DE102007038188B4 - Wear-resistant coated piston ring and method for its production - Google Patents

Abstract

A wear resistant coated piston ring having a surface comprising a structured hard chrome layer applied to the surface obtainable by a method of depositing chromium from an electrolyte on a piston ring, the electrolyte comprising (a) a Cr (VI) compound in an amount, corresponding to 50 g / l to 600 g / l of chromic anhydride, (b) 0.5 g / l to 10 g / l of sulfuric acid, and (c) 1 g / l to 20 g / l of aliphatic sulfonic acid having 1 to 6 carbon atoms and operating with a cathodic current efficiency of 12% or less, a chromium solid particle layer deposited on the patterned hard chromium layer and a PVD or CVD layer deposited thereon.

Description

The invention relates to a piston ring, on the surface of which a structured hard chrome layer, a chromium solid particle layer and above a PVD or CVD layer is applied and a method for its production.

Piston rings that are exposed to mechanical stress must have highly wear-resistant surfaces. To achieve a high level of wear resistance, piston rings, in particular their running surfaces, can be coated with wear protection layers in the form of electrodeposited hard chrome layers, since such hard chrome layers are characterized by high hardness and thus high wear resistance.

Known in the prior art embodiments of a hard chrome layer to improve the physical properties are described in WO 2004/050 960 A1 and the DE 10 2004 019 370 A1 As a special process measure, the composition of the electrolyte used in the production and the low current efficiency of less than 12% make it possible to obtain a highly wear-resistant hard chromium layer whose structure is cup-shaped and / or labyrinth-like and / or columnar.

To improve the physical properties of electrodeposited hard chrome layers, it is also known to store solid particles in the hard chrome layers.

In the EP 0 217 126 B1 galvanic hard chrome layers are described, which have a crack network extending through the layer thickness and in whose cracks solid particles are embedded.

Particularly advantageous physical properties can be achieved by diamond particles embedded in the cracks of an electrodeposited hard chrome layer and having a size in the range from 0.25 to 0.4 μm, as in US Pat WO 0 104 386 A1 and the EP 1 114 209 B1 described.

For machine parts which are exposed to high temperatures as well as wear due to friction, for example piston rings or cylinders of internal combustion engines, a high resistance to burn marks is desirable in addition to high wear resistance. The chromium solid particle layers, chromium-diamond layers and structured hard chrome layers described in the abovementioned prior art have high wear resistance, but the fire-barrier strength of these coatings still needs to be improved.

The present invention is therefore based on the object to provide a piston ring with a highly wear-resistant and highly fire-resistant coating and a method for its preparation.

• (a) eine Cr(VI)-Verbindung in einer Menge, die 50 g/l bis 600 g/l Chromsäureanhydrid entspricht,
• (b) 0,5 g/l bis 10 g/l Schwefelsäure, und
• (c) 1 g/l bis 20 g/l aliphatische Sulfonsäure mit 1 bis 6 Kohlenstoffatomen enthält und wobei mit einer kathodischen Stromausbeute von 12% oder weniger gearbeitet wird,

eine auf der strukturierten Hartchromschicht aufgebrachte Chrom-Feststoffpartikel-Schicht und eine darauf aufgebrachte PVD- oder CVD-Schicht.According to the invention, this object is achieved by a wear-resistant coated piston ring, comprising a surface
a structured hard chrome layer applied to the surface,
obtainable by a process in which chromium is deposited from an electrolyte onto a piston ring, wherein the electrolyte

• (a) a Cr (VI) compound in an amount corresponding to 50 g / l to 600 g / l of chromic anhydride,
• (b) 0.5 g / l to 10 g / l sulfuric acid, and
• (c) containing 1 g / l to 20 g / l of aliphatic sulfonic acid having 1 to 6 carbon atoms and operating with a cathodic current efficiency of 12% or less,

a chromium solid particle layer applied to the structured hard chromium layer and a PVD or CVD layer applied thereto.

Surprisingly, this at least three-ply coating has both excellent wear properties and excellent fire crack resistance.

The structured hard chromium layer applied to the piston ring and the method for the production thereof are disclosed in US Pat EP 1 565 596 B1 and the DE 10 2004 019 370 A1 described.

The structured hard chromium layer applied to the surface of the piston ring according to the invention has a cup-shaped and / or labyrinth-like and / or columnar structure due to the deposition conditions, namely the composition of the electrolyte and the cathodic current efficiency of 12% or less, and has, inter alia, excellent wear and sliding properties on. According to the invention, the PVD or CVD layer is applied in a layer thickness, so that after a certain period of use, in particular after the running-in phase, it has worn away so far that the underlying structured layer is revealed. In this way, after the removal of the upper PVD or CVD layer, the PVD or CVD material located in the valleys of the underlying structured layer remains, so that the surface then remains from the raised hard chrome layer and the remaining material in the valleys the applied PVD or CVD layer is formed. The hard chrome layer mainly ensures wear resistance and the material in the valleys, especially for the fire resistance.

The advantageous properties of the structured hard chromium layer, in particular its high resistance to wear and corrosion, are surprisingly retained in this way, and the material of the applied layer located in the depressions additionally improves the resistance to burn marks. The remaining in the wells material of the PVD or CVD layer then acts as a lubricant, which, however, unlike conventional lubricants in the structured hard chrome layer remains, thus providing a lasting improvement in the fire resistance while maintaining the wear resistance. Furthermore, as well as the emergency running properties of the coated piston ring are improved. These improved physical properties of the multilayer coating according to the invention are particularly advantageous for internal combustion engines, which must realize very high mileage, for example in vehicles of transport companies such as taxi companies or in truck engines, in which mileages of up to two million miles are desirable.

The wear-resistant coated piston rings according to the invention are used to counteract mechanical wear, in particular frictional wear.

The structured hard chrome layer is formed by electrolytic deposition from the above-mentioned electrolyte comprising components (a) to (c) on the surface of the piston ring. For the purposes of the present invention, the term "electrolyte" is understood as meaning aqueous solutions whose electrical conductivity is brought about by electrolytic dissociation into ions. Accordingly, the electrolyte in addition to the components (a) to (c) and optionally further present additives as the remainder of water.

The amounts of components (a) to (c) given above are based on the electrolyte. As component (a) preferably CrO _{3 is} used, which has proven to be particularly favorable for the electrolytic deposition of chromium. The aliphatic sulfonic acid preferably used as component (c) is methanesulfonic acid, ethanesulfonic acid, methanedisulfonic acid and / or ethanedisulfonic acid. Particularly preferred is methanesulfonic acid.

The electrolyte is substantially free of fluorides in a preferred embodiment. Here are understood as fluorides both simple and complex fluorides. The term "substantially no fluorides" means that so much fluoride is tolerable in the electrolyte that the formation of the patterned hard chromium layer is unaffected. The amount of fluorides that are tolerable can be readily determined by those skilled in the art. It has proved to be favorable if not more than 0.1 g / l fluoride is present in the electrolyte.

The electrolyte may further contain conventional catalysts which aid in the deposition of chromium, for example sulfate ions (SO ₄ ^2- ) and / or chloride ions (Cl ^- ). These may be present in conventional amounts in the electrolyte.

In a further preferred embodiment, the electrolyte may contain as additional component 10 g / l to 200 g / l of at least one dense cathode film forming compound selected from ammonium molybdate, alkali molybdate, alkaline earth molybdate, ammonium vanadate, alkali metal vanadate, alkaline earth metal alkane, ammonium zirconate, alkali zirconate and alkaline earth zirconate. As alkali ions Li ⁺ , Na ⁺ and K ⁺ can be used. Examples of alkaline earth ions are Mg ²⁺ and Ca ²⁺ . The said component forms a dense cathode film during electrolytic deposition, as in US Pat EP 1 565 596 B1 described. In a particularly preferred embodiment, the component (NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O, which is particularly favorable for the formation of the patterned hard chrome layer.

Further, it is preferable that the Cr (VI) compound is CrO ₃ . The aliphatic sulfonic acid is preferably methanesulfonic acid.

To form the structured hard chrome layer on the piston ring, it is switched cathodically and immersed in the electrolyte. To the piston ring, a direct current, for example, a pulsating direct current with a frequency up to 1000 Hz, applied. The temperature for the deposition of the chromium may be 45 ° C to 95 ° C, especially about 50-60 ° C. The duration of the deposition is chosen as a function of the desired thickness of the structured hard chromium layer, the layer becoming thicker the longer the deposition takes place. The structured hard chrome layer preferably has a layer thickness of 30-70 μm. The average height of the elevations in the surface of the structured hard chrome layer is preferably 5-40 μm, more preferably 10-30 μm.

In a preferred embodiment, a current density of 20 A / dm ² to 200 A / dm ² is used. As a result, particularly favorable structures of the hard chrome layer are obtained. The higher the current density is chosen, the denser the protruding areas of the patterned hard chrome layer.

In an electrolytic deposition regularly only a portion of the amount of electricity used in the metal deposition, the rest of the amount of electricity leads to losses, primarily hydrogen is generated. The cathodic current efficiency, also referred to as efficiency, is the ratio of the amount of current that leads to the deposition of metal to the amount of electricity used. If, for example, 100 Ah are used, of which 25 Ah lead to metal deposition and 75 Ah losses are present, the cathodic current efficiency is 25%. The cathodic current efficiency in the production of the structured hard chromium layer according to the method of the invention is 12% or less. If the current efficiency is higher, the desired structuring of the hard chrome layer is not obtained.

The structured hard chrome layer obtainable by the method described above is - in contrast to conventional hard chrome layers, which have a spherical surface structure - cup-shaped and / or labyrinth-like and / or columnar and has proven to be particularly resistant to wear and corrosion.

In the context of the invention, a layer applied to a surface or a layer is understood as meaning both a layer applied directly to the surface or the layer and a layer applied to an intermediate layer. A layer C applied to a layer A is thus present both in a layer structure A, C and in a layer structure A, B, C, where B is the intermediate layer.

In the context of the invention, a PVD layer is understood to mean a layer deposited on a piston ring by PVD (Physical Vapor Deposition). PVD processes are known per se to the person skilled in the art. The layer starting material is vaporized by laser, ion or electron beams or by arc discharge, usually under reduced pressure at about 1-1000 Pa, and the PVD layer formed by condensation of the material vapor on the substrate. If necessary, a suitable process gas can be supplied.

For the purposes of the invention, a CVD layer is understood as meaning a layer deposited on a piston ring by CVD (Chemical Vapor Deposition). CVD methods are known per se to the person skilled in the art. In a CVD process, a gaseous phase solid is deposited on the heated surface of a substrate by a chemical reaction. In general, CVD processes are also carried out under reduced pressure at about 1-1000 Pa.

As PVD or CVD layers, all coatings obtainable by PVD or CVD processes are suitable according to the invention. The PVD or CVD layers preferably comprise titanium nitride compounds or chromium nitride compounds, in particular titanium nitrides of the formula TiN _x , titanium nitride compounds of the formula TiN _x A _y , chromium nitrides of the formula CrN _x and chromium nitride compounds of the formula CrN _x A _y , where A is carbon (C), Boron (B), oxygen (O) and / or hard-forming elements such as silicon (Si), vanadium (V), niobium (Nb), tungsten (W), aluminum (Al), tantalum (Ta), zirconium (Zr ), etc., and x and y are independently from 0.1 to 1.5. X and y are independently of each other 0.3-1.2, particularly preferably 0.5 to 1. For example, titanium nitride (TiN _x ), titanium carbonitride (TiC _y N _x ), titanium oxide nitride (TiO _y N _x ), titanium aluminum nitride ( TiAl _y N _x), chromium nitride (CrN _x), chromium carbonitride (CrC _y N _x), chromium oxide nitride (CrO _y N _x), Chromaluminiumnitrid (CrAl _y N _x) or multi-element compounds such as Chromaluminiumsiliciumnitride, Chromaluminiumzirkoniumnitride or Chromaluminiumsiliciumzirkoniumnitride use, in particular those of the formulas CrAl _a Si _b N _x , CrAl _a Zr _b N _x or CrAl _a Si _b Zr _c N _x , where a, b, c and x are each independently from 0.1 to 1.5, preferably 0.1- 1.2, more preferably 0.2-1. Particularly preferred in the multilayer arrangement according to the invention as the PVD or CVD layer chromium nitride compounds are used, which may contain the other elements specified above. Particularly preferably, the PVD or CVD layer consists of the abovementioned compounds.

The layer thickness of the PVD or CVD layer is preferably 5-80 μm, more preferably 5-60 μm, even more preferably 5-40 μm, and most preferably 10-30 μm. As the PVD or CVD layer is applied to a structured layer, for the purposes of the invention a PVD or CVD layer is also understood to mean a deposited PVD or CVD material which completely or partially covers the depressions of the underlying structured layer thereby completely covering or only partially covering the overlying structured layer or merely filling all or part of the recesses of the underlying structured layer without forming a continuous layer in the sense of complete coverage. The layer thickness in the latter case is the mean value of the height of the filling of the recesses.

Between the patterned hard chrome layer and the PVD or CVD layer is a chromium solid particle layer.

In such at least three-layer coatings, the chromium solid particle layer, which has a particularly high resistance to wear, takes on the cup-shaped and / or labyrinth-like and / or columnar structure of the underlying, d. H. The patterned hard chrome layer facing the piston ring at least partially and the PVD or CVD layer behaves as described above. This means that after a certain useful life of a correspondingly coated piston ring, the surface is essentially formed by the elevations of the chromium solid particle layer and the material of the PVD or CVD layer remaining in the depressions.

In this way, the particularly advantageous cup-shaped and / or labyrinth-like and / or columnar structure of the structured hard chromium layer is transferred to the chromium solid-particle layer, which is even more resistant to wear compared to the structured hard chromium layer. H. continued so to speak through the chrome solid particle layer, and so the very high wear resistance of the chromium solid particle layer combined with the advantageous structure of the structured hard chrome layer. In addition, at the same time the fire resistance is permanently improved by the PVD or CVD layer. The remaining in the wells PVD or CVD material also increases the sliding properties, since it acts as a lubricant.

The chromium solid particle layer arranged according to this multilayer coating according to the invention between the structured hard chromium layer and the PVD or CVD layer is, for example, in US Pat EP 0 217 126 B1 and the EP 1 114 209 B1 described.

The chromium solid particle layer of the coating according to the invention comprises a crack network in which solid particles are embedded. The gap width of the cracks should be greater than the particle size and is preferably above 0.3 μm, in particular above 0.5 μm. Hard particles of tungsten carbide, chromium carbide, aluminum oxide, silicon carbide, silicon nitride, boron carbide and / or diamond are preferably used as solid particles. The grain size of the solid particles is preferably in the range of 0.1 to 5 microns. Diamonds are particularly preferred as solid particles, and below this, in turn, those having a size in the range of 0.25-0.4 μm are preferred. Further, alumina particles having a particle size in the range of about 0.1-5 microns are preferred. Embedded diamond particles can be formed from mono- and / or polycrystalline diamond. With polycrystalline diamond, the better results are often achieved because a polycrystalline diamond has many slip planes due to the many different crystals. The solid particles or hard material particles can also be a mixture of solid particles of different types of substances in combination.

Advantageously, solid lubricant particles, solid particles for increasing the ductility and / or the corrosion resistance may be contained in the cracks in the chromium solid particle layer. By incorporating additional particles in addition to the hard material particles, the layer can still be adapted for the respective application. For example, as solid lubricant particles, hexagonal boron nitride, graphite and / or polymer particles, in particular of polyethylene and / or polytetrafluoroethylene, can additionally be introduced into the cracks. To increase the ductility, ductile metals or metal alloys of tin, titanium or aluminum may be incorporated.

For the preparation of the chromium solid particle layer, known chromium plating baths with dispersed fatty particles are used, as known from the prior art. During chrome plating, the piston ring to be chromed is first cathodically connected to form a microcracked hard chrome layer, then the piston ring is anodically connected so that the microcracks expand to the desired gap width and the cracks fill with the solid particles.

For the purposes of the invention, a structured hard chrome layer and a chromium solid particle layer not only mean layers of pure chromium and possibly solid particles, but also layers of chromium alloys, in particular molybdenum, vanadium and / or tungsten. The invention thus also relates to wear-resistant coated piston rings which comprise a structured chromium alloy layer and additionally a chromium alloy solid particle layer, with a PVD or CVD layer being applied over it. If the structured hard chromium layer and / or chromium solid particle layer is not formed of pure chromium but of an alloy, the alloying elements in the chromium plating electrolyte are dissolved as salts and galvanically deposited together with the chromium in the form of a chromium alloy. In this case, the alloying elements are preferably present in amounts of from 0.1 to 30 percent by weight in the chromium layer. Such layers are even more wear-resistant and ductile than pure chrome layers.

The thickness of the electroplated chromium solid particle layer should preferably be several times greater than the particle size of the particles. This is desirable so that the particles can be completely incorporated into the crack network formed in the hard chrome layer and not only individual particles are only partially embedded in the chromium layer.

The layer thickness of the chromium solid particle layer is further selected according to the invention so that the structure of the underlying structured hard chromium layer in the chromium solid particle layer is at least partially reflected, d. H. the chromium solid particle layer has an at least partially cup-shaped and / or labyrinth-like and / or columnar structure. It has proved to be advantageous if the layer thickness of the chromium solid particle layer does not exceed five times the average depth of the depressions in the structured hard chrome layer. The layer thickness of the chromium solid particle layer is preferably in the range of 20-800 μm, more preferably 30-500 μm and even more preferably 50-300 μm.

The chromium solid particle layer itself may consist of several layers which are applied one after the other. If several layers are applied and the particles are respectively introduced into the cracks of the individual layers, a coating can be achieved which has a better distribution of the solid particles in the coating both in their entire thickness and over their surface, since the cracks not always formed in the same places.

If the chromium solid particle layer consists of at least two layers, the individual layers may have different levels of high or completely different alloy constituents. This can be suitably selected depending on the requirements of the layer or on the piston ring to be coated.

If the chromium solid particle layer is formed such that the at least two chromium layer layers have a different crystal structure, the strength properties of the layer can be improved even further. In this case, to produce at least one hard chromium layer, the chromium is deposited from the electrolyte on the cathode-connected piston ring with pulsating direct current with current densities between 5 and 250 A / dm ² , so that several layers of hard chromium with different crystallization form are deposited in the chromium layer according to the current density. After each deposition phase of a layer, the piston ring is anodically connected, so that the crack network expands in the hard chrome and fills with the solid particles. In this case, the layers of different crystal structure are preferably deposited one above the other alternately.

The proportion of the solid particles in the chromium solid particle layer is preferably 0.1 to 10 wt .-% in order to achieve a high wear resistance.

The above-described PVD or CVD layer is then applied to the chromium solid particle layer. The suitable, preferred and particularly preferred embodiments of the PVD and CVD layers described above are also suitable, preferred and particularly preferred when there is a chromium solid particle layer between the structured hard chrome layer and the at least one PVD or CVD layer.

1. A) Chrom aus einem Elektrolyten auf einen Kolbenring abgeschieden wird, der
   • (a) eine Cr(VI)-Verbindung in einer Menge, die 50 g/l bis 600 g/l Chromsäureanhydrid entspricht,
   • (b) 0,5 g/l bis 10 g/l Schwefelsäure, und
   • (c) 1 g/l bis 20 g/l aliphatische Sulfonsäure mit 1 bis 6 Kohlenstoffatomen, enthält, wobei mit einer kathodischen Stromausbeute von 12% oder weniger gearbeitet wird, anschließend
2. B) eine Chrom-Feststoffpartikel-Schicht durch elektrolytische Chromabscheidung in Gegenwart von Feststoffpartikeln aufgebracht wird und anschließend
3. C) mindestens eine CVD-Schicht durch chemische Gasphasenabscheidung und/oder eine PVD-Schicht durch physikalische Gasphasenabscheidung aufgebracht wird.

The invention further relates to a method for producing a wear-resistant and fire-resistant coated piston ring, comprising the steps of

1. A) Chromium is deposited from an electrolyte on a piston ring, the
   • (a) a Cr (VI) compound in an amount corresponding to 50 g / l to 600 g / l of chromic anhydride,
   • (b) 0.5 g / l to 10 g / l sulfuric acid, and
   • (c) 1 g / l to 20 g / l of aliphatic sulfonic acid having 1 to 6 carbon atoms, followed by working with a cathodic current efficiency of 12% or less, subsequently
2. B) a chromium solid particle layer by electrolytic chromium deposition in the presence of solid particles is applied and then
3. C) at least one CVD layer by chemical vapor deposition and / or a PVD layer by physical vapor deposition is applied.

In this method, the above-described suitable, preferred and particularly preferred embodiments of the invention are also suitable, preferred and particularly preferred. The method according to the invention has the advantages described above in connection with the wear-resistant coated piston ring. The layers applied to the piston ring may each comprise individual layers, for which steps (A) (B) and (C) are to be repeated under identical or changed conditions.

Furthermore, the invention relates to a wear-resistant coated piston ring, which is obtainable by the process according to the invention.

It is understood that the features mentioned above and those explained below can be used not only in the specified combinations, but also in other combinations or in isolation, without departing from the scope of the present invention.

The following examples illustrate the invention.

Example 1:

Production of a structured hard chrome layer

A chromium electrolyte of the following composition is prepared: Chromic anhydride CrO ₃ 250 g / l Sulfuric acid H ₂ SO ₄ 2.5 g / l methane 4 g / l.

A piston ring is introduced into the electrolyte after conventional pretreatment and coated at 55 ° C with 40 A / dm ² for 30 min.

The piston ring has a textured chromium layer after treatment. This chrome layer is shiny on the protruding surface areas (supporting portion) and in the recesses of the structure is brown-colored cathode film.

Coating with a chrome-diamond layer

• 250 g/l CrO₃ Chromsäure
• 1,5 g/l H₂SO₄ Schwefelsäure
• 10 g/l K₂SiF₆ Kaliumhexafluorosilikat

Subsequently, the piston ring coated with the structured hard chromium layer is immersed in a crack-forming electrolyte which contains the following constituents:

• 250 g / l CrO ₃ chromic acid
• 1.5 g / l H ₂ SO ₄ sulfuric acid
• 10 g / l K ₂ SiF ₆ potassium hexafluorosilicate

In it 50 g / l monocrystalline diamond particles are dispersed by stirring with an average particle size of 0.3 to 0.4 microns and held in suspension during chromium plating. The Chrome plating takes place at a temperature of 60 ° C. In this case, the piston ring to be chromed is first connected cathodically in a first stage and chromed for 8 minutes at a current density of 65 A / dm ³ . In a second stage is reversed and anodic circuit of the piston ring for one minute at a current density of 60 A / dm ^3, the crack network of the previously deposited chromium layer expanded and filled with diamond particles. This cycle, namely cathodic chrome plating for 8 minutes and anodic etching for 1 minute, is repeated a total of five times, resulting in a layer with a layer thickness of about 40 μm, which has a diamond content of 4% by weight of the entire layer.

Coating with a PVD-CrN layer

In the PVD process, a CrN layer with a layer thickness of about 30 μm is applied.

Example 2:

According to the above specification, a structured hard chrome layer was applied to a piston ring and then a PVD-CrN layer was applied directly to the structured hard chrome layer.

Example 3:

It was provided according to the above rule, a piston ring with a structured hard chrome layer and then also applied according to the above rule on this structured hard chrome layer, a chromium diamond particle layer.

Example 4:

A piston ring was provided according to the above rule with a structured hard chrome layer.

With the aid of a simulation test machine (firestop tester from Plint), the fire-resistance of the multilayer coatings according to the invention (Examples 1 and 2) with a structured hard chrome layer (Example 5), a two-layer coating of a structured hard chromium layer and a chromium diamond particle layer (Example 4) as well as a chromium diamond particle layer and a PVD layer (Example 3). For this purpose, the fire resistance of the piston rings of Examples 1 to 5 were measured after the running-in phase of the piston rings (use under engine conditions on an engine test bench, 15 h in a 6-cylinder turbodiesel engine under full load). Table: Fire resistance of coated piston rings coating Scuff resistance structured hard chrome layer 100% + Chrome diamond particle layer (Example 1) + PVD layer structured hard chrome layer 60% + PVD layer (Example 2) Chromium diamond particle layer 50% + PVD layer (Example 3) structured hard chrome layer 50% + Chrome diamond particle layer (Example 4) structured hard chrome layer 30% (Example 5)

As can be seen from the fire resistance given in the table above, the fire-resistance of the coatings according to the invention, in particular the three-layer coating consisting of a structured hard chromium layer, a chromium solid particle layer and a PVD layer compared to the coatings of the prior art is significantly improved , The wear resistance of the layers could be obtained.

Claims (8)

Wear-resistant coated piston ring, with a surface comprising a structured hard chrome layer applied to the surface, obtainable by a method in which chromium is deposited from an electrolyte on a piston ring, wherein the electrolyte (a) a Cr (VI) compound in an amount corresponding to 50 g / l to 600 g / l of chromic anhydride, (b) 0.5 g / l to 10 g / l sulfuric acid, and (c) containing 1 g / l to 20 g / l of aliphatic sulfonic acid having 1 to 6 carbon atoms and operating with a cathodic current efficiency of 12% or less, a chromium solid particle layer applied to the structured hard chromium layer and a PVD or CVD layer applied thereto. Piston ring after Claim 1 , characterized in that the Cr (VI) compound is CrO ₃ and / or the aliphatic sulfonic acid is methanesulfonic acid. Piston ring after Claim 1 or 2 , characterized in that the PVD or CVD layer comprises a chromium nitride compound. Piston ring after Claim 3 , characterized in that the chromium nitride compound is selected from the group chromium nitride, chromium oxide nitride and chromium carbonitride. Piston ring after one of Claims 1 to 4 , characterized in that the PVD or CVD layer has a layer thickness of 5 to 80 microns. Piston ring after one of Claims 1 to 5 , characterized in that the chromium solid particle layer is a hard chrome plating layer, wherein there are cracks in the layer and embedded in the cracks solid particles. Piston ring after one of Claims 1 to 6 , characterized in that the solid particles are hard material particles of tungsten carbide, chromium carbide, alumina, silicon carbide, silicon nitride, boron carbide and / or diamond. A method of making a wear resistant coated piston ring comprising the steps of A) Chromium is deposited from an electrolyte on a piston ring, the (a) a Cr (VI) compound in an amount corresponding to 50 g / l to 600 g / l of chromic anhydride, (b) 0.5 g / l to 10 g / l sulfuric acid, and (c) 1 g / l to 20 g / l of aliphatic sulfonic acid having 1 to 6 carbon atoms, followed by working with a cathodic current efficiency of 12% or less, subsequently B) a chromium solid particle layer by electrolytic chromium deposition in the presence of solid particles is applied and then C) at least one CVD layer by chemical vapor deposition and / or a PVD layer by physical vapor deposition is applied.