| abstract |
A gas nitrided layer 2 is formed over the entirensurface of a piston ring 1 and a hard film 3 with anthickness of 0.5 to 10 micrometers is formed on the gasnnitrided layer 2 at the outer circumferential surface.nThe hard film 3 comprises diamond-like carbon in whichnare dispersed carbides of one or more elements selectednfrom the group consisting of silicon, titanium,ntungsten, chromium, molybdenum, niobium, and vanadium.nThe diamond-like carbon is configured with any one of annamorphous carbon structure, an amorphous carbonnstructure having partly a diamond structure, or annamorphous carbon structure having partly a graphitenstructure. The content of the above elements is 5 to 40natomic percent, and the hard film 3 has a Vicker'snhardness in a range from 700 to 2,000. A chromiumnplating film or ion plating film may be used instead ofnthe gas nitrided layer 2. The hard film 3 may be formedndirectly on the outer circumferential surface of thenpiston ring 1 in a thickness from 10 to 30 micrometers. |