DE10212299B4 - Method for applying thermal spray coatings on galvanically coated piston rings and a piston ring produced by the method - Google Patents

Abstract

method for producing a piston ring (1) for the piston of a combustion machine with a protective layer, wherein the protective layer of a galvanic deposited hard chrome layer (2, 2 ') and a deposited thereon galvanized layer (4, 4 ') with lower hardness than the hard chrome layer (2, 2 ') characterized in that the galvanic layer (4, 4 ') acts as an intermediate layer and at least one further, sprayed layer produced by a thermal spray process (5, 5 ') with a higher melting point and / or higher Hardness as the intermediate layer (4, 4 ') is applied.

Description

The invention relates to a method for producing a piston ring for the piston of an internal combustion engine with a protective layer, wherein the protective layer consists of an electrodeposited hard chromium layer (US Pat. 2 . 2 ' ) and a galvanic covering layer deposited thereon ( 4 . 4 ' ) is formed, wherein the cover layer ( 4 . 4 ' ) a lower hardness than the hard chrome layer ( 2 . 2 ' ) and in particular consists of tin or copper, and a piston ring produced by the method.

In Many technical applications have a need to counter components Protect tribological effects to minimize their wear. In particular, in the system piston, piston ring and cylinder liner the wear plays one significant role. It is common practice for these system components with wear protection layers to provide. Possible Coatings are the deposition of galvanic layers or thermal spraying.

The DE 38 13 617 C1 discloses a plated chromium layer on a piston ring that is electrochemically or mechanically roughened. The rough layer is covered with a copper or tin layer. A spray coat is not provided.

The DE 17 51 573 C3 discloses a sprayed coating applied to a chrome layer. The chromium layer is roughened chemically or mechanically, an intermediate layer is not provided.

The GB 1 083 003 discloses a sliding bearing whose body is sprayed with lead or aluminum, a hard chrome plating layer is not provided.

In the DE 197 45 811 A1 is a generic galvanic hard chrome layer, which is used on tribologically stressed components in internal combustion engines, described. This is a galvanic hard chrome layer with a partially or through the entire layer thickness extending, by anodic circuit expanded crack network, embedded in the cracks solid particles, the hard chrome layer consists of at least two layers of hard chrome and the layers have a different crystallization form. With this layer, the running surfaces of piston rings for internal combustion engines were coated and the piston rings were examined in test runs. The coated piston rings showed high durability even under extreme temperature and wear conditions.

That applied to the galvanic hard chrome layer more layers can be can not be found in the publication.

The order of a further layer as a cover layer on a galvanically deposited hard chrome layer describes the DE 197 52 720 C2 , To produce this composite layer, a wear-resistant electroplated hard chrome layer is first deposited on the outer peripheral surface of the component and then a further galvanic top layer is applied, the cover layer being at least partially removed again. An object of the cover layer is to prevent the breaking away of the solid lubricant particles embedded in the hard chrome layer. The cover layer is formed of metals selected from a group consisting of copper, tin, nickel, chromium and alloys of these metals. If, for example, a further chromium layer is deposited as the cover layer and the galvanic hard chrome layer has no ceramic particles, then the cover layer need not be completely removed. The cover layer then also serves as a wear layer.

That on the cover layer, which consists for example of tin or copper, another layer can be applied, leaving the topcoat as Intermediate layer and thus acts as a bonding layer, the document not be removed. The primary task of the top layer is therein, a breaking out of the solid particles from the hard chrome layer to prevent.

One Disadvantage of the chrome layers is their high hardness, the run-in behavior influence negatively. So produce piston rings that with a chrome layer are provided on the cylinder surface as a counter partner no fast enema because they wear out very slowly. In particular it can by the high hardness the chrome layer even to increased wear on the friction partner come.

Another way to protect components that are subject to tribological wear, the application of thermal spray coatings. In the EP 0 931 172 B1 a piston ring is described for an internal combustion engine, on its tread is a 50 to 400 micron thick, wear-resistant layer, which is applied by means of a thermal spraying process. This layer is characterized in that a plurality of cubic, and / or titanium, a second metal and carbon-containing hard material phases and a metallic binder phase are present. As spraying These are called plasma spraying in the air or high-speed flame spraying.

Lots Although such thermal spray coatings can be a good run-in behavior guarantee, But they are the high standards, especially in terms of Long-term wear characteristics, grown only conditionally in modern internal combustion engines.

A base material for thermally sprayed layers is molybdenum, which is usually applied by means of flame spraying. The patent US Pat. No. 3,837,817 describes by way of example a technical solution to improve the properties of thermally sprayed molybdenum layers on piston rings. For this purpose, a self-fluxing alloy and a third component, which may be a carbide or oxide, mechanically mixed and sprayed.

Although molybdenum allows good run-in behavior does not have good wear properties, so that after abrasion of this layer of low wear resistant base material the piston ring is present on the mating surface.

In order to achieve a good intake behavior, is in the EP 0 900 326 B1 proposed to apply to the cylinder elements, such as cylinder liner, piston, piston skirt or piston ring for a diesel engine, a layer or a laminate of aluminum-bronze. In this case, the cylinder element is provided with at least two thermally sprayed, consisting of aluminum-bronze coating layers, of which the outer layer forms an inlet layer and the underlying layer a support layer whose average hardness is greater than the hardness of the inlet layer. The layer composite can be formed from two to seven coating layers of aluminum bronze with mutually differing properties.

Although the thermally deposited coating has a good run-in behavior, but after the break-in phase of the base material is present as a sliding partner, the base material may possibly trigger a strong counter-wear. That in the EP 0 900 326 B1 The coatings described can be applied to other wear protection layers, in particular hard chrome layers, can not be found in the publication.

task The invention is a method for producing wear protection layers to develop on piston rings, being a permanent and solid Connection between a hard chrome layer and a thermal Sprayed layer allows so as to be the positive wear characteristics of galvanic Hard chromium layers with the positive properties of thermal spray coatings too combine.

These The object is achieved by the characterizing part of claim 1 solved, advantageous developments and embodiments of the invention are documented in the subclaims.

It It is also an object of the invention to provide a piston ring, its galvanic coating allows a thermal sprayed coating to apply so as to improve the run-in behavior.

These The object is solved by the features of subclaim 8.

Of the inventive idea overcomes the aforementioned technical disadvantages in that on the hard chrome layer a galvanic cover layer is deposited and then a additional, produced by a thermal spray process inlet layer is applied, so that the cover layer acts as an intermediate layer. By the idea of the invention is it possible now the positive wear characteristics the galvanic hard chrome layer with the good run-in behavior to combine the sprayed layers.

The Adhesion between the sprayed layer and the intermediate layer results essentially of several different mechanical mechanisms and a chemical bond, which in their sum an excellent Enable connection. According to the invention Intermediate layer, which preferably consists of tin or copper, designed so that they have a lower melting point than the having thermal sprayed layer. Now reach the means of thermal spray process heated material particles the sprayed layer so the intermediate layer is locally melted and the particles dig into the intermediate layer. Here it comes, after the To cool off, to a mechanical bracing, the first one represents mechanical adhesion mechanism.

Another feature of the intermediate layer is that the intermediate layer has a lower hardness than the hard chrome layer. During all thermal spraying processes, the material particles of the coating material undergo an acceleration during the coating, so that together with their mass they impart an impulse to the intermediate layer. However, since the intermediate layer according to the invention has a lower hardness than the hard chrome layer, only the intermediate layer becomes mechanically broken, so that the material particles another way of bracing with the intermediate layer is given.

There the material of the intermediate layer at the same time a lower hardness than has the thermal spray coating, the intermediate layer gives way to the Spray material made, so that the intermediate layer, the particles of the Partially enclose spray material. The sprayed layer is thus anchored in the intermediate layer. A mechanism of mechanical Liability further increases and thus also a part of the liability mechanisms represents.

One An essential part of the invention is the Werkstosffkombination, it is proposed according to the invention to form the thermal sprayed layer of an aluminum-copper-based alloy. Since the intermediate layer is preferably formed of tin, is the possibility the mixed crystal formation is given at the interface. Thus stands the Material is a chemical bond available that the adhesion mechanism significantly supported.

Consequently is according to the method described in the invention a possibility given to bind the thermal sprayed layer to the intermediate layer, without the galvanic hard chrome layer is attacked. The Interlayer is electrodeposited on the hard chrome layer, so that too at this interface ensures an optimal connection is.

The Intermediate layer according to the invention with a layer thickness of up to 100 μm deposited. In a preferred embodiment of the invention the layer thickness at 20 microns and in a more preferred form at 10 microns.

To the application of the intermediate layer may transport or environmental influences the adhesion mechanisms of the sprayed layer on the intermediate layer deteriorate. It is thus proposed according to the invention, the intermediate layer clean before applying the spray coat. This can be special by means of an etching or flushing respectively.

In a further embodiment the invention is proposed, the thermal sprayed layer to form a copper-aluminum-based alloy. It has become in the experiments alloys of copper with an aluminum content up to a maximum of 12% by weight and up to 2% by weight of iron are particularly advantageous exposed.

Around to use the positive inlet properties of molybdenum is proposed according to the invention, to form the thermal sprayed layer of a molybdenum-based alloy.

Of the thermal sprayed layer as outer cover layer the protective layer can doing different tasks.

she can serve as a running-in layer and so the friction partners against excessive wear during the Protect inlet. The protective layer can also be next to the hard chrome layer as additional wear protection layer Serve and so increase the life of the components. It exists but also the possibility a biocompatible functional layer as a thermal spray coating apply, so that the surface for example, an area a metallic prosthetic implant forms.

When Procedures can Any thermal spraying methods are used are so according to the invention and in Particular mention of the wire and powder-promoting spraying. But it is also conceivable, the layer by means of other spraying, such as plasma, flame or high velocity flame spraying, to create. It is also conceivable here several spray layers on top of each other to arrange. It can but also any other layers on the thermal sprayed layer to be ordered.

The Thermal spray coating is doing with a layer thickness of up to 1000 μm applied and should not fall below a layer thickness of 20 microns. When preferred embodiment Layer thicknesses between 20 and 250 microns, and more preferably between 80 and 200 μm sought.

The inventive method is shown below on the basis of images from the test series and further in the next explained. It shows:

1 the cross section through the surface of a component with a protective layer applied according to the invention

2 the cross section through the surface of a component with an inventively applied protective layer in the region of the intermediate layer

In 1 is the cross section through the surface, a coated component according to the invention in the form of a piston ring 1 represented. On the component 1 became a galvanic hard chrome layer 2 deposited. On the outer smooth surface 3 the galvanic hard chrome layer 2 is a cover layer as an intermediate layer 4 to recognize as a narrow, light stripe. The thermal sprayed coating 5 was doing on the interlayer 4 applied.

2 shows an enlarged detail out 1 in the area of the intermediate layer 4 ' , The intermediate layer 4 ' is between the hard chrome layer 2 ' and the thermal spray coating 5 ' arranged. The 2 shows very clearly the mechanical adhesion mechanisms between thermal spray coating 5 ' and intermediate layer 4 '' , The thermal sprayed coating 5 ' is almost up to the hard chrome layer 2 ' into the interlayer 4 ' penetrated 6 and dug into the interlayer 7 , Due to the different hardnesses of the individual materials, the thermal spray coating has 5 ' in the interlayer 4 ' anchored 8th , so that an optimal connection to the hard chrome layer 2 ' is guaranteed.

Claims (9)

Method for producing a piston ring ( 1 ) for the piston of a combustion machine with a protective layer, wherein the protective layer of a galvanically deposited hard chromium layer ( 2 . 2 ' ) and a galvanic layer deposited thereon ( 4 . 4 ' ) with lower hardness than the hard chrome layer ( 2 . 2 ' ) characterized in that the galvanic layer ( 4 . 4 ' ) acts as an intermediate layer and thereon at least one further sprayed layer produced by a thermal spraying process (US Pat. 5 . 5 ' ) with a higher melting point and / or higher hardness than the intermediate layer ( 4 . 4 ' ) is applied. Method according to claim 1, characterized in that the intermediate layer ( 4 . 4 ' ) consists in particular of tin or copper and has a layer thickness of up to 100 microns, preferably up to 20 microns and more preferably up to 10 microns. Method according to one of claims 1 and 2, characterized in that the piston ring ( 1 ) is cleaned in a further process step after the application of the intermediate layer, in particular etched or rinsed, is. Method according to one of claims 1 to 3, characterized in that the thermal spray coating ( 5 . 5 ' ) is formed of a copper-aluminum-based alloy, wherein the alloy is formed of copper with up to 12 wt .-% aluminum and up to 2 wt .-% iron. Method according to one of claims 1 to 3, characterized in that the thermal spray coating ( 5 ; 5 ' ) is formed of a molybdenum-based alloy. Method according to one of claims 1 to 5, characterized that the thermal spraying process used is a wire-conveying Method, preferably an arc spraying, or a pulver promoting Method, preferably a plasma spraying method. Method according to one of claims 1 and 6, characterized in that the thermal spray layer ( 5 . 5 ' ) is present with a layer thickness between 20 .mu.m up to 1000 .mu.m, but preferably between 20 .mu.m up to 250 .mu.m and even more preferably between 80 .mu.m up to 200 .mu.m. Piston ring for the piston of an internal combustion engine produced according to one of claims 1 to 7, characterized in that the piston ring ( 1 ) has a protective layer which consists of a first hard chromium electroplated layer ( 2 . 2 ' ), a second electrodeposited layer ( 4 . 4 ' ) lower hardness than the intermediate layer and at least one third thermal spray layer ( 5 . 5 ' ) consists. Piston ring according to claim 8, characterized the intermediate layer is preferably made of tin and copper.