EP1994203A1

EP1994203A1 - Coating a functional component which is subject to a thermal load and erosion

Info

Publication number: EP1994203A1
Application number: EP07722820A
Authority: EP
Inventors: Manfred Laudenklos
Original assignee: KS Aluminium Technologie GmbH
Current assignee: Gelita AG; KS Huayu Alutech GmbH
Priority date: 2006-03-07
Filing date: 2007-02-15
Publication date: 2008-11-26
Also published as: JP5219845B2; JP2009529097A; CN101501246A; BRPI0708628A2; KR20080111028A; US20090220773A1; DE102006010875A1; WO2007101529A1

Abstract

The invention relates to a functional component from metal which is subject to a thermal load or a thermal load and erosion and to at least one surface of which a coating is applied, said coating consisting of a binder phase containing zirconium fluoride and a material embedded in said binder phase. The invention also relates to a mold release agent for producing said coating and to a method for applying said coating to a functional component.

Description

KS Aluminum Technology AG, Neckarsulm

DESCRIPTION

Coating of a thermally and erosively loaded functional component

The invention relates to a metallic functional component, which is exposed to a thermal or a thermal and erosive load and on which a coating is applied to at least one surface, wherein the coating consists of a binder phase and a material embedded in the binder phase. Moreover, the invention relates to a release agent for producing a coating on a functional component and moreover relates to a method for producing a coating on a metallic surface of a functional component.

For example, components that are subjected to thermal or thermal and erosive stress while flowing, pressurized, or exposed to a medium perform, for example, the function of a power transmission or a baffle. In this function, they are charged with flowing or expanding media. In many cases, it comes to strong temperature fluctuations, so that the components must meet the condition of temperature resistance. In many cases, components which are in contact with flowing media also lead to deposits, so that these components are usually provided with coatings. Typical examples of such functional components are, for example, pistons, cylinder head calottes and the entire area of exhaust gas recirculation in the motor vehicle. In addition to the erosive loading of these components, these components are also inferior to high thermal loads and temperature fluctuations. To protect such functional components a variety of coatings and coating methods are known.

DE 101 24 434 A1 discloses a process for producing a coating and a coating for metals or metal alloys, such as steels, sintered metals or aluminum alloys from the fields of automobile construction and mechanical engineering. The aim of this coating is to protect the materials mentioned against wear and corrosion. The coating consists of an inorganic matrix phase, which consists at least largely of a phosphate and a material embedded therein. In one embodiment, the coating is an inorganic one Matrix phase of aluminum phosphate, are embedded in the materials such as alumina or graphite. Such coatings are preferably applied to the substrate to be coated via water-based gels or dispersions of dissolved monoaluminum phosphate and powdered functional materials dispersed therein, dried and baked at typical temperatures of 150 ^° C. to 500 ^° C. in an oven.

Another coating for aluminum materials is known from DE 699 08 837 T2. The coating here refers to the surface of a piston skirt having a hard anodized coating and a composite polymer coating applied to the hard anodized coating. The composite polymer coating comprises a variety of solid and lubricious particles in a heat-resistant polymer matrix that can withstand engine operating temperatures. As a lubricant in this case, the known lubricant materials graphite, boron nitride, molybdenum et cetera are used.

The object of the present invention is to develop a coating of thermally or thermally and erosively loaded functional surfaces on components, which forms a chemical bond with the base material of the functional component and thus counteracts the erosive and thermal stresses on the functional components. In addition, the coating should be easy to apply and have a high adhesion to the base material. Moreover, it is an object of the invention to provide a release agent for producing such a layer, which is inexpensive to manufacture and easy to apply. Another object of the invention is to provide a method capable of producing such a layer and which produces high adhesion between the binder and the base material.

The object according to the invention is achieved with respect to the functional component provided with a coating in that the binder phase is chemically bonded to the base material of the functional component and that the binder phase is formed from a polymer of polymerized zirconium fluoride, the functional component being part of an internal combustion engine. The use according to the invention of a binder phase of polymerized zirconium fluoride now makes it possible to produce a chemical bond with the base material, and thus to produce a firmly adhering layer on the functional component. Such coatings increase the life of the functional components and reduce, with improved effect the complicated and cost-intensive use of methods for improving the thermal shock behavior of the base materials. Furthermore, deposits are avoided by means of the layer according to the invention, which in turn serves to reduce emissions of motor vehicles. In advantageous embodiment variants of the invention, structural parts of the form AI ₂ O ₃ and / or SiO ₂ and / or TiO ₂ and / or ZrO _{2 are} incorporated into the binder phase. The polymer chains enclose the structural parts and bind the structural parts to the base material. Here, the fluoride is either a chemical bond with an existing iron in the base material or a non-metal such as aluminum. It is thus produced a firmly adhering layer on the functional component, which forms a great security against erosive loads by means of a chemical bond with the base material and the inclusion of the structural elements in the polymer chains. Here are the hard structural parts, which are present as oxides, as a wear carrier and the binder phase as a binder between the base material and structural element. The structural parts are present in a fraction of 80nm to 200nm and form with up to 10 wt .-%, the largest proportion of particulate materials in the coating. The structural parts have a relatively coarse surface structure, so that on the one hand the structural parts interlock with each other and at the same time ensure a good hold in the binder phase.

Primary parts of the form Al ₂ O ₃ and / or SiO ₂ and / or ZnO and / or TiO ₂ and / or ZrO ₂ and / or CeO are preferably introduced into the binder phase with the structural parts. In the gaps between the structural parts, the primary parts are integrated. In particular, by the size of the primary parts of 2nm to 80nm, the primary parts are optimally suited to serve as fillers between the structural parts. This results in a very smooth surface, which in turn counteracts erosion and deposition of the soot particles acting on the functional part, for example contained in an exhaust gas of an exhaust gas recirculation channel. The very smooth and resistant surface thus enables the advantage according to the invention that the functional components provided with a coating according to the invention have a long service life. The primary parts are preferably present in proportions of 1 wt .-% to 3 wt .-% in the coating.

In a further advantageous embodiment variant of the invention, sliding parts of the form boron nitride and / or magnesium aluminum silicate and / or molybdenum disulfide and / or silicate minerals, for example mica, are incorporated into the binder phase. The sliding parts are contained in the coating at levels of up to 5% by weight. The much larger sliding parts with dimensions of 2 μm to 15 μm are likewise held by the polymer chains or lie between the structural parts in the coating.

Thicknesses between 1 .mu.m and 80 .mu.m are preferably provided as layer thicknesses. A thickness of between 25 μm and 60 μm is preferred on the surface of the functional component. Functional components are for example components such as pistons, a cylinder head calotte, or parts of the exhaust gas recirculation in a motor vehicle. Here, the functional components are made of aluminum alloys or steel. It is also possible to form a coating according to the invention on a functional component made of cast iron, in particular a cast iron of the form GG ₁ GGG, GGV.

The object according to the invention is achieved in relation to the release agent for producing a coating on a functional component such that the release agent is formed from a demineralized water and contains the following constituents:

an acid generator, in particular in the form of sodium hydroxide and / or potassium hydroxide and / or aluminum chloride,

a binder of zirconium fluoride, especially in the form of ZrF ₆ , and

an organic dispersant, such as mica.

By means of the acid generator, it is possible to adjust the acid content and thus the pH of the release agent and thus to control the reaction rate and formation of the polymers. Preferably, a pH of 4 to 5 is set in the release agent. By using the release agent, it is now possible to produce a coating according to claim 1. In a preferred embodiment, structural parts and primary parts are contained in the release agent, which are applied by means of spraying or dipping of the functional component on the surface of the material of the functional component. It is also advantageous to incorporate sliding parts of the form boron nitride and / or magnesium aluminum silicate and / or molybdenum disulfide into the release agent. The fractions of the structural parts lie between 80nm to 200nm of the primary parts between 2nm and 80nm and the sliding parts between 2μm and 15μm. The advantage here is the gelatin, which forms nanoparticles on its own. In the limits specified in the dependent claims binder in a size proportion of up to 5 wt .-% are added to the release agent. The structural parts are up to 10 wt .-%, the Primary parts of up to 3 wt .-% and the sliding parts in a proportion of up to 5 wt .-% added to the release agent.

Through the targeted selection of the addition of the structural parts, primary parts, sliding parts and zirconium fluoride binder as a release agent can be prepared which has a high liquidity and is preferably sprayed by simple means on the surface of the functional component.

With regard to the method for producing the coating on a surface of the functional component, the coating according to the invention is produced by first applying a release agent to the surface and then heating the functional component to a temperature of at least 200 ^° C., so that a chemical bond is achieved of the fluoride with the base material and a polymerization of the binder takes place. Advantageously, the heating is generated by means of a high-frequency electric field that, for example, is applied capacitively or inductively to the functional component. As a result of this direct warming up, as occurs, for example, in the case of inductive heating, the surface can be heated very uniformly. Preferred frequency ranges for heating by means of a high-frequency electric field are in this case 100 kHz up to 10 MHz, wherein preferably about 4 MHz are used. With a heating at 4 MHz, this results in a penetration depth of the fluoride of 0.2 to 0.3 mm. It is thus produced a very good adhesion coating on the functional component.

The polymer chains serve on the one hand for the cohesion of the layer and on the other hand, they are advantageous because they grow under thermal stress and thus increase the elasticity of the layer. With cyclic thermal stress, therefore, no premature component failure occurs due to crack formation of the coating, since the coating according to the invention can elastically follow the expansions of the base material. The inventive construction of the layer, a temperature resistance can be achieved up to about 1300 ⁰ C. The fluoride binder systems used have a polymerization temperature of about 220 ⁰ C and a glazing temperature of 83O ⁰ C. The adhesion to the base material is hereby ensured even in almost glazed or vitrified state by the chemical bond to the base material. It is preferred, however, to ensure that the operating temperatures in the field of application of the functional components are below the glazing temperature, so that the coatings are elastic Range and thus in their coefficient of expansion similar to that of the base material.

Claims

KS Aluminum-Technologie AG, Neckarsulm 14.02.2007P ATENTANSPR Ü CHE

1. Metallic functional component which is exposed to a thermal or a thermal and erosive load and on which a coating of a binder phase and a binder material embedded in the binder phase material is applied to at least one surface, characterized in that the functional component is part of an internal combustion engine and that the binder phase is chemically bonded to the base material of the functional component and the binder phase is formed from a polymer of polymerized zirconium fluoride.

2. Functional component according to claim 1, characterized in that in the binder phase embedded material is a structural part of the form AI ₂ O ₃ and / or SiO ₂ and / or TiO ₂ and / or ZrO ₂ in a fraction of 80nm to 200nm, wherein the Structural parts are enclosed by the polymer.

3. Functional component according to claim 2, characterized in that the material embedded in the binder phase of primary parts of the form AI ₂ O ₃ , SiO ₂ , ZnO, ZrO _2, CeO, TiO _{2 is formed} in a fraction of 2nm to 80nm, wherein the Primary parts are embedded in the gaps between the structural parts and the primary parts are enclosed by the polymer.

4. Functional component according to claim 1 or 2 or 2 and 3, characterized in that the material embedded in the binder phase is a sliding part of the form boron nitride and / or magnesium aluminum silicate and / or molybdenum disulfide, in a fraction of 2μm to 15μm, wherein the sliding parts of enclosed by the polymer.

5. Functional component according to one or more of claims 1 to 4, characterized in that the functional component of an aluminum alloy or a steel or a cast iron, in particular a cast iron of the form GG ₁ GGG, GGV is formed.

6. Functional component according to claim 5, characterized in that the functional component is an iron-containing component and that the coating is connected by means of bound iron fluoride with the base material.

7. Functional component according to one or more of claims 1 to 4, characterized in that the layer is present in a thickness of 1 .mu.m to 80 .mu.m, preferably a thickness of 25 .mu.m to 60 .mu.m on the surface.

8. Functional component according to one or more of claims 1 to 5, characterized in that the functional component is a piston, a Zylinderkopfkalotte or a part of an exhaust gas recirculation.

9. release agent for producing a coating on a functional component, characterized in that the release agent is formed from a demineralized water and contains at least the following constituents:

an acid generator, in particular in the form of sodium hydroxide and / or potassium hydroxide and / or aluminum chloride and

a zirconium fluoride binder.

10. Release agent according to claim 9, characterized in that in the release agent, a proportion of structural parts of the form AI ₂ O ₃ and / or SiO ₂ , is contained in a fraction of 80nm to 200nm.

11. A release agent according to claim 10, characterized in that in the release agent, a proportion of primary parts of the form AI ₂ O ₃ and / or SiO ₂ and / or ZnO and / or TiO ₂ and / or ZrO ₂ and / or CeO, in a fraction from 2nm to 80nm is included.

12. Release agent according to one or more of claims 9 to 10, characterized in that in the release agent, a proportion of sliding parts of the form boron nitride and / or magnesium aluminum silicate and / or molybdenum disulfide, in a fraction of 2μm to 15μm is included.

13. Release agent according to one or more of claims 9 to 12, characterized in that in the release agent by means of the acid generator, a pH of 4 to 5 is set.

14. Release agent according to one or more of claims 9 to 13, characterized in that the proportion of the binder in the release agent is less than or equal to 5 wt .-%.

15. Release agent according to one or more of claims 9 to 14, characterized in that the proportion of structural parts in the release agent is less than or equal to 10 wt .-%.

16. release agent according to one or more of claims 9 to 15, characterized in that the proportion of primary parts in the release agent is less than or equal to 3 wt .-%, and preferably between 1 wt .-% and 3 wt .-% is.

17. Release agent according to one or more of claims 9 to 16, characterized in that the proportion of the sliding parts in the release agent is less than or equal to 5 wt .-%.

18. A method for producing a coating on a metallic surface of a functional component, according to one or more of claims 1 to 8, by means of a release agent according to one or more of claims 9 to 17, characterized in that

- The surface first applied to the release agent and that

- Then the functional component is heated to a temperature of at least 200 ⁰ C, so that a chemical bonding of the fluoride with the base material and a polymerization of a binder in the release agent.

19. The method according to claim 18, characterized in that the heating takes place by means of a high-frequency electric field in a frequency range of 100 kHz to 10 MHz, preferably in a frequency range of 4 MHz, inductively or capacitively.