EP0911423B1 - Method for joining workpieces - Google Patents

Description

The invention relates to a method for connecting workpieces, whereby thermal spraying one spray layer or several spray layers which are at least partially a surface of a first workpiece and at least partially cover a surface of a second workpiece, and wherein a powdery filler material by means of a gas on the to be coated Surfaces. In industrial manufacturing there are connections of workpieces or parts of various types and geometries. The Requirements for the properties of the connections are different. The preparation of compounds from Workpieces that differ greatly in geometry and / or material.

DE-A-15 00 733 describes a method for the insoluble connection of non-to one another weldable material parts by coating with a wire or Powder spraying process with and without a protective gas atmosphere or by means of a Plasma spraying process with a protective gas atmosphere is known

Thermal spraying for coating is known as autogenous as process variants Flame spraying or high speed flame spraying, arc spraying, plasma spraying, detonation spraying and laser spraying.

The process variants of arc spraying are particularly suitable for the invention, of detonation spraying and laser spraying and in particular that of autogenous flame spraying or high speed flame spraying. According to the invention a flame spray process is therefore preferred as a thermal one Spraying process used.

• Übersicht und Einführung in das "Thermische Spritzen", Peter Heinrich, Linde-Berichte aus Technik und Wissenschaft, 52/1982, Seiten 29 bis 37, oder
• Thermisches Spritzen - Fakten und Stand der Technik, Peter Heinrich, Jahrbuch Oberflächentechnik 1992, Band 48, 1991, Seiten 304 bis 327, Metalf-Verlag GmbH,

beschrieben.Thermal spray processes are in general form, for example in

• Overview and introduction to " thermal spraying ", Peter Heinrich, Linde reports from technology and science, 52/1982, pages 29 to 37, or
• Thermal spraying - facts and state of the art, Peter Heinrich, yearbook surface technology 1992, volume 48, 1991, pages 304 to 327, Metalf-Verlag GmbH,

described.

Thermal spray processes are essentially characterized in that they enable evenly applied coatings. By thermal spraying Coatings can be applied by varying the spray materials can be adapted to different requirements. The spray materials can can be processed in the form of wires, rods or powder. With thermal In addition, thermal post-treatment can be provided for spraying.

In addition, a further thermal spray process has recently been developed, which is also known as cold gas spraying. It is about a kind of further development of high-speed flame spraying with powder. This method is described, for example, in European patent EP 0 484 533 B1 described. A filler material in powder form is used for cold gas spraying Commitment. However, the powder particles are not melted in a gas jet during cold gas spraying. Rather, the temperature of the gas jet is below the melting point the powder particles of the filler material (EP 0 484 533 B1) or only in slightly above the melting temperature of the powder. In the cold gas spray process becomes a "cold" or a compared to the conventional spraying process comparatively colder gas used. Nevertheless, the gas is just as in heated up to conventional methods, but only to temperatures below the melting point of the powder particles of the filler material or at temperatures of the gas jet from 100 K to 200 K above the melting point of the powder particles of the filler material.

The present invention is based on the object of a method for connecting of workpieces, which simplifies the connection of workpieces, cheaper or made possible at all. In particular, a connection of itself very different in geometry and / or material (in terms of Material composition as well as regarding the material properties) Workpieces are made possible.

The object is achieved in that the gas for thermal spraying Nitrogen, helium, argon, neon, krypton, xenon, a gas containing hydrogen, a carbon-containing gas, in particular carbon dioxide, oxygen, an oxygen containing gas, air, water vapor or mixtures of the aforementioned gases contains and that the powdered filler material on the to be coated Surfaces passed without the powder particles of the filler in the Gas jet are melted.

An essential feature of the invention is that the filler material in Powder form and not as wire.

• Metalle oder Metallegierungen mit sehr unterschiedlichem Schmelzpunkt,
• Metalle oder Metallegierungen mit unterschiedlicher Wärmeleitfähigkeit oder unterschiedlichem Wärmeausdehnungsverhalten,
• Metalle oder Metallegierungen, die beim gemeinsamen Aufschmelzen und der damit verbundenen Durchmischung anschließend beim Abkühlen spröde intermetallische Phasen bilden, welche die Festigkeit der Verbindung beeinflussen,
• Metall-Keramikverbindungen.

Workpieces made of different materials can be connected using the method according to the invention. The different materials can be:

• Metals or metal alloys with very different melting points,
• Metals or metal alloys with different thermal conductivity or different thermal expansion behavior,
• Metals or metal alloys which, when they are melted together and the associated mixing subsequently forms brittle intermetallic phases on cooling, which influence the strength of the connection,
• Metal-ceramic compounds.

Furthermore, the workpieces to be connected can vary greatly in terms of their geometry differ. For example, the method according to the invention can be used for fastening of webs or stiffeners in thin-walled constructions in particular can be used with advantage.

For the majority of applications, it will usually suffice that only a spray layer is produced. But it can also be two or more Spray coats can be applied. For example, this is for the first sprayed Layers useful that have a particularly high adhesive strength and / or a particular have good adhesion to both workpieces or where the material has one thermal expansion coefficient approximated to the material of the workpiece has. Such first spray layers are important, for example, if one of the workpieces to be connected is made of glass or ceramic and the Connection should be exposed to temperature changes. Comments on Production of a spray layer according to the invention also applies accordingly to Cases with multiple spray layers.

In any case, a workpiece assembly is created in the manner described a first workpiece and a second workpiece with a connection between two workpieces from one produced by thermal spraying Spray layer or several produced by thermal spraying Spray layers which at least partially have a surface of the first workpiece and at least partially covers a surface of the second workpiece or cover.

The statement that the powder particles of the filler material are not in the gas jet are to be melted in the context of the present invention also means that the particles in the gas jet are essentially not melted. This can be ensured that the temperature of the gas jet below the melting point of the powder particles of the filler material. But even with Gas jet temperatures from 100 K to 200 K above the melting point the powder particles of the filler material can be due to the extremely short residence time the particles in the gas jet melt or melt in the range of milliseconds Melting of the powder particles can be prevented. The importance of the higher Gas temperatures or the advantage of heating the gas is that in hotter gases the speed of sound is higher and therefore the Particle speed becomes comparatively greater.

The cold gas process has compared to conventional thermal processes Spraying a number of advantages. The thermal action and force action the surface of the substrate material is reduced, which results in unwanted Changes in the material properties of the substrate material prevented or can be reduced at least noticeably. Likewise, largely Changes in the Structure of the substrate material can be prevented. The one with the cold gas spraying process created layers have no or at least no pronounced texture, i.e. there is no preferred orientation of the individual grains or crystals. The substrate is also not heated by a flame or a plasma, so that none or only extremely small changes to the base body and no distortion of workpieces due to thermal stress due to thermal spraying.

It has been shown that the numerous procedural possibilities of Thermal spraying using the cold gas process for joining workpieces can be used. Due to the possibilities of using different Powder materials and powder mixtures open up a wide range for workpiece connections.

According to the invention, the gas for thermal spraying can be nitrogen, helium, Argon, neon, krypton, xenon, a hydrogen-containing gas, a carbon-containing one Gas, especially carbon dioxide, oxygen, an oxygen-containing Contain gas, air, water vapor or mixtures of the aforementioned gases. Next The gases air and / or helium known from EP 0 484 533 B1 are suitable nitrogen, argon, also for the gas carrying the powdered filler material, Neon, krypton, xenon, oxygen, a hydrogen-containing gas, a carbon-containing one Gas, especially carbon dioxide, water vapor or mixtures of the aforementioned gases and mixtures of these gases with helium. The proportion of helium of the total gas can be up to 90% by volume. A helium content of is preferred 10 to 50 vol .-% observed in the gas mixture.

It has been shown that by using different gases to accelerate and carrying the powdered filler the flexibility and Effectiveness of the process can be increased significantly. The so produced Layers adhere very well to a wide variety of substrate materials, for example on metal, metal alloys, ceramics, glass, plastics and composite materials. The coatings produced using the method according to the invention are of high quality, have an extremely low porosity and possess extremely smooth spray surfaces, so that there is usually a rework of the connection unnecessary.

The gases used according to the invention have a sufficient density and Speed of sound to the required high speeds of the powder particles to be able to guarantee. The gas can be inert and / or reactive gases contain. With the gases mentioned is the production of very dense and special uniform coatings possible, which is also due to their hardness and distinguish strength. The layers have extremely low oxide contents. They have no or at least no pronounced texture, i.e. There is none Preferred orientation of the individual grains or crystals. The substrate also becomes when cold gas spraying not heated by a flame or a plasma, so that none or only extremely minor changes to the base body and also no distortion of Workpieces occur due to thermal stresses due to thermal spraying.

In an embodiment of the invention, the workpieces to be connected touch each other the connection point when applying the spray layer or layers. in the The workpiece assembly produced in this way is below the connected workpieces the spray layer or the spray layers in direct contact.

According to another embodiment of the invention, the workpieces to be connected are at the junction when applying the spray layer or layers spaced from each other and by thermal spraying the space at the junction is filled. In the workpiece network is therefore between the connected workpieces with the sprayed Filler material or filler material filled space. Can with advantage in addition to the space at the junction, the adjacent surface area of the workpieces are coated.

The gas jet can be heated to a temperature in the range between 30 and 800 ° C are, all known powdery spray materials are used can. The invention is particularly suitable for wettable powders made of metals, metal alloys, Hard materials, ceramics and / or plastics.

In an embodiment of the method according to the invention, the temperature of the gas jet selected between 300 and 500 ° C. These gas temperatures are particularly suitable for the use of reactive gases or reactive Gas constituents. As reactive gas or gas components are in particular Hydrogen admixtures, carbon-containing gases or nitrogenous gases mention.

In a further development of the invention, a gas jet with a pressure of 5 to 50 bar used. Above all, working with higher gas pressures brings additional Advantages because the energy transfer in the form of kinetic energy is increased. It gas pressures in the range from 21 to 50 bar are particularly suitable. excellent Spray results were achieved, for example, with gas pressures of around 35 bar. The High pressure gas supply can, for example, by the in the German patent application DE 197 16 414.5 described method or the one described there Gas supply system can be ensured.

In the process according to the invention, the powder particles can run at a speed accelerated from 300 to 1600 m / s. Suitable in the process according to the invention speeds of the powder particles between 1000 and 1600 m / s, particularly preferably between 1250 and 1600 m / s, since in this case the Energy transfer in the form of kinetic energy is particularly high.

The powders used in the process according to the invention preferably have Particle sizes from 1 to 100 µm.

All suitable devices can be used to carry out the method according to the invention are used, in particular this applies to those in EP 0 484 533 B1 described device.

The invention and further details of the invention are described below of exemplary embodiments illustrated in the drawings.

Figur 1

eine erfindungsgemäß hergestellte Verbindung zweier Rohre;

Figur 2

zwei Ausschnittsvergrößerungen möglicher Rohrverbindungen zum Beispiel aus Figur 1;

Figur 3

ein erfindungsgemäß hergestellter Werkstückverbund bestehend aus einem Konstruktionsteil und einem Steg.

Here show:

Figure 1

an inventive connection of two pipes;

Figure 2

two enlargements of possible pipe connections, for example from Figure 1;

Figure 3

a workpiece composite manufactured according to the invention consisting of a structural part and a web.

In Figure 1, a workpiece composite of two tubes 1 and 2, for example from different materials. The applied spray layer 3 covers the surface of the first tube 1 and the surface in the connection area of the second pipe 2. The spray layer 3 and thus the pipe connection extends over the entire circumference of the pipe. The arrow shows that the Making the pipe connection the pipes can be turned.

Figure 2 shows two enlargements of possible sections in picture A and picture B. Pipe connections for example from Figure 1 in section. In picture A they touch Pipe pieces 1 and 2 are not immediately, but they are at a short distance arranged to each other. With the help of the auxiliary workpiece 4, which the Covering the area of the pipe interior, a connection is made through the spray layer 3 manufactured, which fills the pipe gap and the adjacent pipe ends of the Pipes 1 and 2 covered. The pipe ends of the pipes shown in Figure B of Figure 2 1 and 2 taper. The tube ends are for thermal spraying Establishing a pipe connection in contact with each other. The spray layer 3 fills also the space created by the tapering of the pipe ends.

Figure 3 shows a thin-walled structural part 5, which stiffened with a web 6 becomes. Construction part 5 and web 6 touch. I'm at the contact surfaces adjacent surface area are spray layers 3 for connecting the two Workpieces sprayed on.

Claims (7)

1. Method for joining workpieces (1, 2; 5, 6), in which, by thermal spraying, a sprayed layer (3) or a plurality of sprayed layers are produced, which at least partially cover a surface of a first workpiece (1; 5) and at least partially cover a surface of a second workpiece (2; 6), a pulverulent additive being passed onto the surfaces to be coated by means of a gas, characterized in that the gas for the thermal spraying contains nitrogen, helium, argon, neon, krypton, xenon, a hydrogen-containing gas, a carbon-containing gas, in particular carbon dioxide, oxygen, an oxygen-containing gas, air, water vapour or mixtures of the abovementioned gases, and in that the pulverulent additive is passed onto the surfaces to be coated without the powder particles of the additive being melted in the gas jet.
2. Method according to Claim 1, characterized in that the workpieces (1, 2; 5, 6) which are to be joined are in contact at the joining location when the sprayed layer (3) is being applied.
3. Method according to Claim 1, characterized in that the workpieces (1, 2; 5, 6) which are to be joined are arranged at a distance from one another at the joining location when the sprayed layer (3) is being applied, and the space which is present at the joining location is filled by the thermal spraying.
4. Method according to Claim 3, characterized in that in addition to the space at the joining location, the adjacent surface region of the workpieces (1, 2; 5, 6) is also coated.
5. Method according to one of Claims 1 to 4, characterized in that the temperature of the gas jet during the thermal spraying is in the range between 30 and 800ºC.
6. Method according to one of Claims 1 to 5, characterized in that the gas jet is at a pressure of from 5 to 50 bar during the thermal spraying.
7. Method according to one of Claims 1 to 6, characterized in that the powder particles are accelerated to a velocity of from 300 to 1600 m/s during the thermal spraying.

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