Piston ring

Abstract

A piston ring is formed over the entire surface with a gas nitrided layer and a hard film with a thickness of 0.5 to 30 micrometers on the gas nitrided layer at the upper and lower surfaces. The hard film comprises diamond-like carbon in which are dispersed one or more elements selected from the group consisting of silicon, titanium, tungsten, chromium, molybdenum, niobium, and vanadium. The diamond-like carbon is configured with any one of an amorphous carbon structure, an amorphous carbon structure having partly a diamond structure, or an amorphous carbon structure having partly a graphite structure. The content of the above elements is 5 to 40 atomic percent, and the hard film has a Vicker's hardness in a range from 700 to 2,000. The hard film may be formed directly on the upper and lower surfaces of the piston ring in a thickness from 0.5 to 30 micrometers

Dependencies are inferred from the claim text.