generally toward a central axis of the compacts will propagate generally toward a back surface and away from a front cutting face of the compacts at an acute angle or angles. Methods of forming polycrystalline compacts involve the formation of such an interface within the compacts.

Abstract: Methods of attaching cutting elements to earth-boring tools, comprising abutting a portion of a cutting element against at least one surface of an earth-boring tool with a braze material disposed therebetween; and brazing the cutting element to the earth-boring tool by applying high-frequency vibrations to cause the braze material to become flowable. Methods of securing cutting elements to earth-boring tools may comprise at least partially coating a cutting element with a braze material. The cutting element may be at least partially disposed in a pocket formed in a body of an earth-boring tool with the braze material adjacent surfaces defining the pocket. The cutting element and the braze material may be ultrasonically torsionally oscillated to braze the cutting element within the pocket.

Abstract: A method of forming an earth-boring tool includes introducing metal into a die, rotating the die to generate centrifugal forces on the metal, and cooling the metal in the rotating die. A rotary drill bit may include a unitary, centrifugally cast bit body including an integral shank, at least one blade, and at least one cutting element on the blade. A rotary drill bit or a roller cone may include a first centrifugally cast material and a second centrifugally cast material. Another rotary drill bit includes a bit body comprising a maraging steel alloy. A method of forming a rotary drill bit may include disposing cutting elements on a rotary drill bit comprising maraging steel and aging the rotary drill bit to form at least one intermetallic precipitate phase. Methods of repairing a rotary drill bit include annealing and aging at least a portion of a rotary drill bit.

Abstract: Methods of attaching cutting elements to earth-boring tools, comprising abutting a portion a cutting element against at least one surface of an earth-boring tool with a braze material disposed therebetween; and brazing the cutting element to the earth-boring tool by applying high-frequency vibrations to cause the braze material to become flowable. Methods of securing cutting elements to earth-boring tools may comprise at least partially coating a cutting element with a braze material. The cutting element may be at least partially disposed in a pocket formed in a body of an earth-boring tool with the braze material adjacent surfaces defining the pocket. The cutting element and the braze material may be ultrasonically torsionally oscillated to braze the cutting element within the pocket.

Abstract: A cutting element for an earth-boring tool includes an elongated body having a longitudinal axis, a generally planar volume of hard material attached to the elongated body, and a sensor affixed to the elongated body. The sensor may be configured to sense at least one of stress and strain. An earth-boring tool includes a cutting element disposed at least partially within a pocket of a body. Methods of forming cutting elements comprise securing a generally planar volume of hard material to an elongated body, attaching a sensor to the elongated body, and configuring the sensor. Methods of forming earth-boring tools comprise forming a cutting element and securing the cutting element within a recess in a body of the earth-boring tool. Methods of forming wellbores comprise rotating an earth-boring tool comprising a cutting element and measuring at least one of stress and strain.