Composite chromium plating film and sliding member covered thereof

摘要

A piston ring is formed with a nitrided layer over all surfaces and formed with a composite chromium plating film over the nitrided layer in the outer circumferential surface. The composite chromium plating film has a network of cracks formed on the outer surface and interior. Spherical alumina particles are fixed in these cracks. The average size of the spherical alumina particles is 0.7 to 10 mu m and the dispersion ratio of the spherical alumina particles is 3 to 15 percent by volume.