Abstract: A piston ring in cast tool steels including a ring of a tempered material having a chemical composition including a percent weight concentration of C from 0.80 to 1.40, Cr from 2.50 to 4.20, Mn from 0.10 to 1.00, Mo from 1.00 to 2.00, Nb from 2.50 to 4.50, P of no more than 0.05, S of no more than 0.05, Si from 0.10 to 1.00, Ti from 0.10 to 0.30, V from 1.00 to 3.00, W from 1.00 to 3.00, and a remaining concentration balance of Fe. The tempered material may have a microstructure including a matrix of tempered martensite with precipitation of at least one of secondary M2C carbides and MC carbides, M being at least one of V, Mo, Cr, and W. The microstructure may include NbC eutectic carbides having a cubic morphology. The tempered material may have a hardness from approximately 400 HV to 800 HV.

Abstract: A piston ring in cast tool steels including a ring of a tempered material having a chemical composition including a percent weight concentration of C from 0.80 to 1.40, Cr from 2.50 to 4.20, Mn from 0.10 to 1.00, Mo from 1.00 to 2.00, Nb from 2.50 to 4.50, P of no more than 0.05, S of no more than 0.05, Si from 0.10 to 1.00, Ti from 0.10 to 0.30, V from 1.00 to 3.00, W from 1.00 to 3.00, and a remaining concentration balance of Fe. The tempered material may have a microstructure including a matrix of tempered martensite with precipitation of at least one of secondary M2C carbides and MC carbides, M being at least one of V, Mo, Cr, and W. The microstructure may include NbC eutectic carbides having a cubic morphology. The tempered material may have a hardness from approximately 400 HV to 800 HV.

Abstract: A piston ring for at least one of a piston of an internal combustion engine and a compressor may include at least one substantially annular metallic base having a nitrided layer. The base may include at least one chamfer and at least one outer surface that maintains contact with a layer of lubricating oil. The nitrided layer may exhibit a substantially constant thickness over at least one surface of the base and the at least one chamfer. The nitrided layer may include a nitrided diffusion layer that maintains direct contact with the layer of lubricating oil and has a residual tension ranging from +100 megapascal to ?100 megapascal.

Abstract: A piston ring for at least one of a piston of an internal combustion engine and a compressor may include at least one substantially annular metallic base having a nitrided layer. The base may include at least one chamfer and at least one outer surface that maintains contact with a layer of lubricating oil. The nitrided layer may exhibit a substantially constant thickness over at least one surface of the base and the at least one chamfer. The nitrided layer may include a nitrided diffusion layer that maintains direct contact with the layer of lubricating oil and has a residual tension ranging from +100 megapascal to ?100 megapascal.

Abstract: A piston ring for internal combustion engines with a coating of Chromium nitride (CrN) deposited by a physical vapor deposition process on a sliding surface with a typical crystal structure of CrN phase, has a high wear resistance and superior resistance to the generation of micro-cracks and consequent localized loss of pieces of the coating. The coating is a columnar crystalline coating of CrN having a dispersed pore content lower than 10% in volume and ratio of intensities, measured through x-ray diffraction, between the crystal planes (111) and planes (200), parallel to the surface, in the range of 0.40 to 0.70. This crystalline distribution is obtained through an oxygen content impregnated in the CrN coating between 1.0% in weight to 7.0% in weight. The Vickers hardness of the film ranges from 1,500 to 2,200 HV.