Abstract: 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.

Abstract: A piston ring 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. Si.sub.3 N.sub.4 particles are fixed in these cracks. The average size of the Si.sub.3 N.sub.4 particles is 0.8 to 3 .mu.m and the dispersion ratio of the Si.sub.3 N.sub.4 particles is 3 to 15 percent by volume.

Abstract: A chromium alloy plating film is covered on the surface of sliding members and corrosion resistant members. The chromium alloy plating film is a Cr--Mo--I type alloy plating film containing iodine in 0.1 to 1.4 percent by weight and molybdenum in 0.4 to 3.8 percent by weight.

Abstract: Each side rail of a combined oil ring, which includes a spacer-expander and two side rails, has an ion nitriding treatment layer on an outer peripheral surface of the rail. The inner peripheral surface of each rail may either be a bare surface or have either a soft surface treatment or a hard chrome plating. The upper and lower surfaces of the rail may either be a bare surface or have a soft surface treatment. The method comprises coiling a strip to form a coil, placing the coil on a jig so that only the outer peripheral surface is exposed to the ion nitriding and then cutting the coil to form the individual rails with a gap.

Abstract: A combined oil ring is comprised of a steel oil ring having a generally I-shaped section consisting of upper and lower rails and a web connecting the both rails and a coil expander for forcing the oil ring outwardly. Each of the outer circumferential sliding surfaces of the circumferential outer projecting portions in the upper and lower rails forms a nitrided surface with a hardness of Hv 900 or more, at least one of the upper and lower surfaces in the circumferential outer projecting portion forms a surface with a hardness of lower than Hv 700, and a width of the outer circumferential sliding surface is smaller than 0.25 mm. The other surface of the upper and lower surfaces forms a nitrided surface with a hardness of Hv 900 or more or a surface with a hardness of lower than Hv 700.

Abstract: In a bearing member of an internal combustion engine, having a flame sprayed surface, molybdenum or tungsten carbide is known as the material of the flame spray. The present invention aims to provide, for example a flame-sprayed piston ring with good heat-and-wear-resistance as well as a property of not seriously wearing the engine cylinder or cylinder liner. The flame sprayed layer of the present invention is composed of mainly ferrochrome powder and plus a powder of a self fluxing alloy, and additionally molybdenum. The piston ring of the present invention is suitable for heavy duty internal combustion engines, in which wear of the piston ring and cylinder are severe.

Abstract: When plating an outer surface of a cylindrical article or an inner surface of a tubular article, in order to automatically achieve centering between the article to be plated and the opposed tubular or cylindrical electrode, there is provided a novel jig for supporting the cylindrical body, either the article to be plated or the opposed electrode, at the center of the tubular body, either the opposed electrode or the article to be plated, and a method for automatically centering the cylindrical body and the tubular body by means of said jig. The jig consists of a jig receiving member having a jig supporting surface in the form of an inclined surface or a spherical surface having a center axis, and a jig member having a surface by which the jig member is to be supported which is mated with the jig supporting surface and which is coaxial with the center axis of the jig supporting member, and the pair of mating surfaces serve as electric conduction means between the cylindrical body and an external circuit.

Abstract: An electrode and an article plated, or to be plated, immersed in an electrolytic chromium-plating bath can be maintained in a normal condition even while electricity for plating is not supplied, by applying a low DC voltage of 1.27 to 2.2 volts between the electrode and the article while keeping them in the plating bath.