A fracture-separated engine component and a method for manufacturing same is described. The engine component includes first and second parts each having a fracture surface extending along a fracture plane. Prior to fracture separation, the engine component is case-hardened by nitriding and has a nitriding hardness depth of 0.4 to 0.7 mm. After the nitriding, the engine component is cooled such that each one of the subsequent fracture surfaces reaches a temperature below 100 C. The fracture separation is then performed. After, the engine component has two fracture surfaces along a fracture plane, the fracture surfaces having hardened peripheral areas and unhardened core sections. No point of the unhardened core sections located in the fracture plane is located at a distance greater than 1.1 mm from a nearest hardened peripheral area. Each one of the fracture surfaces includes elongated partial fracture surfaces with a width of less than 3.2 mm.

A cooling system includes a refrigerant compressor and a first operating medium, which includes a mixture of refrigerant and lubrication oil. An oil separator reduces the percentage of the refrigerant in the operating medium so that a second lubrication oil enriched operating medium is provided by the oil separator, the provided second operating medium having at least in a second operating state a viscosity ratio of K>1.

A cooling system includes a refrigerant compressor and a first operating medium, which provides a mixture of refrigerant and lubrication oil. An oil separator reduces the percentage of the refrigerant in the operating medium to a value between 25% by weight and 80% by weight.

A member for guiding an element mobile in oscillation or rotation is presented. The member has a body made of a hardened metallic material, provided with a bore for assembling the mobile element, having cavities that are distributed discontinuously in the bore and capable of acting as grease reserves, and having optional grease supply. In the bore are defined a bearing surface outside of the cavities and the grease supply, and a non-bearing surface in the cavities and the grease supply. The bore includes at least one zone with: cavities having a depth of between 2 and 5 mm, and a quantity of grease in the cavities per bearing surface of between 0.05 and 0.3 g/cm.sup.2. A mechanical system having such a member and a method for manufacturing such a member is also contemplated.

A fracture-separated engine component and a method for manufacturing same is described. The engine component includes first and second parts each having a fracture surface extending along a fracture plane. Prior to fracture separation, the engine component is case-hardened by nitriding and has a nitriding hardness depth of 0.4 to 0.7 mm. After the nitriding, the engine component is cooled such that each one of the subsequent fracture surfaces reaches a temperature below 100 C. The fracture separation is then performed. After, the engine component has two fracture surfaces along a fracture plane, the fracture surfaces having hardened peripheral areas and unhardened core sections. No point of the unhardened core sections located in the fracture plane is located at a distance greater than 1.1 mm from a nearest hardened peripheral area. Each one of the fracture surfaces includes elongated partial fracture surfaces with a width of less than 3.2 mm.

In a manufacturing process of a corrugated cage, an intermediate assembly 17a is configured by press-fitting each of press-fitting portions 24 and 24 respectively provided in base end portions of rod portions 13b and 13b of rivets 9b and 9b into each of through-holes 12a and 12a of a cage element 8a on one side, and nitriding treatment is performed on the intermediate assembly 17a. An axial dimension X of each of the press-fitting portions 24 and 24 is made smaller than an axial dimension Y of each of the through-holes 12a and 12a (X<Y). In this way, portions which do not come into close contact with each other are provided in axial portions of the inner peripheral surface of each of the through-holes 12a and 12a and the outer peripheral surface of each of the rod portions 13b and 13b, and thus a nitrided layer is formed on each of these portions which do not come into close contact with each other.

A sliding member is capable of moving relative to a counterpart and includes a substrate and an amorphous carbon film which is provided on the substrate. The amorphous carbon film has a nitrogen content of 2 at % to 11 at % and a surface hardness in a range of 25 GPa to 80 GPa.

A mechanical component has a surface and is made of steel subjected to quenching and tempering. The mechanical component includes a nitrided layer formed at the surface. Steel contains at least 0.95 mass % and at most 1.10 mass % of carbon, less than 0.30 mass % of silicon, less than 0.50 mass % of manganese, less than 0.0080 mass % of sulfur, at least 1.3 mass % and at most 1.6 mass % of chromium, and a remainder composed of iron and an inevitable impurity. An average nitrogen concentration at the surface is equal to or more than 0.10 mass %. A hardness at the surface is equal to or more than 850 Hv. An amount of retained austenite at the surface is equal to or less than 20 volume %.