Rigid composite structure with a superhard interior surface

A rigid composite structure, comprising:

• a bore formed in a metallic material and comprising a longitudinal axis;
• a tubular body formed by geometric segments comprising a superhard interior surface wherein the superhard interior surface comprises a material selected from the group consisting of natural diamond, synthetic diamond, polycrystalline diamond, single crystalline diamond, cubic boron nitride, and composites thereof with a binder, the segments being disposed adjacent one another substantially co-axial along the longitudinal axis within at least a portion of the bore;
• and
• the superhard interior surface is under a radial and axial compression;
• wherein the superhard interior surface comprises a geometry formed by electrical discharge machining;
• and
• the superhard interior surface comprises a region extending radially from the interior surface throughout the entire tubular body that is depleted of a binder material.