A carbide composite for a downhole tool may be formed by depositing a first layer on a substrate, and a second layer at least partially adjacent to the first layer. The first and second layers may each include carbides, metal binders, organic binders, or a combination thereof. The first and second carbide layers may have a different particle size, particle shape, carbide concentration, metal binder concentration, or organic binder concentration from one another.

A carbide composite for a downhole tool may be formed by depositing a first layer on a substrate, and a second layer at least partially adjacent to the first layer. The first and second layers may each include carbides, metal binders, organic binders, or a combination thereof. The first and second carbide layers may have a different particle size, particle shape, carbide concentration, metal binder concentration, or organic binder concentration from one another.

A percussive rock drill bit includes a plurality of peripheral gauge buttons distributed circumferentially around an axially forwardmost collar at the drill head. The gauge buttons are grouped into pairs such that the central axes of neighboring gauge buttons are aligned substantially parallel to one another and are not centered on a longitudinal axis of the bit. Enlarged flushing grooves are located at the annular collar to provide a segmented collar configuration optimized for flushing cut material rearwardly from the drill bit.

A percussive rock drill bit includes a plurality of peripheral gauge buttons distributed circumferentially around an axially forwardmost collar at the drill head. The gauge buttons are grouped into pairs such that the central axes of neighboring gauge buttons are aligned substantially parallel to one another and are not centered on a longitudinal axis of the bit. Enlarged flushing grooves are located at the annular collar to provide a segmented collar configuration optimized for flushing cut material rearwardly from the drill bit.

An earth-boring tool comprising a body having first cutting elements mounted to an axially leading face, the first cutting elements each having a cutting face exposed to a height above the face of the body, the cutting faces of the first cutting elements back raked and facing a direction of intended rotation of the earth-boring tool. The earth-bring tool further comprises second cutting elements mounted to the axially leading face of the body adjacent first cutting elements in a cone region of the bit face, the second cutting elements each having a cutting face exposed to a height above the face of the body and configured for a shear-type cutting action, the cutting faces of the second cutting elements back raked to about a same or greater extent than the first cutting elements and generally facing the direction of intended rotation of the earth-boring tool.

A method of modifying surfaces of diamond particles comprises forming spinodal alloy coatings over discrete diamond particles, thermally treating the spinodal alloy coatings to form modified coatings each independently exhibiting a reactive metal phase and a substantially non-reactive metal phase, and etching surfaces of the discrete diamond particles with at least one reactive metal of the reactive metal phase of the modified coatings. Diamond particles and earth-boring tools are also described.

A method of modifying surfaces of diamond particles comprises forming spinodal alloy coatings over discrete diamond particles, thermally treating the spinodal alloy coatings to form modified coatings each independently exhibiting a reactive metal phase and a substantially non-reactive metal phase, and etching surfaces of the discrete diamond particles with at least one reactive metal of the reactive metal phase of the modified coatings. Diamond particles and earth-boring tools are also described.

A cutting element for a drill bit is advanceable into a subterranean formation to form a wellbore. The cutting element includes an element body having a face at an end thereof, and a ridge. The element body has a face at an end thereof. The face has a ramp and a pair of side regions thereon. The ramp has a curved edge along a periphery of the face and two sides. Each of the two sides extends from opposite ends of the curved edge and converges at a location along the face. The face has a chamfer along a peripheral edge thereof. The ridge is between the chamfer and the location. Each of the pair of side regions is positioned on opposite sides of the ridge and extends between the periphery, the ridge, and one of the two sides of the ramp whereby the chamfer engages a wall of the wellbore and extrudate is drawn along the pair of side regions.

Wear sensors are provided on a drill bit or other rotary cutting tool which is for operation in a subterranean borehole and has a plurality of separate cutters protruding from a support structure towards the material to be cut by the tool. The electrically operated sensing means are located at or coupled to a sensing point within a protrusion from the support structure. This sensing point is located within a protrusion such that attrition of at least one cutter to a partially worn state brings the protrusion into abrasive contact with the material being cut and attrition of the protrusion then exposes the sensing point to the material which is being cut by the tool and thereby brings about a detectable change, which may include damage to the sensor at the sensing point, indicative of wear. The tool includes means to communicate data from the sensing means to the surface.

Wear sensors are provided on a drill bit or other rotary cutting tool which is for operation in a subterranean borehole and has a plurality of separate cutters protruding from a support structure towards the material to be cut by the tool. The electrically operated sensing means are located at or coupled to a sensing point within a protrusion from the support structure. This sensing point is located within a protrusion such that attrition of at least one cutter to a partially worn state brings the protrusion into abrasive contact with the material being cut and attrition of the protrusion then exposes the sensing point to the material which is being cut by the tool and thereby brings about a detectable change, which may include damage to the sensor at the sensing point, indicative of wear. The tool includes means to communicate data from the sensing means to the surface.