DE102006044612A1 - Method for cold gas spraying - Google Patents

Abstract

To methods for cold gas spraying, in which particles (20) are accelerated in a particular jet-shaped gas and impinge at high speed on a substrate (30), wherein the gas is compressed and heated and then accelerated by relaxing in a nozzle (10) and thereby cooling, so on, that reduces the adhesion of the particles (20) to the substrate (30) required critical speed and on a better connection of the particles (20) to the substrate (30) can be achieved, it is proposed that the substrate (30) is heated (40).

Description

Technical area

The The present invention relates to a method for cold gas spraying, in which particles in a particular jet-shaped gas be accelerated and at high speed on a substrate impinge, whereby the gas is compressed as well as heated and then by Relax in a nozzle is accelerated and cools down.

State of the art

Of the Advantage of the cold gas spraying over long used thermal Spraying processes, such as flame spraying, high-speed flame spraying, Arc spraying and plasma spraying, is that the spray material in Spray process is not melted. The adhesion of the particles Rather, it relies on its high kinetic energy on impact as well as on the then by deformation at the interfaces between particles and substrate and heat generated between the particles.

• – vom Spritzwerkstoff selbst,
• – von der Größe der Partikel und
• – von der Temperatur der Partikel im Moment ihres Aufpralls auf das Substrat abhängt. Kritische Geschwindigkeiten für verschiedene Spritzwerkstoffe und deren Abhängigkeit von der Partikelgröße und von der Partikeltemperatur werden beispielsweise von Tobias Schmidt, Frank Gärtner, Hamid Assadi und Heinrich Kreye im Aufsatz "Development of a generalized parameter window for cold spray deposition", Acta Materialia 54 (2006), Seiten 729 bis 742 , beschrieben.

It is known that the particles adhere to the substrate only when a critical speed is exceeded, and that this speed

• - from the spray material itself,
• - on the size of the particles and
• - depends on the temperature of the particles at the moment of their impact on the substrate. Critical speeds for different spray materials and their dependence on the particle size and the particle temperature are, for example, of Tobias Schmidt, Frank Gardener, Hamid Assadi and Heinrich Kreye in the article "Development of a generalized parameter window for cold spray deposition", Acta Materialia 54 (2006), pages 729-742 , described.

The Acceleration of the particles takes place during cold gas spraying in a supersonic gas jet. The height flow rate receives this supersonic gas jet at Passage through a so-called Laval nozzle. The powder is in front of the Nozzle in the Injected gas jet. The flow velocity of the gas and thus the acceleration of the particles is from the type of gas and its pressure and temperature at entry in the Laval nozzle dependent.

In rare special cases it is also possible the particles with a gas jet, the only very high speeds, but not supersonic speed achieved to accelerate to the required critical speed.

With Helium as a process gas are at the same gas pressure and at the same Gas temperature much higher Gas and particle velocities as with nitrogen or with compressed air reached. The reason for that is the much higher Sound velocity for Helium. In principle, however, any gas can be used.

at all process gases increase the speed of the particles with the Pressure and with the temperature of the gas on. Especially high particle speeds are therefore achieved when the largest possible with the plant technology Pressure and with the largest possible Gas temperature is injected.

Conventional cold gas spraying equipment, such as the KINETIKS ^® 4000 of the company CGT Cold Gas Technology GmbH, Ampfing, can be operated at pressures of up to about 3.5 megapascals, and at temperatures of up to about 900 degrees Celsius. However, even with lower gas temperatures in the range from about 300 degrees Celsius to about 600 degrees Celsius, so-called caking of the powder in the nozzle occurs at many metals, so that then can only be injected with correspondingly lower gas temperature.

• – durch die Art des Gases bzw. durch den Wärmeübergang zwischen Gas und Partikel sowie
• – durch die anlagentechnisch mögliche maximale Gastemperatur bzw. durch die zur Vermeidung von Pulveranbackungen in der Düse gerade noch tolerierbare Gastemperatur

begrenzt.The heating of the process gas serves on the one hand to increase the flow velocity of the gas and thus the speed of the particles. By heating the gas, on the other hand, the temperature of the particles increases at the moment of impact, which favors their subsequent deformation. The minimum speed required for adhesion is thereby significantly reduced. The maximum achievable particle temperature is

• - By the nature of the gas or by the heat transfer between gas and particles as well
• - By the maximum possible gas turbine temperature or by the just tolerable to avoid Pulveranbackungen in the nozzle gas temperature

limited.

The Temperature of the particles at the moment of impact is significantly lower as the gas temperature. This is because of the particles only for the duration of milliseconds are located in the hot gas jet and that the gas jet in its relaxation in the divergent area the nozzle cools very much, to Part far below room temperature.

Even if the residence time of the powder in the hot gas before entering the nozzle throat according to the publication WO 2006/034778 A1 increased by a about 100 millimeters to about 200 millimeters long pre-chamber or by a correspondingly extended convergent nozzle section and Pressure and temperature of the gas increases to the system technically possible maximum values today, the maximum impact temperature is limited upwards.

• – durch die Integration eines zweiten Heizers in die Pistole (vgl. Druckschrift WO 2006/034777 A1 ),
• – durch die Verlängerung des konvergierenden Düsenabschnitts bzw. den Einbau einer verlängerten Vorkammer in die Spritzpistole (vgl. Druckschrift WO 2006/034778 A1 ) und/oder
• – durch die Möglichkeit des Nachheizens der Partikel auf deren Weg zwischen der Pistole und dem Substrat durch Mikrowellenheizung (vgl. Druckschrift EP 1 593 437 A1 ),

bedeutende Fortschritte gemacht hat, besteht im Hinblick auf eine erstrebenswerte Verringerung der zum Haften der Partikel am Substrat erforderlichen kritischen Geschwindigkeit sowie auf eine bessere Anbindung der Partikel an das Substrat noch ein weiteres Entwicklungspotenzial.Although now the cold gas spraying lately by the development of such nozzles to increase the particle velocity and measures to increase the particle temperature, such as

• - By the integration of a second heater in the gun (see WO 2006/034777 A1 )
• - By the extension of the converging nozzle section or the installation of an extended pre-chamber in the spray gun (see WO 2006/034778 A1 ) and or
• - By the possibility of Nachheizens the particles on their way between the gun and the substrate by microwave heating (see EP 1 593 437 A1 )

Significant progress has been made in terms of a desirable reduction in the critical velocity required to adhere the particles to the substrate, as well as better attachment of the particles to the substrate.

presentation OBJECT OF THE INVENTION: OBJECT, SOLUTION, ADVANTAGES Starting from the shortcomings and inadequacies set out above and of the prior art is the present invention the task is based on a method of the type mentioned above to further develop that required for adhering the particles to the substrate Reduces critical speed as well as better connectivity the particle can be achieved on the substrate.

These The object is achieved by a method with the specified in claim 1 Characteristics solved. advantageous Embodiments and expedient developments The present invention is characterized in the subclaims.

therefore For example, the present invention is based on heating or heating the substrate or the workpiece.

To the Example in dependence from the possibilities of the chosen Warmth- or heating medium here is the option, the entire substrate or the whole workpiece to warm up or to heat up, which is especially true for small sized substrates or for small workpieces can be useful.

• – am Auftreffort der Partikel und/oder
• – im Bereich des Auftrefforts der Partikel und/oder
• – im Umkreis des Auftrefforts der Partikel

erwärmt oder aufgeheizt werden, so zum Beispiel am oder im Bereich des Orts, an dem die in einem Gasstrahl beschleunigten, auf das Substrat bzw. Werkstück gerichteten Partikel in festem Zustand auf das Substrat bzw. Werkstück aufprallen oder auftreffen.However, the substrate or workpiece may only

• - At the impact of the particles and / or
• - In the area of the impact of the particles and / or
• - in the vicinity of the place of impact of the particles

be heated or heated, for example, at or in the region of the location at which the accelerated in a gas jet, directed onto the substrate or workpiece particles in the solid state impact or impinge on the substrate or workpiece.

• – eine geringere, insbesondere laterale, Ausdehnung oder
• – eine größere, insbesondere laterale, Ausdehnung

als der Partikelstrahl aufweisen. Hierbei kann der Art des eingesetzten Wärmemediums oder Heizmittels bei der Dimensionierung des aufgeheizten Bereichs oder Umkreises entscheidende Bedeutung zukommen.In an advantageous embodiment of the present invention, the heated area or perimeter

• A smaller, in particular lateral, expansion or
• - A larger, especially lateral, expansion

have as the particle beam. Here, the type of heat medium or heating medium used in the dimensioning of the heated area or perimeter crucial importance.

The The underlying principle of the present invention is therefore in it, the substrate, in particular at the location of the particle impact, to warm up or heat and thereby soften or ductilize, to promote the deformation of the substrate during particle impact.

According to one particularly advantageous embodiment of the present invention The temperature of the substrate may be at a temperature between Impact temperature of the particles and the melting temperature of the particles elevated become.

in this connection in the exemplary case of copper particles with a size of about fifty microns an increase the substrate temperature to only about 200 degrees Celsius above the Impact temperature of the particles already a reduction of sticking required minimum speed of the particles by about 100 meters per second.

By the invention better Deformability of the substrate may be the first to adhere the particles necessary critical speed can be reduced so that with otherwise the same impact conditions by a larger area and Homogeneous heating of the interface between particle and substrate a much better connection of each particle to the substrate is reached.

This has, on the one hand, the fact that the critical velocity required to adhere the particles to the substrate is already lower in comparison with the prior art, lower gas pressure and clotting gerer gas temperature is reached; On the other hand, the critical speed is still achieved with compared to the prior art larger and therefore slower particles, so that is extended by the present invention, the range of applications and application of the method of cold gas spraying under various conditions.

in this connection the person skilled in the art of cold gas spraying especially appreciated know that powder with coarser and thus applicable in contrast to the prior art Particles usually produce more cheaply are as powders with finer particles, as in the prior art are compulsory.

at otherwise equal impact conditions causes the possibility lowering of the critical speed due to softening and ductilization of the substrate a significantly higher application rate or a significantly higher Order efficiency (so-called deposition efficiency), this being according to the invention increased application efficiency in a larger mass of the adhering powder with respect to the mass of the impacting powder reflects.

• – sowohl die innere Festigkeit (sogenannte Cohesive Strength)
• – als auch die plastische Verformbarkeit (sogenannte Duktilität)

beträchtlich verbessert werden. Darüber hinaus wird insbesondere auf verhältnismäßig harten Substraten die Haftfestigkeit der Schicht (sogenannte Bond Strength) deutlich gesteigert.Furthermore, the present invention also achieves a significant improvement in the mechanical properties of the layers. Here you can

• - both the internal strength (so-called Cohesive Strength)
• - as well as the plastic deformability (so-called ductility)

considerably improved. In addition, the adhesion of the layer (so-called bond strength) is significantly increased, especially on relatively hard substrates.

• – durch Integrieren mindestens eines zweiten Wärme- oder Heizmittels in der Düse und/oder
• – durch Verlängern des konvergenten Abschnitts der Düse und/oder
• – durch Einbauen mindestens einer verlängerten Vorkammer in die Spritzpistole, der die Düse zugeordnet ist, und/oder
• – durch Mikrowellenheizung im Bereich zwischen der Düse und dem Substrat, Energie zugeführt werden.

According to an expedient embodiment of the present invention, not only the substrate but also the particles, in particular

• By integrating at least one second heating or heating means in the nozzle and / or
• By extending the convergent section of the nozzle and / or
• By incorporating at least one elongated prechamber into the spray gun associated with the nozzle, and / or
• - Are supplied by microwave heating in the region between the nozzle and the substrate, energy.

On this way can - besides the warming or heating the substrate - too an autonomous warming or heating of the particles be accomplished, so that in synergetic Both the particles and the substrate improve with regard to layer or mold production. The necessary for the production of layers or mold plastic energy thus results on the one hand from the kinetic energy and the Heat the Particles and on the other hand from the heat of the substrate. This leads to special good results in the layer or mold production, in particular in the coating of substrate materials and / or in the production of moldings using a powdered spray material.

Independent of this or in conjunction with this, in the case of a moving particle beam heating or heating the substrate in an appropriate manner to the place of impact be limited or ahead of the place of impact. This can be particularly favorable Way then be accomplished when the heated or heated area of the substrate a smaller, in particular lateral, expansion as the particle beam.

The The present invention further relates to a heat or Heating means for heating or heating a substrate in a method according to the above set forth.

• – um mindestens eine mindestens einen Kontakt zum Substrat aufweisende Wärme- oder Heizplatte und/oder
• – um mindestens einen Wärme- oder Heizstrahler, insbesondere mindestens eine Heizlampe oder Infrarotlampe, und/oder
• – um mindestens ein induktives Wärme- oder Heizmittel, insbesondere basierend auf dem Einkoppeln mittel- oder hochfrequenter elektromagnetischer Strahlung, und/oder
• – um mindestens einen Laserstrahl und/oder
• – um mindestens einen Lichtbogen und/oder
• – um mindestens einen Plasmastrahl

handeln. in zweckmäßiger Weise können mindestens zwei der vorgenannten Wärme- oder Heizmittel auch in Kombination miteinander zum Einsatz gelangen.In this heating or heating means, it may preferably

• - At least one at least one contact with the substrate having heat or hot plate and / or
• - At least one heat or radiant heater, in particular at least one heat lamp or infrared lamp, and / or
• - At least one inductive heating or heating means, in particular based on the coupling medium or high frequency electromagnetic radiation, and / or
• - At least one laser beam and / or
• - at least one arc and / or
• - at least one plasma jet

act. Conveniently, at least two of the aforementioned heating or heating means can also be used in combination with each other.

The The present invention further relates to a cold gas spray system, having at least one heat or heating means according to the above set forth.

Finally, the present invention relates to the use of a method according to the kind set out above and / or at least one heating or heating means according to the kind set out above and / or at least one cold gas spraying unit according to the above-described type of layer or mold production, in particular in the coating of Substrate materials and / or in the production of moldings using a powdered spray material.

Brief description of the drawings

As already discussed above, there are various possibilities for embodying and developing the teaching of the present invention in an advantageous manner. For this purpose, reference is made on the one hand to the claims subordinate to claim 1, on the other hand, further embodiments, features and advantages of the present invention will be described below with reference to 1 illustrated embodiment explained in more detail.

It shows:

1 a schematic representation of an exemplary embodiment of a cold gas spray system according to the present invention, in which the substrate is heated or heated according to the method according to the present invention at the impact of the particles or in the region of incidence of the particles or in the vicinity of the impact of the particles.

Best way to execute the invention

The basis 1 illustrated embodiment of a cold gas spray system 100 according to the present invention shows a nozzle 10 with a convergent nozzle section 12 , the nozzle neck 14 in the nozzle outlet 16 passes. The nozzle 10 is one (for reasons of clarity of presentation in 1 not explicitly reproduced) spray gun assigned.

Inside the nozzle 10 become the particles 20 accelerated to supersonic speed for layer or mold production in a gas jet, hit the substrate at high speed 30 on and form there the coating; to accelerate the particles 20 the gas is compressed and advantageously heated and then by relaxation in the nozzle 10 accelerates and cools down.

Regarding the basis 1 illustrated embodiment of the present invention is now basically to be considered that the cold gas spraying for adhering the particles 20 required heat by plastic deformation at the interface between the particles 20 and the substrate 30 arises.

In order now to consider the bonding conditions for the spraying of metals or composite materials with metallic components on metallic and non-metallic substrates 30 to improve, it is therefore sufficient according to the invention, instead of the particles 20 the substrate 30 at the place of impact 32 the particle 20 and / or in the area of the place of impact 32 the particle 20 and / or around the place of impact 32 the particle 20 to heat or to heat.

• – durch Integrieren einer zweiten Heizeinrichtung in der Spritzpistole,
• – durch Verlängern des konvergierenden Düsenabschnitts bzw. Einbauen einer verlängerten Vorkammer in die Spritzpistole und/oder
• – durch Mikrowellennachheizung der Partikel auf deren Weg zwischen der Düse 10 und dem Substrat 30,

als auch dem Substrat 30, zum Beispiel durch nachstehend näher erläuterte Wärme- oder Heizmittel 40, Energie zuzuführen, so dass sowohl die Partikel 20 als auch das Substrat 30 über die hierbei erfolgende Erwärmung oder Aufheizung plastisch verformbar sind.In the context of the present invention, however, it is also advantageous, both the particles 20 , for example

• By integrating a second heating device in the spray gun,
• By extending the convergent nozzle section or installing an extended prechamber into the spray gun and / or
• - By microwave Nachheizung the particles on their way between the nozzle 10 and the substrate 30 .

as well as the substrate 30 , for example by heating or heating means explained in more detail below 40 To supply energy so that both the particles 20 as well as the substrate 30 can be plastically deformed by the resulting heating or heating.

• – vom Werkstoff des Substrats 30 und/oder
• – von den Abmessungen des Substrats 30

erfolgen, zum Beispiel mit einer elektrischen Widerstandsheizung, mit einer Induktionsheizung oder mit einer Flamme.Heating or heating the substrate 30 That is, the choice of the heat medium or heating medium 40 can depend on

• - From the material of the substrate 30 and or
• - on the dimensions of the substrate 30

done, for example, with an electrical resistance heater, with an induction heater or with a flame.

It is also possible to heat or heat the substrate 30 with a quartz lamp of higher power density, whose light is on the impact site 32 the particle 20 is focused.

The heating or heating of the substrate is also particularly effective 30 with a laser beam that hits the point of impact 32 the particle 20 is focused or this place of incidence 32 the particle 20 is ahead.

In addition, the desired temperatures of the substrate 30 also be adjusted by a focused plasma jet or by an arc.

By means of the 1 illustrated embodiment of the present invention, the adhesion of the particles 20 on the substrate 30 Required critical speed decreases as well as a better binding of the particles 20 to the substrate 30 be achieved. This with increasing temperature of the particles 20 decreasing critical or minimum velocity of the particles 20 is given by the fact that the particles 20 below the threshold of this critical or minimal velocity, it is no longer strong enough on the substrate 30 stick because of the particle 20 inherent kinetic energy, in which the particle velocity is known to be square, is too low. If at least the critical or minimum speed is maintained, so is with the basis 1 illustrated embodiment of the cold gas spray system 100 a better and more consistent adhesion of the particles 20 on the substrate or workpiece 30 guaranteed.

Such as a critical or minimal velocity of the particles 20 There is also one with increasing temperature of the particles 20 also decreasing maximum velocity of the particles 20 ; Above the threshold of this maximum speed, the particles spray 20 because of their too high kinetic energy, in which the particle velocity is known to be square, from the substrate 30 back, that is the order rate or the order efficiency (so-called deposition efficiency) is too low.

The region of optimum layer or mold production is located between the (lowerable according to the invention) critical or minimum velocity of the particles 20 and the maximum velocity of the particles 20 ,

100

Cold spray system

10

jet

12

Convergent section of the nozzle 10

14

Neck of the nozzle 10

16

Outlet of the nozzle 10

20

particle or particle beam

30

substratum or workpiece

32

Impact of the particle 20 on the substrate 30

40

Heat or heating

Claims (12)

Method for cold gas spraying, in which particles ( 20 ) are accelerated in a particularly jet-shaped gas and at high speed onto a substrate ( 30 ), wherein the gas is compressed and heated and then by relaxing in a nozzle ( 10 ) and thereby cooling, characterized in that the substrate ( 30 ) heated up ( 40 ) becomes. Method according to claim 1, characterized in that the substrate ( 30 ) at the place of impact ( 32 ) of the particles ( 20 ) and / or in the area of the place of impact ( 32 ) of the particles ( 20 ) and / or in the vicinity of the place of impact ( 32 ) of the particles ( 20 ) heated up ( 40 ) becomes. Process according to claim 1 or 2, characterized in that the heated ( 40 ) Area or perimeter - a smaller, in particular lateral, expansion or - a larger, in particular lateral, extent than the jet of particles ( 20 ) having. Method according to at least one of claims 1 to 3, characterized in that the heating ( 40 ) of the substrate ( 30 ) in the case of a moving jet of particles ( 20 ) on the place of impact ( 32 ) is limited or the place of impact ( 32 ) leads. Method according to at least one of claims 1 to 4, characterized in that the temperature of the substrate ( 30 ) to a temperature between the impact temperature of the particles ( 20 ) and the melting temperature of the particles ( 20 ) is increased. Method according to at least one of claims 1 to 5, characterized in that the particles ( 20 ) are heated. Method according to at least one of claims 1 to 6, characterized in that the substrate ( 30 ) By means of at least one at least one contact to the substrate ( 30 ) having heating or heating plate and / or - by means of at least one heat or radiant heater, in particular by means of at least one heat lamp or infrared lamp, heated ( 40 ) becomes. Method according to at least one of claims 1 to 7, characterized in that the substrate ( 30 ) inductively, in particular by coupling medium or high frequency electromagnetic radiation, heated ( 40 ) becomes. Method according to at least one of claims 1 to 8, characterized in that the substrate ( 30 ) is heated by means of at least one laser beam and / or by means of at least one electric arc and / or by means of at least one plasma jet ( 40 ) becomes. Heating or heating means ( 40 ) for heating a substrate ( 30 ) in a method according to any one of claims 1 to 9. Cold gas spray system ( 100 ), characterized by at least one heating or heating means ( 40 ) according to claim 10. Use of a method according to any one of claims 1 to 9 and / or at least one heating or heating means ( 40 ) according to claim 10 and / or at least one cold gas spray system ( 100 ) according to claim 11 for layer or mold production, in particular in Be layering of substrate materials and / or in the production of moldings using a powdered spray material.