DE102007050811A1 - Wear protection layer and method for its production - Google Patents

Abstract

The invention relates to a wear protection layer for a frictionally stressed component, comprising a hard chrome layer. On the hard chrome layer, a layer of a polysiloxane is applied. Furthermore, the invention relates to a method for applying the wear protection layer. For this purpose, the component is first coated with a hard chrome layer. Finally, a polysiloxane layer is applied to the hard chrome layer.

Description

State of the art

The The invention is based on a wear protection layer for a frictionally stressed component comprising a hard chrome layer, and a method for producing the wear protection layer.

To the Protection against wear, for example, is applied galvanically Chrome layers in many areas of mechanical and apparatus engineering used. For example, for valve components, for example, in injection valves, in particular high-pressure injection valves, Hard chrome layers known as wear protection. These especially as a protective layer under impact used.

In particular, when using the wear protection layer in auto-igniting internal combustion engines with high-pressure injection, which are generally injection pressures in the range of 1500 to 1800 bar, which can be further increased in future developments, these hard chrome layers, however, to the limits of resilience. In particular, the comparatively high coefficient of friction of hard chrome compared to steel of μ = 0.2 is increasingly negatively noticeable. This is due to a superimposed oscillating movement of the component partners, for example armature and armature nozzle or nozzle needle and nozzle body, which increases with increasing component load and thereby initiates an abrasive removal of layer particles. The released layer particles lead to accelerated damage to the protective layer system. In addition, under the high loads of injection components in the internal combustion engines, an adhesive wear, through which also layer components are broken out of the composite and thus further promote the wear of the layer. As a remedy, it is for example DE-A 197 45 811 known, the protective layers micro- or nanoparticles with lubricating effect, eg. As PTFE, graphite, hexagonal boron nitride or molybdenum disulfide. The incorporation of the particles is generally carried out in microcracks in the hard chrome layer.

at Frictional stress, the micro- or nanoparticles with intrinsic lubricating action exposed and thus act lubricating. This technique of incorporation of lubricating particulates becomes particular widely used in nickel coatings. For chrome layers Although the technology is described, it is almost unavailable on the market. This is due to the fact that the chromium plating electrolyte generally very acidic and highly oxidizing. For this reason, organic additives are the shortest Time oxidatively decomposed. The organic additives, in general Surfactants, however, are necessary to allow particles in the electrolyte be present suspended and then in the electrocrystallization with to be built in. Without such surfactant additives leaves the particle storage almost do not perform.

moreover can be in thin chrome layers, for example less than 10 μm only particles less than 1 μm be stored in order not to weaken the supporting chromium matrix. However, especially at very low pH, smaller ones result Particles for increased agglomeration and formation of agglomerates which partly larger than 10 microns are. This leads to a violation of Integrity of the chrome layer. Also capsules, the lubricants can be contained and stored in general significantly larger than 1 μm.

Also the likewise known melting of polytetrafluoroethylene powders on chrome layers only works on easily accessible Areas. For internal geometries or the coating of holes is the method can not be used or it leads to very uneven Layer distributions.

Disclosure of the invention

Advantages of the invention

A Wear protection layer formed according to the invention For a frictionally stressed component or vibration superimposed Impact stress includes a hard chrome layer, wherein on the hard chrome layer a layer of a polysiloxane is applied.

By the layer of polysiloxane applied to the hard chrome layer becomes an improvement of the wear tendency of the hard chrome layer achieved. So it is possible, for example, opposite a hard chrome layer that does not matter with another layer a polysiloxane is provided, the wear resistance by a factor of 4 with respect to the weight loss and the Factor 10 with respect to the wear volume increase.

Under Weight loss is the mass of coating material to understand which is removed by wear from the coating. Accordingly, the volume becomes under wear volume Coating material understood that removed by the wear becomes. An improvement in terms of weight loss or the Wear volume means that the weight loss or the wear volume is reduced.

In a preferred embodiment, the hard chrome layer a layer thickness in the range of 2 to 20 microns, preferably in the range of 5 to 15 microns and in particular approximately 10 microns and the layer of polysiloxane one layer thickness in the range of 0.1 to 2 μm, preferably in the range of 0.2 to 0.8 microns and in particular of about 0.5 microns on.

By the order of the polysiloxane layer on the hard chrome layer is the adhesion tendency of the hard chrome layer by change achieved the chrome layer topography and in the further course of wear through Achieved formation of the so-called 3rd body.

The Polysiloxane is preferably a compound of optionally perfluorinated or partially fluorinated siloxanes.

wobei R¹, R², R³, R⁴, R⁵, R⁶ jeweils unabhängig voneinander -CF₃, -OCF₃, -O-SiR¹R²R⁵, O-Si(CF₃)₃, ein lineares oder verzweigtes C₁- bis C₁₅-Alkyl, eine Vinyl-, Epoxy-, Methacryloxy-, Amino- oder Arylverbindung, oder -O-M-OR, wobei M ein Metallatom, vorzugsweise ausgewählt aus Ti, Al und Zr, und R ein C₁- bis C₃-Alkyl oder Wasserstoff bedeuten, und
R⁷, R⁸, R⁹, R¹⁰ jeweils unabhängig voneinander Wasserstoff oder Fluor bedeuten, wobei in den Resten R¹ bis R⁶ enthaltener Wasserstoff teilweise oder vollständig durch Fluor substituiert sein kann.The optionally perfluorinated or partially fluorinated siloxanes are preferably selected from

wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ^{6 are} each independently of one another -CF ₃ , -OCF ₃ , -O-SiR ¹ R ² R ⁵ , O-Si (CF ₃ ) ₃ , a linear or branched C ₁ to C ₁₅ alkyl, a vinyl, epoxy, methacryloxy, amino or aryl compound, or -OM-OR, wherein M is a metal atom, preferably selected from Ti, Al and Zr, and R is a C ₁ - to C ₃ alkyl or hydrogen, and
R ⁷ , R ⁸ , R ⁹ , R ¹⁰ each independently represent hydrogen or fluorine, wherein hydrogen contained in the radicals R ¹ to R ⁶ may be partially or completely substituted by fluorine.

With particular preference the siloxanes are selected from

• – Beschichten eines Bauteiles mit einer Hartchromschicht,
• – Aufbringen einer Polysiloxanschicht auf die Hartchromschicht.

The invention further relates to a method for producing the wear protection layer, which comprises the following steps:

• Coating a component with a hard chrome layer,
• - Applying a polysiloxane on the hard chrome layer.

The coating of the component with the hard chrome layer is generally carried out by a galvanic coating process. The coating process can be carried out in any manner known to those skilled in the art. Usually, a sulfuric acid chromium electrolyte with addition of dimethanesulfonic acid is used as the catalyst. To coat the component with the hard chrome layer, the component is usually first cleaned, for example, to remove fats from the surface so that the chromium layer holds firmly on the component. The purification step is generally carried out at a temperature in the range of 20 to 70 ° C for 60 to 300 seconds. After the cleaning step, a rinsing step is generally carried out with demineralized water. After rinsing, the component is first subjected to activation by electroless plating in a bath containing the chromium electrolyte at a temperature of about 60 ° C for a period of about 60 s. Subsequently, the chrome layer is applied by electroplating. For the galvanic coating, the component is first roughened in a chrome bath. This is carried out anodically at a current of 10 to 200 A / dm ² for a period of generally 30 s and at a temperature of about 60 ° C. Subsequently, the component is galvanically ver in chrome bath ver chrome plated. This is also done anodically at a current of 10 to 200 A / dm ² for a period of 600 s at a temperature in the range of 60 ° C. For example, Ankor 1126 from Enthone GmbH is used as the chrome bath. After coating, a rinsing step is usually carried out with demineralized water at a temperature of 90.degree. Finally, the thus coated component is dried. For this purpose, the component is generally exposed to a circulating air drying at a temperature in the range of 100 ° C for a period of about 30 min.

According to the invention on the hard chrome layer in a next step the Polysiloxane applied. For this purpose, preferably first a dissolved in a solvent siloxane by applied a dipping process or a spraying process.

The Siloxane is preferably as already described above perfluorinated or partially fluorinated siloxane.

The Solvent in which the siloxane is dissolved is for example, an alcohol, preferably selected from isopropanol, Butanol, ethanol, ethylhexanol, methoxypropanol, or even for example Acetone, ethyl acetate, xylene or water.

The Ratio of siloxane to solvent is preferably in the range of 1:10 to 10: 1.

To the Applying the polysiloxane layer is the component preferably cleaned in a first step and then with rinsed with demineralized water. As a result, where appropriate when applying the hard chrome layer resulting impurities away.

The Cleaning is usually done by wetting the component with a weak alkaline cleaner. The wetting takes place for Example by dipping or by means of a spraying technique. Usually used weakly alkaline cleaners are, for example, commercially available Products containing potassium hydroxide or sodium hydroxide with added surfactant contain. A suitable cleaner is, for example, Slotoclean AK-FSA the Dr.-Ing. Max Schlötter GmbH & Co.KG in 1 to 2% solution. If the wetting of the component is done by dipping, then this will preferably for about 60 s at a temperature of about 70 ° C immersed in the cleaner. So that the chrome surface of the component is loaded with hydroxyl groups, is the alkalinity of the cleaner requirement. At the hydroxyl-loaded Sites binds the siloxane by hydroxylation reaction. alternative however, plasma activation is also possible.

To cleaning the component is blown off with the hard chrome layer. As a result, the component is dried. The blowing takes place with inert gases that are highly pure and oil-free. This is necessary to prevent contamination of the surfaces with oil residues is avoided. Suitable gases are, for example, highly pure and oil-free Nitrogen or high-purity or oil-free air.

To The blowing off is done by spraying or dipping the in Solvent dissolved siloxane applied. in the Following the application of the siloxane is again blowing off with a high-purity and oil-free gas. By blowing off with highly pure and oil-free gas is an optionally resulting excess of siloxane, which in the application arises, discharged again from the component. The paint surplus arises, for example, when the siloxane on the components or into the interior of, for example, injector valves by flushing, Dipping or spraying techniques is applied. In the application may form a 5 to 50 microns thicker Paint film off. If this paint film directly crosslinked or cured becomes embrittlement with inadequate Paint adhesion and paint stability. To avoid this will be the paint surplus, which arises during application, from the component discharged.

To the blow-off of the component with high-purity and oil-free Gas, for example nitrogen or air, face layer thicknesses of the siloxane varnish in the range of 0.1 to 2 microns. alternative To blow off with the high-purity and oil-free gas can excess Paint can also be thrown off.

Finally the siloxane is cured to the polysiloxane layer. The curing takes place at a temperature in the range of 120 to 350 ° C for a time in the range of 15 up to 60 minutes.

Brief description of the drawings

One Embodiment of the invention is in the drawing shown and in the following description in more detail explained.

The single figure shows a representation of a nozzle body for an injection valve

Embodiments of the invention

In the only figure is a nozzle body for an injection valve shown.

A nozzle body 1 includes a hole 3 in which an injection valve member, not shown here, is guided. With the injection valve member is an injection port 5 closed or released. To close the injection opening 5 the injection valve member is in a valve seat 7 posed.

The nozzle body is first chrome plated with a hard chrome layer. After chrome plating, cleaning is carried out in a weakly alkaline cleaner. The cleaning is generally carried out at a temperature in the range of 20 to 90 ° C for a period of 10 to 300 s. To remove the residues of the cleaner is then followed by a rinse in demineralized water for preferably 10 to 300 s. By blowing off with a high-purity and oil-free inert gas, preferably with nitrogen, the surface of the nozzle body 1 dried residue-free. After drying the surface, a silane coating is performed. The coating is carried out, for example, with Silan H5099 or H5098 from FEW.

To the nozzle body 1 To coat with silane, siloxane is diluted by means of a water or solvent mixture in the ratio of siloxane to solvent in the range of 1:10 to 10: 1. Thereafter, the nozzle body 1 immersed for 10 to 60 s at room temperature in the siloxane / solvent mixture. Alternatively, it is also possible, the nozzle body 1 by spraying with the siloxane / solvent mixture to wet. A uniform coating is achieved in this case by several successive spraying steps. After application of the solvent-siloxane mixture, the nozzle body 1 blown off with a high-purity and oil-free inert gas. Nitrogen is particularly suitable as the gas. By blowing off excess siloxane / solvent mixture is removed. In addition, it serves for venting with simultaneous escape of the solvent.

To the blow-off is cured by networking the Polymer chains by elimination of water or alcohol groups. The mechanical properties of the polysiloxane coating produced thereby, that means hardness and abrasion, are dependent from the curing process. The thermal curing is generally at least for at least 30 min 100 ° C performed. A maximum layer hardness the polysiloxane layer is at temperatures above 150 ° C. achieved.

In addition to the nozzle body shown here 1 For example, the layer according to the invention can also be used with any other component that is subjected to wear.

example

to Testing the coating according to the invention Wear measurements were made with a pin-and-disk tribometer carried out as a model test bench. For this was a coating according to the invention on a round disc with 25 mm diameter and a thickness of 8 mm made of 100 Cr6 steel applied. For comparison, a disk with a hard chrome layer coated as known in the art.

Of the Wear path was 250 m with a wear force of 10 N. The wear radius was 6 mm. As a counter body a tungsten carbide ball with a diameter of 6 mm was used. The test was carried out at room temperature and a relative Humidity of 24 to 30% performed.

Out a mass determination of the coated disks before and after Wear test was the one caused by fretting Mass loss determined. In addition, the profile of the friction track was confocal White light microscopy with a μ-surf device determined by the company Nanofocus. With the geometric wear radius the wear volume could be calculated.

Of the Comparison of Friction Wear Results of Hard Chrome Coating, as known from the prior art, to that with a Polysiloxane layer modified hard chrome layer shows that through the application of the polysiloxane layer the mass loss by at least 70% is reduced and the wear volume is at least 90% reduced.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 19745811 A [0003]

Claims (13)

Wear protection layer for a frictionally stressed component or vibration superimposed impact load, comprising a hard chrome layer, characterized in that on the hard chrome layer, a layer of a polysiloxane is applied. Wear protection layer according to claim 1, characterized in that the hard chrome layer has a layer thickness in the range of 2 to 20 microns and the layer of polysiloxane has a layer thickness in the range of 0.1 to 2 microns. Wear protection layer according to claim 1 or 2, characterized in that the polysiloxane of perfluorinated and / or partially fluorinated siloxanes. Wear protection layer according to claim 3, characterized in that the perfluorinated or partially fluorinated siloxanes are selected from

wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ^{6 are} each independently of one another -CF ₃ , -OCF ₃ , -O-SiR ¹ R ² R ⁵ , O-Si (CF ₃ ) ₃ , a linear or branched C ₁ to C ₁₅ alkyl, a vinyl, epoxy, methacryloxy, amino or aryl compound, or -OM-OR, wherein M is a metal atom, preferably selected from Ti, Al and Zr, and R is a C ₁ - to C ₃ alkyl or hydrogen, and R ⁷ , R ⁸ , R ⁹ , R ^{10 are} each independently hydrogen or fluorine, wherein in the radicals R ¹ to R ⁶ contained hydrogen may be partially or completely substituted by fluorine , Method for producing a wear protection layer according to one of claims 1 to 4, the following steps full: - Coating a component with a Hard chrome layer, - Applying a polysiloxane layer on the hard chrome layer. A method according to claim 5, characterized characterized in that the coating of the component with the hard chrome layer done by a galvanic coating process. Process according to claim 6, characterized characterized in that for the galvanic coating process a sulfuric acid chromium electrolyte is used which continues contains a catalyst solution. Method according to one of the claims 5 to 7, characterized in that for applying the polysiloxane layer on the hard chrome layer, first in a solvent dissolved siloxane by a dipping process or spraying process is applied. A method according to claim 8, characterized characterized in that the solvent is selected is from isopropanol, butanol, ethanol, ethylhexanol, methoxypropanol, Acetone, ethyl acetate, xylene or water. A method according to claim 8 or 9, characterized in that the siloxane is a fluorinated or partially fluorinated siloxane selected from

wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ^{6 are} each independently of one another -CF ₃ , -OCF ₃ , -O-SiR ¹ R ² R ⁵ , O-Si (CF ₃ ) ₃ , a linear or branched C ₁ to C ₁₅ alkyl, a vinyl, epoxy, methacryloxy, amino or aryl compound, or -OM-OR, wherein M is a metal atom, preferably selected from Ti, Al and Zr, and R is a C ₁ - to C ₃ alkyl or Are hydrogen, and R ⁷ , R ⁸ , R ⁹ , R ¹⁰ each independently represent hydrogen or fluorine, wherein hydrogen contained in the radicals R ¹ to R ⁶ may be partially or completely substituted by fluorine. Method according to one of the claims 8 to 10, characterized in that the component after application the polysiloxane layer by the dipping process or spraying process is heat treated. Process according to claim 11, characterized characterized in that the heat treatment at a temperature in the range of 120 to 350 ° C is performed by. Use of the wear protection layer according to any one of claims 1 to 4 as Coating for valve components in injection valves for internal combustion engines.