PURPOSE: To improve abrasion resistance and achieve a low friction coefficient for an inner surface of a cylinder and a sliding surface of a piston by composing either of them of a layer of fine composite ceramic including chrome oxide for matrix, and the other of SiAlON or Si3N4.

CONSTITUTION: For execution in a four-cycle reciprocatory engine, inside a cylinder block 1 is inserted a cylinder liner 3 of cast iron having a fine layer of composite ceramic(CDC) including chrome oxide for matrix formed on an inner surface 2. A piston ring 6 of Si3N4 or sintered matter of SiAl is engaged in a groove 5 provided in an outer surface of a piston 4 engaged freely reciprocatorily in this cylinder. A friction coefficient becomes low between the inner surface 3 of the cylinder liner and the sliding surface of the piston ring 6 to prevent production of friction, while sufficient sliding performance is secured even in case of lack of lubricating oil.