A drill bit button insert of the present invention that is attached to a button inserts mounted in a drill bit and performs a drilling, includes a tip body and an abrasive layer formed of a diamond sintered body harder than the tip body coated at least at the button insert working/cutting surface of the tip body, in which the abrasive layer has at least two high hardness layers and a low hardness layer having a hardness lower than that of the high hardness layer disposed between these high hardness layers from the surface side of the abrasive layer toward the tip body side.

Rotary drill bits may include on or more cutting element assemblies which include a cutter and a mounting system. In one embodiment, the mounting system includes a housing, a first bearing component disposed within the housing, and a second bearing component associated with the cutting element. In certain embodiments, the bearing components may comprise a table of superhard material bonded with a substrate. In one or more embodiments, the bearing components may include bearing surfaces that are arcuate. For example, the bearing surfaces may be substantially spherical (a portion of a sphere). The bearing components may be arranged to act as a radial bearing as well as a thrust bearing for the cutting element, enabling the cutting element to rotate about a longitudinal axis of the cutter, relative to the housing, while also enabling the longitudinal axis of the cutter to be displaced (change angles) relative to the housing.

Rotary drill bits may include on or more cutting element assemblies which include a cutter and a mounting system. In one embodiment, the mounting system includes a housing, a first bearing component disposed within the housing, and a second bearing component associated with the cutting element. In certain embodiments, the bearing components may comprise a table of superhard material bonded with a substrate. In one or more embodiments, the bearing components may include bearing surfaces that are arcuate. For example, the bearing surfaces may be substantially spherical (a portion of a sphere). The bearing components may be arranged to act as a radial bearing as well as a thrust bearing for the cutting element, enabling the cutting element to rotate about a longitudinal axis of the cutter, relative to the housing, while also enabling the longitudinal axis of the cutter to be displaced (change angles) relative to the housing.

Articles comprising at least a portion of an earth-boring tool include at least one insert and a solidified eutectic or near-eutectic composition including a metal phase and a hard material phase. Other articles include a solidified eutectic or near-eutectic composition including a metal phase, a hard material phase and a coating material in contact with the solidified eutectic or near-eutectic composition.

Articles comprising at least a portion of an earth-boring tool include at least one insert and a solidified eutectic or near-eutectic composition including a metal phase and a hard material phase. Other articles include a solidified eutectic or near-eutectic composition including a metal phase, a hard material phase and a coating material in contact with the solidified eutectic or near-eutectic composition.

Embodiments of the invention relate to polycrystalline diamond (“PCD”) fabricated by sintering a mixture including diamond particles and a selected amount of graphite particles, polycrystalline diamond compacts (“PDCs”) having a PCD table comprising such PCD, and methods of fabricating such PCD and PDCs. In an embodiment, a method includes providing a mixture including graphite particles present in an amount of about 0.1 weight percent (“wt %”) to about 20 wt % and diamond particles. The method further includes subjecting the mixture to a high-pressure/high-temperature process sufficient to form PCD.

Embodiments of the invention relate to polycrystalline diamond (“PCD”) fabricated by sintering a mixture including diamond particles and a selected amount of graphite particles, polycrystalline diamond compacts (“PDCs”) having a PCD table comprising such PCD, and methods of fabricating such PCD and PDCs. In an embodiment, a method includes providing a mixture including graphite particles present in an amount of about 0.1 weight percent (“wt %”) to about 20 wt % and diamond particles. The method further includes subjecting the mixture to a high-pressure/high-temperature process sufficient to form PCD.

The method for determining fracture toughness includes clamping a cutting element in a first orientation, exerting a confining pressure on the cutting element, applying a first load at a first distance from a perimeter of the diamond table of the cutting element, increasing the first load to a first level sufficient to fracture, and recording the first level sufficient to fracture. Then, another load is applied at another distance from a perimeter of the diamond table with another cutting element or the same cutting element in another orientation. The load is increased until fracture again. The steps are repeated at different distances and different orientations to create a profile of the fracture toughness of the cutting element. The method also includes wearing the cutting element and measuring fracture toughness at a worn distance. The profile is a more complete rating of the cutting element under drilling conditions.

The method for determining fracture toughness includes clamping a cutting element in a first orientation, exerting a confining pressure on the cutting element, applying a first load at a first distance from a perimeter of the diamond table of the cutting element, increasing the first load to a first level sufficient to fracture, and recording the first level sufficient to fracture. Then, another load is applied at another distance from a perimeter of the diamond table with another cutting element or the same cutting element in another orientation. The load is increased until fracture again. The steps are repeated at different distances and different orientations to create a profile of the fracture toughness of the cutting element. The method also includes wearing the cutting element and measuring fracture toughness at a worn distance. The profile is a more complete rating of the cutting element under drilling conditions.

A drill bit for percussive rock drilling tools includes a drill bit head having a front surface including a face surface defining a forward-most end of the drill bit head and at least one hole in the drill bit head for receiving a button. The drill bit includes at least one recess located in the face surface. The recess is larger than the hole. The hole is disposed in the recess so that an open end of the hole is disposed below the face surface. The drill bit head further includes a gauge surrounding the face surface, the recess being partially disposed in the gauge.