Abstract: A piston ring for an engine may include a piston ring body. The piston ring body may include a working surface, a lower surface, an upper surface, and an inner surface. An area of the working surface and/or the lower surface which is close to an outer circumferential lower edge of the piston ring body is not provided with a nitride layer, the outer circumferential lower edge is formed with a chamfer, the chamfer does not have a nitride layer, and an additional area of the piston ring has a nitride layer.

Abstract: A three-part oil scraper ring includes an expander spring and two scraper rings, comprising a ring body (4) having an upper flank (6), a lower flank (8), a ring inner surface (10) and a ring outer surface (12) which has a ring outer contour (14) in cross-section in axial direction (A). The ring body (4) has a height H which corresponds to the greatest distance of the upper flank (6) to the lower flank (8). The ring outer contour (14) forms a running surface (16) which has a radius of curvature R which is smaller than the height H of the scraper ring (2) by a factor between 1.5 to 6, preferably between 3 to 5 and further preferably between 3.5 to 4.5.

Abstract: A piston ring that is pre-treated by grit blasting to a defined roughness, followed by PVD coating with a metal nitride to a thickness of at least 10 ?m, leaving peaks and valleys in the coated piston ring. The coated piston ring is then lapped to remove the peaks without penetrating the coating, so that valleys and plateaus remain in the coated surface. The resulting piston ring exhibits superior coating retention due to the increased surface area created by the grit blasting, and yet also superior performance, as the cavities remaining increase the porosity of the coating and thus enhance the lubrication of the ring.

Abstract: The invention provides a manufacturing method for thin-wall bearing and a method for machining a thin-wall inner ring/outer ring as well as a precision flexible bearing. The method for machining the thin-wall inner ring/outer ring comprises the following steps of: S0, providing a thin-wall ring with machining allowance left; S1: reinforcing along the radial direction and/or axial direction of the thin-wall ring; S2: carrying out quenching-tempering heat treatment on the reinforcing ring obtained by reinforcement in the S1; S3: carrying out corresponding grinding, hard cutting and super finishing on the reinforcing ring after receiving heat treatment, which includes removal of the machining allowance and a reinforcing part obtained by reinforcement in the S1, thereby obtaining finished thin-wall ring product. The thin-wall ring reinforced machining method substantially reduces and even avoids deformation of the thin-wall ring in all manufacturing links, thereby obtaining very high machining precision.

Abstract: A hydraulic machine is described having a first part (2) and a second part (3) moveable relative to said first part (3), one of said first part (2) and said second part (3) having a first land (9) resting against the other one of said second part (3) and said first part (2), having a predetermined first height (H1), and being arranged between a high pressure area (7) and a low pressure area (8). Such a machine should have a long working life. To this end a second land (10) having a predetermined second height (H2) smaller than said first height (H1) is located adjacent to said first land (9).

Abstract: A piston ring may have a base with a sliding external surface, an internal surface, an upper surface, and a lower surface, the external surface having chamfered edges. The external surface, the internal surface, the upper surface, the lower surface, and the chamfered edges may have a coating provided with a nitrided first layer having a thickness of up to 2% of a nominal axial thickness of the ring when applied to the upper surface and the lower surface, and a thickness of up to 10% in relation to the thickness of the first layer applied to the upper surface and the lower surfaces when applied to the external surface and to the chamfered edges. The external surface and the chamfered edges may include a sliding layer having one of a hard chromium or ceramic chromium plated coating, the sliding layer being applied on the first layer, the sliding layer having a thickness of between 80 and 175 microns.

Abstract: A sliding element, in particular a piston ring has an outer circumferential running surface of the piston ring, has no nitriding layer, preferable no surface hardening the running surface has as an outermost layer, which differs from the intermediate layer, a DLC layer or a metal-based nitride layer, preferable a metal nitride layer, preferably a CrN layer. Provided between the substrate of the sliding element and the DLC layer there is at least one metal-containing intermediate layer, preferably a metal layer, particularly preferable a chromium layer, and at least one further surface of the sliding element, preferably the piston ring flanks, is surface-hardened, preferably has a nitriding layer.

Abstract: A piston ring for a piston of an internal combustion engine may include a body composed of a ferrous material. The body may have an upper portion, a lower portion opposed to the upper portion, an internal portion configured to face towards a piston groove and an external portion opposed to the internal portion. An upper chamfer may be disposed between the upper portion and the external portion. A lower chamfer may be disposed between the lower portion and the external portion. The upper portion, the lower portion and the internal portion may each have a nitrided layer. The external portion, the upper chamfer and the lower chamfer may include at least one ion plated coating layer. The nitrided portion in at least a superficial layer may have a hardness of 700 HV or less.

Abstract: A method for producing a piston ring for a cylinder that moves in a sliding direction includes providing a piston ring base material having an upper surface, a lower surface and an outer circumferential surface having a first recess between the upper surface and the lower surface, forming a hard film in the first recess and on a cylindrical surface at a predetermined thickness, and removing, by performing a polishing process on the sliding surface, the hard film formed on the cylindrical surface and a part of the piston ring base material disposed adjacent to the removed hard film, to form a second recess. The second recess is formed by removing an area of the removed part of the piston ring base material as a result of polishing the sliding surface due to a difference in the hardness of the hard film and the piston ring base material.

Abstract: A sliding element, for example a piston ring for an internal combustion engine, may include a sliding face, an adhesive layer disposed on the sliding face, and a coating disposed over the adhesive layer. The coating may be composed of an amorphous carbon material. The coating may have a ratio between sp3 bonds and sp2 bonds that indicates a predominance of sp2 bonds. The coating may have a roughness profile including a value of Rpk of ?0.15 ?m and a value of Rz of 0.7?Rz?1.5 ?m.

Abstract: A piston ring may include a stainless steel base having between 8% and 15% by weight of chromium, together with other elements and impurities, and having a hardness between 350 HV and 420 HV. The piston ring may also include a superficial nitrided layer having a depth of no more than 60 ?m and an average hardness measured upon the surface exceeding 800 HV. The nitrided layer may include a plurality of nitride particles, which may have a maximum size of 5 ?m and may be distributed over between 4% and 8% of an area of the nitrided layer.

Abstract: A piston ring is produced in which a piston ring base body made of cast iron or cast steel is coated with at least one PVD layer having a variable layer thickness, such that an increased layer thickness is present in the region of the ring ends compared to the remaining circumferential region of the piston ring base body, wherein the piston ring base body is configured so that, in the cold operating state with the engine not running, the radial pressure distribution of the piston ring base body is such that the ring ends exhibit substantially no radial pressure across a defined circumferential angle, and the variable layer thickness of the PVD layer is set so that a substantially uniform radial pressure distribution is present along the entire ring circumference of the piston ring at a piston ring temperature above 150° C.

Abstract: A graphite cast iron nitrided piston ring has a main body including matrix and a nitrided layer. The matrix is made of graphite cast iron, and the nitrided layer is formed by subjecting a surface of the matrix to contact a cylinder to a gas nitriding process. With the nitrided layer formed at the surface of the matrix made of graphite cast iron, the piston ring has sufficient hardness and good abrasion resistance.

Abstract: Disclosed is a method and apparatus for forming a coating layer using a physical vapor deposition apparatus equipped with a sputtering apparatus and an arc ion plating apparatus, comprising: a first coating step of forming a Mo coating layer on a base material using a the sputtering apparatus and a Mo target and Ar gas; a nitrating step of forming a nitride film forming condition using an arc ion plating apparatus and Ar gas and N2 gas; a second coating step of forming a nano composite coating layer of Cr—Mo—N using the Mo target and Ar gas of the sputtering apparatus and the Ar gas, N2 gas and a Cr source of the arc ion plating apparatus at the same time; and a multi-coating step of forming a multi-layer having alternating Cr—Mo—N nano composite coating layers and Mo coating layers by revolving the base material around a central pivot.

Abstract: Provided is a sliding member capable of achieving excellent wear resistance and high coating adhesion under harsh sliding conditions without subjecting a base member to nitriding treatment. The sliding member includes a base member made of a steel material and a hard coating that is formed on the base member and having a surface serving at least as a sliding surface. The hard coating has a Young's modulus having a distribution to increase first in a depth direction directed from an interface between the hard coating and the base member to the surface, to become maximum at a predetermined depth, and then to decrease in the depth direction directed from the interface to the surface.

Abstract: A piston ring may include a metallic base, an outer slide layer and an intermediate layer disposed between the base and the outer slide layer. The base may extend between at least two end regions. The outer slide layer and the intermediate layer may be disposed on an outer radial face of each end region of the base.

Abstract: 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.

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 exhibiting particles capable of wear resistance on its shoulder is produced by producing a melt of the base materials of a metal material, adding ceramic particles to the melt, pouring the melt into a prefabricated mold and cooling the melt. During cooling, the mold is aligned such that the ceramic particles gather on at least one of the piston ring shoulders.

Abstract: The present invention refers to a piston ring, particularly for use in the piston channel of an internal combustion engine or a compressor, comprising at least a substantially ring-shaped metallic base (2) having at least a first region (20), at least a second region (21) and at least a gap (22), the first region (20) being positioned in a way substantially opposite to the gap (22), the ring comprising at least a nitrided layer (3) in the second region (21) and comprising at least reduction of the nitrided layer (3) in the first region (20), whereas the reduced nitrided layer (3) is at least partially blocked in the first region (20) due to the previous application of an intermediate layer (4).

Abstract: A piston ring, is produced by providing, on the radially outer circumferential surface of a ring-shaped metallic main body, a recess, the metallic main body having a radially outer circumferential surface, a radially inner circumferential surface, and flank surfaces interposed therebetween providing the recess with a contour that deviates from a cylindrical shape at least on the bottom of the recess, providing at least one wear-resistant layer on the outer circumferential surface, including the recess, and at least partially removing an area of the at least one wear-resistant layer on the outer circumferential surface and including an area corresponding to a scraping edge, thereby forming a land having a predefinable width.

Abstract: A piston ring is produced by providing a metallic main body, at least including a radially outer running surface, a radially inner circumferential surface and upper and lower flank surfaces interposed therebetween, with a defined taper in the region of an approximately cylindrical running surface, providing at least the running surface with at least one wear-resistant layer, and removing the at least one wear layer in the region of the entire circumference of the ring that forms a scraping edge forming a land having a predefinable width.

Abstract: A piston ring comprising upper face, a lower face, an inner perimeter wall, and an outer perimeter wall that extends around the piston ring from the upper face to the lower face, where the outer perimeter wall has upper corner region disposed adjacent the upper face, a lower corner region disposed adjacent the lower face, and a band of a nitrided conversion layer extending between the upper corner region and the lower corner region, and where a PVD nitride layer is disposed on the upper corner region and on the lower corner region.

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 coated piston ring having a base body of chromium steel with more than 10 wt.-% chromium and having an inner circumferential surface, a first flank surface, a second flank surface and an outer circumferential surface. The first flank surface comprises a nitride diffusion layer with a layer thickness of from 5-300 ?m, a nitride connecting layer with a layer thickness of from 0.5-15 ?m on the nitride diffusion layer, and an oxide layer with a layer thickness of from 0.05-3 ?m on the nitride connecting layer. The second flank surface comprises the nitride diffusion layer, and the outer circumferential surface comprises the nitride diffusion layer and a chromium solid particle layer with 0.1-30 vol.-% solid particles, relative to the total volume of the chromium solid particle layer on the nitride diffusion layer.

Abstract: Disclosed is a piston ring (1) having a substrate (10) to which a wear resistant coating (20) is applied that includes at least one first element with a melting point Tm?700° C. The wear resistant coating (20) contains at least one second element with a melting point Tm>760° C. The wear resistant coating also includes droplets (30) which have a diameter (D) and which contain at least the first element, wherein at least 90% of the droplets (30) have a value 1 ?m?D?10 ?m. In the method for producing a wear resistant coating (20) using an arc evaporation technique, the target material includes at least one first element with a melting point Tm?700° C. and at least one second element with a melting point Tm>760° C., wherein the quantity of the second material contained in the target material is such that the melting point (Tm) of the target material ?1000° C.

Abstract: A structure of a piston ring to be installed in an engine includes a matrix. A laminated intermediate layer is formed on a surface of the matrix from hard chromium (Cr), chromium nitride (CrN) and titanium carbide (TiC) in order, and a diamond-like carbon film (DLC) is coated on an outer periphery of the intermediate layer. Thus, the piston ring is wrapped by a skin with a progressive structure having a gradient distribution of hardness. The structure formed from the diamond-like carbon film provides a low wear rate and a low friction coefficient, while applying a high bonding force to the matrix and making the piston ring have an improved normal service life that meets the related environmental regulations.

Abstract: A high-quality internal combustion engine oil ring which stably keeps oil consumption low for a long period and in which the shapes of an upper rail and a lower rail can be formed at low cost with high accuracy. The internal combustion engine oil ring has a recessed stepped portion formed at a corner of a sliding surface of an outer peripheral sliding projection in sliding contact with a cylinder inner wall surface of at least one of a first rail and a second rail constituting an oil ring main body, in a shape in vertical cross-section along a sliding direction of the first rail and second rail, and a wall surface of the recessed stepped portion has an arcuate surface having a radius of curvature of 0.02 mm to 0.08 mm.

Abstract: A piston ring comprising upper face, a lower face, an inner perimeter wall, and an outer perimeter wall that extends around the piston ring from the upper face to the lower face, where the outer perimeter wall has upper corner region disposed adjacent the upper face, a lower corner region disposed adjacent the lower face, and a band of a nitrided conversion layer extending between the upper corner region and the lower corner region, and where a PVD nitride layer is disposed on the upper corner region and on the lower corner region.

Abstract: A method for producing a recessed steel piston ring provided with a wear-resistant layer includes generating a main body that has a recess on the running surface side and that, in the region where a lower flank of the main body transitions into the running surface is worked so that a chamfer is created, providing the running surface and at least portions of the chamfer with at least one wear-resistant layer, nitriding the circumferential surface and the lower and upper flanks of the main body that are not provided with the wear-resistant layer so that a section having a defined width and having no nitride layer remains on the flank adjacent the chamfer, and removing the at least one wear-resistant layer to such an extent that a substantially sharp, but unnitrided functional edge is created in the region where the lower flank transitions into the running surface.

Abstract: A structure of a titanium-alloy piston ring is configured to be installed in an engine and includes a titanium-alloy matrix. The titanium-alloy matrix has an outer periphery receiving a hardening treatment (such as receiving a nitrogen treatment, or being coated with a diamond-like carbon film, or receiving a nitrogen treatment and then being coated with a diamond-like carbon film), so as to make the piston ring have improved abrasion-resistant strength, hardness, and wear resistance, thereby extending the normal service life of the piston ring.

Abstract: This invention refers to the solution of problem of spalling of the nitrided layer in piston rings for Flex-fuel engines, without jeopardizing the wear resistance, suggesting for such purpose a nitrided piston ring (100,100?) equipped with two nitrided layers (1,2), with metallic base (3) composed mainly of iron and whose superficial hardness presented is of about 800 Vickers, decreasing in a substantially linear manner up to about 400 Vickers for a distance to the surface of up to 90 microns (?m).

Abstract: A piston ring, is produced by providing, on the radially outer circumferential surface of a ring-shaped metallic main body, a recess, the metallic main body having a radially outer circumferential surface, a radially inner circumferential surface, and flank surfaces interposed therebetween providing the recess with a contour that deviates from a cylindrical shape at least on the bottom of the recess, providing at least one wear-resistant layer on the outer circumferential surface, including the recess, and at least partially removing an area of the at least one wear-resistant layer on the outer circumferential surface and including an area corresponding to a scraping edge, thereby forming a land having a predefinable width.

Abstract: A high-quality internal combustion engine oil ring which stably keeps oil consumption low for a long period and in which the shapes of an upper rail and a lower rail can be formed at low cost with high accuracy. The internal combustion engine oil ring has a recessed stepped portion formed at a corner of a sliding surface of an outer peripheral sliding projection in sliding contact with a cylinder inner wall surface of at least one of a first rail and a second rail constituting an oil ring main body, in a shape in vertical cross-section along a sliding direction of the first rail and second rail, and a wall surface of the recessed stepped portion has an arcuate surface having a radius of curvature of 0.02 mm to 0.08 mm.

Abstract: This invention refers to the solution of problem of spalling of the nitrided layer in piston rings for Flex-fuel engines, without jeopardizing the wear resistance, suggesting for such purpose a nitrided piston ring (100,100?) equipped with two nitrided layers (1,2), with metallic base (3) composed mainly of iron and whose superficial hardness presented is of about 800 Vickers, decreasing in a substantially linear manner up to about 400 Vickers for a distance to the surface of up to 90 microns (?m).

Abstract: The invention relates to a sliding element, in particular a piston ring, preferably made of cast iron or steel, comprising a coating having a CrN, an Me(CxNy), and a DLC layer extending from the inside to the outside, wherein the DLC layer is either metal-free or consists of a metal-containing substructure and a metal-free DLC top layer. The invention further relates to a combination of such a sliding element with an iron-based mating miming element.

Abstract: Provided is a piston ring such that it is possible to sufficiently inhibit adhesive wear when the piston ring is mounted to a piston for a diesel engine in which at least the piston ring groove in the piston is formed from steel or cast iron. Disclosed is a piston ring mounted to a piston for a diesel engine, wherein the load length ratio (Rmr2) (in accordance with JIS B0601:2001) of the top surface and bottom surface of the piston ring satisfies each of the following conditions: Rmr2 (0.5%, 0.3[mu]m)=20% and Rmr2 (0.5%, 0.4[mu]m)=40%.

Abstract: A multi-piece oil ring includes an oil ring main member in which two rails are connected together by a columnar part and which has a roughly I-shaped cross section; and a coil expander disposed in an inner circumferential groove formed on the inner circumferential surface of the columnar. Each rail in the oil ring main member possesses a sliding section protuberance whose tip possesses a jutting portion. The axial length of the jutting portion is 0.02-0.18 mm. The change rate of the axial length of the individual jutting portion is in the range of 0 to 80% at least in a region of from its sliding surface to be faced to a cylinder, which is positioned at the tip of the jutting portion, to a position of 0.03 mm away from the aforementioned sliding surface in the radial direction of the oil ring main member.

Abstract: The present invention refers to a piston ring, particularly for use in the piston channel of an internal combustion engine or a compressor, comprising at least a substantially ring-shaped metallic base (2) having at least a first region (20), at least a second region (21) and at least a gap (22), the first region (20) being positioned in a way substantially opposite to the gap (22), the ring comprising at least a nitrided layer (3) in the second region (21) and comprising at least reduction of the nitrided layer (3) in the first region (20), whereas the reduced nitrided layer (3) is at least partially blocked in the first region (20) due to the previous application of an intermediate layer (4).

Abstract: A piston ring which can sustain a superior effect of preventing aluminum cohesion for a long time in a high output engine is provided. At least one of the upper and lower side faces of a piston ring is coated with a polyimide film having hard particles dispersed therein. Employed as the hard particles may be alumina, zirconia, silicon carbide, silicon nitride, cubic boron nitride, or diamond. The hard particles are to be 0.01 to 5 ?m in average particle diameter, and the film is 2 to 30 ?m in thickness.

Abstract: A piston ring having a base body, which comprises a running surface provided with at least one chamber, an upper and a lower flank surface, and an inner circumferential surface, wherein the running surface is provided with at least one PVD layer such that the same is adjusted to the contour of the running surface without completely filling the chamber, wherein the respective edge region is provided with a layer thickness, b that is reduced compared to the layer thickness, a of the chamber as a function of the configuration of the chamber.

Abstract: A sliding element comprises at least one surface for sliding contact with a running face, wherein a wear layer and a run-in layer made from carbon are applied to the surface, and is characterized in that the run-in layer comprises hydrogen and nanocrystalline carbide phases. In a method for manufacturing a sliding element, the run-in layer is applied by means of a PVD process. A sliding system has an above-described sliding element and a body having a running face. A coating for a sliding element comprises a wear layer which can be applied to the upper side of the sliding element, and a run-in layer which is configured as a carbon layer, and is characterized in that the run-in layer comprises hydrogen and nanocrystalline carbide phases.

Abstract: There is described a piston ring, particularly devised for use in internal combustion engines or compressors, comprising at least a metallic base (2) to which there is applied, by the process of physical vapor deposition (PVD), a coating (3) of chromium nitride that comprises a periodicity (P), formed by at least two adjacent layers (5,5?), each layer (5,5?) having a predominantly chromium nitride phase different from the adjacent layer.

Abstract: A steel material composition in particular for manufacturing piston rings and cylinder liners, which has a good nitriding capability, contains the following elements in the given proportion related to 100% by weight of the steel material composition: 0.5-1.2% by weight C, 4.0-20.0% by weight Cr, 45.30-91.25% by weight Fe, 0.1-3.0% by weight Mn, 0.1-3.0% by weight Mo, 2.0-12.0% by weight Ni, 2.0-10.0% by weight Si and 0.05-2.0% by weight V. It can be manufactured by manufacturing a melt of the starting materials and casting the melt into a prefabricated mould. Nitridation of the steel material composition which is obtained leads to a nitridized steel material composition which, by virtue of the manufacture with gravity casting, exceeds the properties of tempered cast iron with nodular graphite.

Abstract: The present invention refers to a piston ring for internal combustion engine, having an outer surface of a coating of Chromium Nitride (CrN and Cr2N) and Niobium Nitride (NbN and Nb4N3), capable of offering greater resistance to peeling of the coating, also maintaining an excellent level of resistance to wear and tear and scratches to the layer of Chromium Nitride deposited.

Abstract: An oil ring Ro for an internal combustion engine according to the present invention includes at least one selected from the group consisting of hard carbon, CrN and TiN that covers an outer periphery 1 of the oil ring. A radius of curvature R at an outermost portion T of the oil ring in a sliding direction is 0.3 mm or more.

Abstract: A piston ring includes a running surface having a running surface profile, and an upper flank surface and a lower flank surface. At least the running surface is provided with a vapor-deposited layer such that part of the running surface is provided with a removable cover enabling an essentially sharp-edged running edge to be formed between the running surface and at least one of the flank surfaces, once the vapor-deposited layer has been produced and the cover has been removed.

Abstract: [Task] The chromium nitride ion-plating coating has a property that it is hard but is liable to peel off. Year by year, the required level of wear resistance and scuffing resistance becomes higher in a diesel engine. The property of a coating is improved to enhance the wear resistance and scuffing resistance and also to improve resistance against peeling off. [Means for Solution] (1) Composition is mainly composed of chromium, nitrogen, and carbon, and the concentration of carbon relative to the total concentration of the main components is from 4 to 8% by weight. (2) The crystal structure is that texture of the CrN (111) plane orientation is from 0.4 to 2.0 in terms of a CrN (111) structural coefficient. (3) Vickers hardness is from Hv 1600 to Hv 2000.

Abstract: A steel product having a composition which contains by mass C: 0.01 to 1.9%, Si: 0.01 to 1.9%, Mn: 5.0 to 24.0% with balance consisting of Fe and unavoidable impurities and a steel product described above which further contains Cr: 18.0% or below and/or Ni: 12.0% or below in addition to the above essential elements. The above steel products may each further contain Al: 1% or below and/or N: 0.3% or below and the above steel products may each further contain one or more elements selected from among Nb, Ti, Zr, Mo and Cu in a total amount of 4.0% or below. The steel products can sufficiently follow the thermal expansion of a cylinder made of an aluminum alloy and thus enables the production of a piston ring which is suitable for use as a piston ring to slide on the inner face of a cylinder bore made of an aluminum alloy in an internal combustion engine and which can retain excellent sealing properties.

Abstract: In order to avoid burn traces on piston rings, it is proposed to provide the piston ring with a wear-protection coating which consists of a material with a thermal conductivity of at least 180 W/(m.K). At least 5% vol. of the wear-protection coating consists of aluminum nitride.