In a surface of a wire, a first side surface forming an outer circumferential surface in a piston ring includes a tapered surface and a protruding surface, the protruding surface is divided into a first part and a second part by a first virtual surface extending from the tapered surface, and the first part includes a top and is formed in a protruding shape.

A sliding mechanism of the present invention includes a cylinder bore having a thermally sprayed iron-based coating and includes a piston with a piston ring covered with a hard coating composed mainly of carbon. The thermally sprayed coating has diamond abrasive grains. An area ratio of the diamond abrasive grains to a surface of the thermally sprayed coating is 0.3 to 1.8%, which enables suppressing wear of the piston ring having the hard coating composed mainly of carbon.

A ringset is configured to be arranged on a piston for sealing a gas in a high-pressure region of a cylinder in the absence of oil or other liquid lubricant. The ringset includes one or more rings made from a high-strength material as a sealing element. The ringset also includes a solid lubricant applicator configured to provide lubrication between the one or more rings and a bore of the cylinder. For example, the ring can support pressure loads from high-pressure gas without breaking, while the applicator need not act as a seal. As the piston reciprocates in the bore, the applicator slides against the bore and applies solid lubricant material to the bore, resulting in a solid lubricant film on the bore against which the sealing element may slide. The applicator includes a material such as a graphite, a polymer, or other suitable solid lubricant.

A ringset is configured to be arranged on a piston for sealing a gas in a high-pressure region of a cylinder in the absence of oil or other liquid lubricant. The ringset includes one or more rings made from a high-strength material as a sealing element. The ringset also includes a solid lubricant applicator configured to provide lubrication between the one or more rings and a bore of the cylinder. For example, the ring can support pressure loads from high-pressure gas without breaking, while the applicator need not act as a seal. As the piston reciprocates in the bore, the applicator slides against the bore and applies solid lubricant material to the bore, resulting in a solid lubricant film on the bore against which the sealing element may slide. The applicator includes a material such as a graphite, a polymer, or other suitable solid lubricant.

A piston ring includes a base body having an inner circumferential surface, first and second flank surfaces and an outer circumferential surface, wherein a first hard chromium layer with a crack network is applied to the outer circumferential surface and has a crack density of 10-250 cracks per mm and solid particles having an average particle size of 0.01-10 μm embedded in cracks of the first hard chromium layer, a second hard chromium layer having a crack network applied to the first hard chromium layer and having a crack density of the crack network of 10-250 cracks per mm, no solid particles being embedded in the cracks thereof, where the cracks have an average width of 1-15 μm, the cracks are electrolytically expanded and the surface proportion of the cracks are 3-25% based on a total surface of the second hard chromium layer.

A piston ring includes a base body having an inner circumferential surface, first and second flank surfaces and an outer circumferential surface, wherein a first hard chromium layer with a crack network is applied to the outer circumferential surface and has a crack density of 10-250 cracks per mm and solid particles having an average particle size of 0.01-10 μm embedded in cracks of the first hard chromium layer, a second hard chromium layer having a crack network applied to the first hard chromium layer and having a crack density of the crack network of 10-250 cracks per mm, no solid particles being embedded in the cracks thereof, where the cracks have an average width of 1-15 μm, the cracks are electrolytically expanded and the surface proportion of the cracks are 3-25% based on a total surface of the second hard chromium layer.

A sliding element, in particular a piston ring, includes a base material of martensitic or austenitic stainless steel having a chromium content of at least 6.0% by mass and a nitrided layer having a surface hardness of up to 950 HV1. A method of producing such a sliding layer is also provided.

A sliding element, in particular a piston ring, includes a base material of martensitic or austenitic stainless steel having a chromium content of at least 6.0% by mass and a nitrided layer having a surface hardness of up to 950 HV1. A method of producing such a sliding layer is also provided.

An engine component, for example a piston ring, including a wear resistant coating applied by physical vapor deposition (PVD) is provided. The coating includes tetrahedral amorphous carbon (ta-C), the carbon of the coating includes sp.sup.3 hybrid orbitals, and the coating includes boron in an amount of 0.1 wt. % to 4.0 wt. %, based on the total weight of the coating. The doped boron makes the coating less sensitive to the ion energy during the physical vapor deposition (PVD) process, improves adhesion of the coating, and expected to reduce compressive stress in the coating. Thus, the boron-doped ta-C coating can be applied to a greater thickness compared to ta-C coatings without the doped boron. In addition, there is a strong indication that the addition of boron will maintain a high level of sp.sup.3 bonded carbon and a high microhardness.

An engine component, for example a piston ring, including a wear resistant coating applied by physical vapor deposition (PVD) is provided. The coating includes tetrahedral amorphous carbon (ta-C), the carbon of the coating includes sp.sup.3 hybrid orbitals, and the coating includes boron in an amount of 0.1 wt. % to 4.0 wt. %, based on the total weight of the coating. The doped boron makes the coating less sensitive to the ion energy during the physical vapor deposition (PVD) process, improves adhesion of the coating, and expected to reduce compressive stress in the coating. Thus, the boron-doped ta-C coating can be applied to a greater thickness compared to ta-C coatings without the doped boron. In addition, there is a strong indication that the addition of boron will maintain a high level of sp.sup.3 bonded carbon and a high microhardness.