The present invention relates to a diamond-like coating for piston ring surfaces, comprising, an underlayer, a gradient layer and an AM layer, wherein the AM layer is a diamond-like coating doped with doping elements. The doping elements are one or a combination of at least two selected from the group consisting of Cr, Si and Ti, and the content thereof shows a cyclical change in a form of a sine wave fluctuation along with the thickness change of the AM layer. As compared with the conventional single-layer structure or gradient layer structure, the AM layer of such diamond-like coating has a multi-cycle transition structure since the content of the doping elements in the AM layer of such diamond-like coating shows a cyclical change in a sine wave fluctuation form. On the basis of having high wear-resistant and low friction coefficient, it is beneficial to decrease the internal stress of the coating, increase the tenacity of the coating, ensure the increase of the thickness of diamond-like coating, and improve the durability of piston ring of diamond-like coating at the same time.

The present invention relates to a diamond-like coating for piston ring surfaces, comprising, an underlayer, a gradient layer and an AM layer, wherein the AM layer is a diamond-like coating doped with doping elements. The doping elements are one or a combination of at least two selected from the group consisting of Cr, Si and Ti, and the content thereof shows a cyclical change in a form of a sine wave fluctuation along with the thickness change of the AM layer. As compared with the conventional single-layer structure or gradient layer structure, the AM layer of such diamond-like coating has a multi-cycle transition structure since the content of the doping elements in the AM layer of such diamond-like coating shows a cyclical change in a sine wave fluctuation form. On the basis of having high wear-resistant and low friction coefficient, it is beneficial to decrease the internal stress of the coating, increase the tenacity of the coating, ensure the increase of the thickness of diamond-like coating, and improve the durability of piston ring of diamond-like coating at the same time.

A sliding element for use in an internal combustion engine may include a ferrous base having a peripheral sliding surface covered by a protective surface layer, the protective surface layer including at least one nitride applied via at least one of physical vapour deposition and a nitrided layer. The peripheral sliding surface may have a diamond like carbon (DLC) coating disposed thereon. The coating may include at least one of (a) one or more transition layers composed of WC1-x and (b) an adhesive layer of metallic chromium with a crystal structure. The coating may include an intermediate layer of metal DLC, the metal may be tungsten in a multilayer structure of a-C:H:W and a-C:H, and an outer layer of metal-free DLC.

A sliding element for use in an internal combustion engine may include a ferrous base having a peripheral sliding surface covered by a protective surface layer, the protective surface layer including at least one nitride applied via at least one of physical vapour deposition and a nitrided layer. The peripheral sliding surface may have a diamond like carbon (DLC) coating disposed thereon. The coating may include at least one of (a) one or more transition layers composed of WC1-x and (b) an adhesive layer of metallic chromium with a crystal structure. The coating may include an intermediate layer of metal DLC, the metal may be tungsten in a multilayer structure of a-C:H:W and a-C:H, and an outer layer of metal-free DLC.

A sliding member includes: a base; a chromium-based hard chromium plated layer formed on the surface of the base; a hard carbon layer that is mainly composed of carbon element and is formed on the hard chromium plated layer. The hydrogen concentration of the hard chromium plated layer is equal to or less than 150 mass ppm. A method for producing the sliding member involves heating the surface of the base on which the chromium-based hard chromium plated layer has been formed at a temperature of 250° C. or more so that the hydrogen concentration of the hard chromium plated layer is equal to or less than 150 mass ppm, and thereafter forming the hard carbon layer mainly composed of carbon element on the hard chromium plated layer.

A sliding member includes: a base; a chromium-based hard chromium plated layer formed on the surface of the base; a hard carbon layer that is mainly composed of carbon element and is formed on the hard chromium plated layer. The hydrogen concentration of the hard chromium plated layer is equal to or less than 150 mass ppm. A method for producing the sliding member involves heating the surface of the base on which the chromium-based hard chromium plated layer has been formed at a temperature of 250° C. or more so that the hydrogen concentration of the hard chromium plated layer is equal to or less than 150 mass ppm, and thereafter forming the hard carbon layer mainly composed of carbon element on the hard chromium plated layer.

A piston ring for an internal combustion engine may include a metal base and a protective coating disposed on the base to cover at least part of a surface of the base. The coating may be composed of at least one nitride phase formed from at least one metal element and aluminum, and the coating may have an internal stress of less than 1.2 GPa.

A piston ring for an internal combustion engine may include a metal base and a protective coating disposed on the base to cover at least part of a surface of the base. The coating may be composed of at least one nitride phase formed from at least one metal element and aluminum, and the coating may have an internal stress of less than 1.2 GPa.

A coated sliding member 10 for use under an environment where it is in contact with lubricant, comprising: a base material 12; and a first hard carbon layer 14 having a thickness of 3 μm or more formed on a surface of the base material by a vacuum arc method using carbon and consisting of diamond-like carbon, containing substantially no hydrogen and being configured only of carbon, and a second hard carbon layer 15 formed on a surface of the first hard carbon layer by a vacuum arc method using carbon and consisting of diamond-like carbon, containing substantially no hydrogen and being configured only of carbon and nitrogen, the film thickness of the second hard carbon layer being 3 to 35% of the film thickness of the first hard carbon layer.

A coated sliding member 10 for use under an environment where it is in contact with lubricant, comprising: a base material 12; and a first hard carbon layer 14 having a thickness of 3 μm or more formed on a surface of the base material by a vacuum arc method using carbon and consisting of diamond-like carbon, containing substantially no hydrogen and being configured only of carbon, and a second hard carbon layer 15 formed on a surface of the first hard carbon layer by a vacuum arc method using carbon and consisting of diamond-like carbon, containing substantially no hydrogen and being configured only of carbon and nitrogen, the film thickness of the second hard carbon layer being 3 to 35% of the film thickness of the first hard carbon layer.