Abstract: A piston ring having a stainless steel base material, the base material having an upper surface, a lower surface, an inner circumferential surface and an outer circumferential surface, the surfaces each having a nitride layer formed thereon, the nitride layer each first being formed to have a compound layer and a diffusion layer, the diffusion layer of the outer circumferential surface then being exposed by removing the compound layer of the outer circumferential surface, the exposed diffusion layer thereafter having an ion-plating deposition layer of hard ceramic formed thereon, the piston ring wherein the exposed diffusion layer is entirely removed on the upper and lower corners of the upper and lower surface and the outer circumferential surface by chamfering corner regions of the nitride layer located around the upper and lower corners before the ion-plating deposition layer is formed.

Abstract: The present invention provides a piston ring and a combined structure of a piston ring and a ring groove of piston having a hard carbon film which is excellent in wear resistance, scuffing resistance, cohesion resistance relative to the piston material and in peeling resistance. The above-mentioned object of the invention is achieved by continuously forming a hard carbon film 2 containing one or more elements selected from Si, W and Ni, or all of the outer peripheral surface 4, the inner peripheral surface 5, the top surface 6 and the bottom surface 7 of the piston ring 1. The hard carbon film contains Si and has an Si-containing film serving as a primer film for the hard carbon film. A Cr film should preferably be formed as primer film for the hard carbon film. It is desirable to have an ion-plating film as a primer film formed on the outer peripheral surface of the piston ring.

Abstract: According to a first embodiment of the present invention, a piston ring 1 is provided that has a stainless steel base material 2 having an upper surface, a lower surface, an inner circumferential surface and an outer circumferential surface, the surfaces each having a nitride layer 3 formed thereon, where the nitride layer 3 each is first formed to have a compound layer 4 and a diffusion layer 5, where the diffusion layer 5 of the outer circumferential surface is then exposed by removing the compound layer 4 of the outer circumferential surface, where the exposed diffusion layer 5 has thereafter an ion-plating deposition layer 8 of hard ceramic formed thereon. The piston ring 1 is characterized in that the exposed diffusion layer 5 is removed on the upper and lower corners 7 of the upper and lower surfaces and the outer circumferential surface by chamfering corner regions 6 located around the upper and lower corners 7 before the ion-plating deposition layer 8 is formed.