| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston ring excellent in sliding characteristics such as adhesion performance against aluminum, seizure resistance, initial conformable fittability. SOLUTION: Diamond-like carbon films 4 are formed directly on the upper and lower surfaces of a piston ring 1, or formed on a hard surface-treated layer of a gas nitriding layer 2 or Cr-plated film 5, through substrate films 3, by the thickness ranging between 0.5 and 30 micrometers. The diamond-like carbon has a state selected from the followings: (1) amolphous carbon structure, (2) amolphous carbon structure partially containing diamond structure, (3) amolphous carbon structure partially containing graphite structure. The substrate film is composed of one or two elements selected from Si, Ti, W, Cr, Mo, Nb, V by not less than 70 atom % and less than 100 atom %, and remainder carbon. Or, it is composed of the selected element (s) of 100 atom %. The same film can be formed on an outer peripheral surface of the piston ring 1.
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