Cylinder barrel

A system, comprising:

• a pump having a pump housing;
• a cylinder barrel configured to rotate within the pump housing, the cylinder barrel including:
• a main cylindrical body;
• a center recess defined within the main cylindrical body configured to seat a drive shaft therein;
• and
• a plurality of bores defined in the main cylindrical body, extending in an axial direction, wherein the plurality of bores are spaced apart circumferentially relative to one another about the main cylindrical body radially outward of the center recess, and wherein the plurality of bores are each configured to seat a respective piston therein and allow fluid flow therethrough,
• wherein the main cylindrical body is formed of silicon nitride, wherein each respective piston further includes a ring disposed at an end thereof configured to form a hydrodynamic seal with an inner surface of a respective bore, wherein the ring is made of tool steel.