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Abstract

A piston ring 1 for internal combustion engines comprises a hard film 2 formed on at least an outer circumferential sliding surface of the piston ring 1. The hard film 2 includes chromium, nitrogen and silicon as structural elements and the same crystal structure as CrN, and is composed of a crystal phase where silicon is contained in a solid solution state in a crystal lattice at an atomic ratio between 1 and 9.5 percent. The hard film may be the following film. Namely, a hard film is composed of a mixed phase of a crystal phase and an amorphous phase; the crystal phase includes chromium, nitrogen and silicon as structural elements and the same crystal structure as CrN and moreover includes silicon contained in a solid solution state in a crystal lattice; the amorphous phase includes silicon, nitrogen and chromium as structural elements; the ratio of the amorphous phase in the hard film is 4.5 percent or less; and the silicon content in the hard film is between 1 and 9.5 percent at an atomic ratio. The hard film may include aluminum, vanadium, titanium, zirconium, boron, carbon, oxygen or fluorine.

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First Claim