Abstract: Downhole tools for earth-boring applications may include a component of a steel material and including a bore. An inner surface defining the bore may be treated with a surface treatment. The surface treatment may include a nitrided region having nitrogen diffused into the steel material and a ceramic material adjacent to the nitrided region; the ceramic material defining the inner surface. Methods of making downhole tools for earth-boring applications may involve exposing a component of the downhole tool to an elevated temperature to heat the component in a nitrogen-rich environment. Nitrogen may be diffused into a steel material of the component and a nitrided region may be formed at one or more surfaces of the component. A ceramic material may be coated on the nitrided region of the component.

Abstract: Downhole tools for earth-boring applications may include a component of a steel material and including a bore. An inner surface defining the bore may be treated with a surface treatment. The surface treatment may include a nitrided region having nitrogen diffused into the steel material and a ceramic material adjacent to the nitrided region; the ceramic material defining the inner surface. Methods of making downhole tools for earth-boring applications may involve exposing a component of the downhole tool to an elevated temperature to heat the component in a nitrogen-rich environment. Nitrogen may be diffused into a steel material of the component and a nitrided region may be formed at one or more surfaces of the component. A ceramic material may be coated on the nitrided region of the component.

Abstract: Downhole motors include a stator, which may be formed from a steel material and comprise a bore. At least one surface of the stator may be treated with a surface treatment. The surface treatment includes a nitrided region comprising nitrogen diffused into the steel material and a ceramic material adjacent to the nitrided region; the ceramic material defining an interior surface of the stator defining the bore. Methods of making downhole motors may include exposing a stator to an elevated temperature to heat the stator in a nitrogen-rich environment. Nitrogen may be diffused into a steel material of the stator and a nitrided region may be formed at one or more surfaces of the stator. The stator may be cooled. The stator may be removed from the nitrogen-rich environment. A ceramic material may be coated on the nitrided region of the stator.

Abstract: Downhole motors include a stator, which may be formed from a steel material and comprise a bore. At least one surface of the stator may be treated with a surface treatment. The surface treatment includes a nitrided region comprising nitrogen diffused into the steel material and a ceramic material adjacent to the nitrided region; the ceramic material defining an interior surface of the stator defining the bore. Methods of making downhole motors may include exposing a stator to an elevated temperature to heat the stator in a nitrogen-rich environment. Nitrogen may be diffused into a steel material of the stator and a nitrided region may be formed at one or more surfaces of the stator. The stator may be cooled. The stator may be removed from the nitrogen-rich environment. A ceramic material may be coated on the nitrided region of the stator.

Abstract: A drill collar structure to facilitate measurement-while-drilling (MWD) techniques while at the same time having sufficient rigidity to facilitate the drilling operation is disclosed. In some embodiments, a metal structure involving openings such as slots, preferably oriented longitudinally along its axis, but also in other configurations, are disclosed to allow sufficient strength while at the same time allowing exit and entrance of electromagnetic energy. A composite structure is also disclosed which, for given layers, has adjacent fibers such as glass and carbon, so that when the layers are overlapped, glass areas overlap glass areas throughout the radial thickness of the composite tube to create “windows” for the entrance and exit of electromagnetic energy. In yet other embodiments, the drill collar can be made of a metallic frame structure with a multiplicity of openings which are filled with a composite material.

Abstract: Improved drill collars and their manufacture include the assembly of a body member formed of an appropriate high strength material, and a liner within the body. The body member will provide the majority of the strength and weight required of the drill collar, while the liner will be constructed of a material offering improved resistance to corrosion and stress corrosion cracking. The liner may be formed of a metal alloy, and may be retained within the body member by deforming the liner radially outwardly to establish an interference fit with the interior bore of the body member. A sealant may also be placed with the collar between the liner and the body member to seal any space between the two members.