EP1791645B1 - Method for cold gas spraying and cold gas spraying pistol with increased retention time for the powder in the gas stream - Google Patents

Method for cold gas spraying and cold gas spraying pistol with increased retention time for the powder in the gas stream Download PDF

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Publication number
EP1791645B1
EP1791645B1 EP05785200A EP05785200A EP1791645B1 EP 1791645 B1 EP1791645 B1 EP 1791645B1 EP 05785200 A EP05785200 A EP 05785200A EP 05785200 A EP05785200 A EP 05785200A EP 1791645 B1 EP1791645 B1 EP 1791645B1
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EP
European Patent Office
Prior art keywords
nozzle
particles
gas
cold
powder injection
Prior art date
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Not-in-force
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EP05785200A
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German (de)
French (fr)
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EP1791645A1 (en
Inventor
Peter Heinrich
Heinrich Kreye
Tobias Schmidt
Thorsten Stoltenhoff
Frank GÄRTNER
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Linde GmbH
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Linde GmbH
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1481—Spray pistols or apparatus for discharging particulate material
    • B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/16—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed
    • B05B7/1606—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed the spraying of the material involving the use of an atomising fluid, e.g. air
    • B05B7/1613—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed the spraying of the material involving the use of an atomising fluid, e.g. air comprising means for heating the atomising fluid before mixing with the material to be sprayed
    • B05B7/162—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed the spraying of the material involving the use of an atomising fluid, e.g. air comprising means for heating the atomising fluid before mixing with the material to be sprayed and heat being transferred from the atomising fluid to the material to be sprayed
    • B05B7/1626—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed the spraying of the material involving the use of an atomising fluid, e.g. air comprising means for heating the atomising fluid before mixing with the material to be sprayed and heat being transferred from the atomising fluid to the material to be sprayed at the moment of mixing
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/02—Coating starting from inorganic powder by application of pressure only
    • C23C24/04—Impact or kinetic deposition of particles

Definitions

  • the invention relates to a method for cold gas spraying, in which particles are accelerated for producing layers or molds in a gas jet and impinge on a substrate at high speed, with particles of different sizes injected into a hot gas jet having nozzle inlet temperature and in the hot gas jet a temperature below the melting temperature are heated and the particles are accelerated by relaxation in a nozzle, with the gas jet and particles cool again.
  • a cold gas spray gun comprising a nozzle for accelerating gas jet and particles, which is divided into a convergent nozzle portion and a nozzle outlet, which merge at the nozzle neck, and a powder injection tube, which ends in front of the nozzle throat.
  • a gas in a de Laval nozzle is accelerated to supersonic speed.
  • the coating material is injected as a powder before or after the nozzle throat into the gas jet and accelerated towards the substrate to speeds between 200 and 1600 m / s, preferably between 600 and 1200 m / s.
  • the particles which are brought to high speed, form a dense and firmly adhering layer upon impact. In addition, the particles must deform.
  • Heating the gas jet increases the flow velocity of the gas and thus also the particle velocity. The associated heating of the particles favors deformation on impact.
  • the gas temperature is well below the melting temperature of the coating material, so that melting of the particles in the gas jet can not take place.
  • cold gas spraying eliminates the disadvantages associated with melting, such as oxidation and other phase changes.
  • the method of cold gas spraying includes, for example, the EP 484 533 in which the features of the preamble of independent claims 1 and 5 are disclosed.
  • a method with acceleration close to speeds Sound velocity includes, for example, the DE 101 19 288 ,
  • a Laval nozzle is divided into a convergent section, which ends in the nozzle throat, and in a divergent section beginning at the nozzle throat.
  • a nozzle in which gas is accelerated to near the speed of sound, is divided into a convergent section and an adjoining section, the conical or is cylindrical.
  • An advantage for the layer is when the particles are warm (but not fused) upon impact with the substrate, as this aids in plastic deformation. Melting of the particles can change the properties of the coating to their disadvantage.
  • the gas is heated.
  • the device of EP1 200 200 in which air is used as a carrier gas involves heating the gas before it is passed into the spray gun.
  • the injection of the particles normally takes place axially and centrically in the convergent section of the nozzle by means of a powder injection tube.
  • the transfer of heat from the gas to the spray particles thus takes place substantially in the convergent section and in the region of the nozzle throat.
  • the gas jet cools down again due to the gas relaxation and the associated increase in the speed.
  • the particles cool down again. Since the particles are not all the same size but all sizes up to a maximum value which specifies the particle size, the heat absorption of the particles is very different. Small particles heat up much more easily, but also cool down faster, while larger particles heat up less, but also cool down more slowly. For these reasons, the implementation of particle heating has hitherto only been solved unsatisfactorily, especially in coarser particles, significantly more thermal energy can be stored than is the case with the previously customary processes.
  • the invention has for its object to provide a method and a device
  • the object of the invention is to provide a method and a device which improve the heat absorption of the particles and thereby lead to higher particle temperatures upon impact with the substrate and the use of coarser particles improved.
  • the residence time of the particles is increased in the hot gas jet, so that at least 80 weight percent of the particles reach at least one nozzle inlet temperature, which is 0.7 times the nozzle inlet temperature of the gas jet in Kelvin is.
  • the residence time in the hot gas jet is set such that not only the smaller particles which heat up very quickly reach at least 0.7 times the temperature of the gas jet in Kelvin, but also the larger particles which comparatively warm slowly, reach this temperature.
  • the temperature level of the particles as a whole is increased, without, however, risking a melting of the smaller particles. This is achieved by, on the one hand, setting a gas inlet temperature as a function of the particle properties and preferably below the melting temperature of the particles, and, on the other hand, choosing the dwell time so that the larger particles are also heated to the desired temperature level.
  • the particles are significantly warmer on impact than in the previously customary methods.
  • the temperatures at impact are advantageously around 100 to 400 ° C above the usual temperatures. Warmer particles deform better when they hit the workpiece due to their thermal softening than colder particles.
  • In addition to the kinetic energy is now significantly more thermal energy of the particles for layer formation to disposal. Increasing the available energy leads to an improvement in the adhesion of the particles on the ground and the particles with each other. With the same impact velocity of the particles, the strength and the quality of the layer are consequently significantly improved with the method according to the invention.
  • the particles adhere satisfactorily despite the lower kinetic energy, because the particles have additional energy in the form of heat.
  • the use of powders with larger particle diameters which is possible by the inventive method with simultaneous use of size effects (critical speed for the particle adhesion decreases with increasing particle diameter) increases the efficiency of the cold gas spraying, as coarser powders are cheaper than finer. Coarser particles are also better to convey and less prone to caking in the nozzle.
  • the nozzle inlet temperature of the particles is 0.8 times, preferably 0.9 times, the nozzle inlet temperature of the gas jet.
  • the impacting particles are ductilised by the higher impact temperature and deform better.
  • the binding quality is higher, the layer as a whole is denser and residual stresses are reduced.
  • At least 90 weight percent, preferably at least 95 weight percent of the particles reach the nozzle inlet temperature.
  • the more particles that reach a higher temperature the more energy is available on impact. If according to the invention more particles reach a higher temperature, this means that even the larger particles are heated to higher temperatures. Larger particles have a strong influence on the layer properties, so that the layer properties are greatly improved by the heating of the large particles.
  • coarse-grained powders with simultaneous use of size effects (critical speed for the particle adhesion decreases with increasing particle diameter) to spray acceptable layers, especially in the case of The coarser powders in addition to the kinetic energy, the thermal softening is indispensable for layer formation.
  • particles having a particle size of less than 200 .mu.m, preferably less than 100 .mu.m, more preferably less than 50 microns are used.
  • a limitation of the particle size to a minimum size or the determination of a window for the particle size is not necessary because in the method according to the invention occurring in the powder smaller particles receive a maximum nozzle inlet temperature corresponding to the nozzle inlet temperature of the gas.
  • the nozzle inlet temperature of the gas is due to the process below the melting temperature of the spray material.
  • the object is achieved for the device according to the invention in that the powder injection tube ends more than 40 mm in front of the nozzle throat.
  • the device according to the invention leads to a longer residence time of the spray particles in the hot gas jet and thus has all the aforementioned advantages.
  • the powder injection tube ends 40 to 500 mm, preferably 60 to 400 mm, particularly preferably 80 to 250 mm in front of the nozzle throat. At these intervals, the residence time extension for particle heating is sufficiently high and the cold gas spray gun remains easy to operate.
  • a prechamber is arranged in front of the convergent nozzle section, wherein the powder injection tube ends in the prechamber.
  • the not usual ends of the powder injection tube in the prechamber prolongs the residence time of the particles in the hot gas.
  • the convergent nozzle section is between 20 and 100 mm long.
  • the extension of the residence time of the particles in the hot gas by increasing the distance between Pulverinjetechnischsrohrende and nozzle throat is thus carried out by an extension of the prechamber.
  • a pre-chamber extension is easy to carry out in terms of production, in particular since the hitherto customary nozzle nozzles can continue to be used.
  • the powder injection tube ends in the convergent nozzle section.
  • An extension of the convergent section also increases the residence time in the hot gas jet.
  • nozzle outlet is divergent or cylindrical or conically tapered designed Such nozzle geometries are particularly suitable for cold gas spraying.
  • FIG. 5 shows the development of gas and particle temperature from powder injection to the nozzle exit for a powder injection according to the prior art and the powder injection according to the invention.
  • FIGS. 1 to 4 include a nozzle with a convergent nozzle section 1 and a nozzle outlet 2, an antechamber 3 (with the exception of FIG. 3) and a powder injection tube 4.
  • FIG. 1 shows the previously customary injection of the particles into the nozzle.
  • the nozzle is divided into the convergent nozzle section 1, which merges into the nozzle outlet 2 at the nozzle neck.
  • In front of the convergent nozzle section 1 there is an antechamber 3 into which the gas flows before it enters the nozzle.
  • the powder injection pipe 4 extends beyond the prechamber 3 and terminates in the convergent nozzle section 1.
  • the powder injection pipe end is usually located at a distance of 20 to 30 mm in front of the nozzle throat.
  • the prechamber 3 is configured significantly longer than hitherto usual.
  • the powder injection tube 4 ends already far in front of the pre-chamber 3.
  • the distance between Pulverinjetechnischsrohrende and nozzle throat is thus extended compared to the usual embodiments. With advantage it is now - with unchanged nozzle dimensions - at least 40 mm. Possible is a distance of 500 mm and more. Preferably, the distance between 60 mm and 400 mm, more preferably 80 to 250 mm.
  • FIG 3. Another exemplary embodiment is shown in FIG 3.
  • the convergent tapered nozzle portion 1 is extended compared to the usual embodiments.
  • the powder injection tube 4 ends in the front region of the convergent nozzle section 1.
  • a short prechamber is mounted in front of the convergent nozzle section.
  • the distance between powder injection tube end and nozzle throat achieved by the extension of the convergent section advantageously the values mentioned for the previous example.
  • FIG. 4 shows a further exemplary embodiment.
  • the enlargement of the distance between the powder injection tube end and the nozzle neck is achieved here by an extension of the convergent nozzle section 1 and antechamber 3.
  • the powder injection tube 4 ends in the pre-chamber 3.
  • the aforementioned values are again set up for the distance.
  • the strength of the layer produced increases due to the method according to the invention: when using copper particles of grain size -38 + 10 ⁇ m, the strength of the sprayed copper layer increases from 100 MPa (at 20 mm spacing) to 150 MPa (at 250 mm spacing).
  • FIG. 5 shows the profile of the particle temperature for copper particles with a diameter of 45 ⁇ m.
  • nitrogen was fed into the cold gas spray gun at 30 bar and 600 ° C.
  • the location in m is plotted to the right, the negative values indicating the distances before the nozzle throat and the positive numbers the distances after the nozzle throat in the direction of the nozzle exit.
  • the temperature is given in ° C.
  • the curve C shows the course of the gas temperature:
  • the gas jet passes with a temperature of 580 ° C in the antechamber. In the area of the nozzle neck, the gas begins to cool very quickly due to the relaxation. After the rapid drop, the temperature drop slowly fades.
  • Curve B shows the temperature profile of a particle at an injection 20 mm in front of the nozzle throat.
  • the particle temperature rises up to the nozzle throat to about 230 ° C. After the nozzle throat, the particles cool relatively evenly again and at the nozzle exit, the particle temperature is 180 ° C.
  • the particle injection according to the invention 150 mm before the nozzle throat, the particle temperature rises to the nozzle throat at 480 ° C. After the nozzle throat, the particle temperature drops and at the nozzle outlet it is 340 ° C.
  • the particle temperature at the nozzle outlet increases by 160 ° C.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Nozzles (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

The invention relates to a cold gas spraying pistol in which the powder injection tube (4) terminates more than 40 mm before the nozzle neck, at which the convergent nozzle section (1) transforms into the nozzle outlet (2). By means of the above powder injection at least 80 wt. % of the particles achieve a nozzle inlet temperature which is 0.7 times the nozzle inlet temperature of the gas stream in Kelvin.

Description

Die Erfindung betrifft ein Verfahren zum Kaltgasspritzen, bei welchem Partikel zur Schicht- oder Formherstellung in einem Gasstrahl beschleunigt werden und mit hoher Geschwindigkeit auf ein Substrat auftreffen, wobei Partikel unterschiedlicher Größe in einen heißen, Düsen-Eintrittstemperatur aufweisenden Gasstrahl injiziert und in dem heißen Gasstrahl auf eine Temperatur unterhalb der Schmelztemperatur erwärmt werden und die Partikel durch Entspannung in einer Düse beschleunigt werden, wobei sich Gasstrahl und Partikel wieder abkühlen. Ferner betrifft die Erfindung eine Kaltgasspritzpistole umfassend eine Düse zur Beschleunigung von Gasstrahl und Partikeln, welche sich in eine konvergent zulaufenden Düsenabschnitt und einen Düsenauslauf gliedert, welche am Düsenhals ineinander übergehen, und ein Pulverinjektionsrohr, welches vor dem Düsenhals endet.The invention relates to a method for cold gas spraying, in which particles are accelerated for producing layers or molds in a gas jet and impinge on a substrate at high speed, with particles of different sizes injected into a hot gas jet having nozzle inlet temperature and in the hot gas jet a temperature below the melting temperature are heated and the particles are accelerated by relaxation in a nozzle, with the gas jet and particles cool again. Further, the invention relates to a cold gas spray gun comprising a nozzle for accelerating gas jet and particles, which is divided into a convergent nozzle portion and a nozzle outlet, which merge at the nozzle neck, and a powder injection tube, which ends in front of the nozzle throat.

Beim Kaltgasspritzen wird ein Gas in einer de Lavaldüse auf Überschallgeschwindigkeit beschleunigt. Der Beschichtungswerkstoff wird als Pulver vor oder nach dem Düsenhals in den Gasstrahl injiziert und auf das Substrat hin auf Geschwindigkeiten zwischen 200 und 1600 m/s, vorzugsweise zwischen 600 und 1200 m/s beschleunigt. Die auf hohe Geschwindigkeit gebrachten Partikel bilden beim Aufprall eine dichte und fest haftende Schicht Dazu müssen sich die Partikel verformen. Ein Aufheizen des-Gasstrahls erhöht die Strömungsgeschwindigkeit des Gases und somit auch die Partikelgeschwindigkeit Die damit ebenfalls verbundene Erwärmung der Partikel begünstigt das Verformen beim Aufprall. Die Gastemperatur liegt aber deutlich unterhalb der Schmelztemperatur des Beschichtungswerkstoffs, so dass ein Schmelzen der Partikel im Gasstrahl nicht stattfinden kann. Im Vergleich zu den Verfahren des thermischen Spritzens lassen sich beim Kaltgasspritzen die mit dem Schmelzen verbundenen Nachteile wie Oxidation und andere Phasenumwandlungen vermeiden.In cold gas spraying, a gas in a de Laval nozzle is accelerated to supersonic speed. The coating material is injected as a powder before or after the nozzle throat into the gas jet and accelerated towards the substrate to speeds between 200 and 1600 m / s, preferably between 600 and 1200 m / s. The particles, which are brought to high speed, form a dense and firmly adhering layer upon impact. In addition, the particles must deform. Heating the gas jet increases the flow velocity of the gas and thus also the particle velocity. The associated heating of the particles favors deformation on impact. However, the gas temperature is well below the melting temperature of the coating material, so that melting of the particles in the gas jet can not take place. Compared to thermal spraying, cold gas spraying eliminates the disadvantages associated with melting, such as oxidation and other phase changes.

Das Verfahren des Kaltgasspritzens beinhaltet beispielsweise die EP 484 533 , in der die Merkmale des Oberbegriffs der unabhängigen Ansprüche 1 und 5 offenbart werden. In jüngster Zeit hat sich gezeigt, dass dichte und fest haftende nicht nur dann entstehen, wenn das Gas in einer Lavaldüse auf Überschallgeschwindigkeit sondern auch wenn das Gas nur auf Geschwindigkeiten nahe an der Schallgeschwindigkeit beschleunigt wird. Ein Verfahren mit Beschleunigung auf Geschwindigkeiten nahe der Schallgeschwindigkeit beinhaltet beispielsweise die DE 101 19 288 . Eine Lavaldüse gliedert sich in einen konvergenten Abschnitt, der im Düsenhals endet, und in einen am Düsenhals beginnenden divergenten Abschnitt Eine Düse, in der Gas auf nahezu Schallgeschwindigkeit beschleunigt wird, gliedert sich in einen konvergenten Abschnitt und einen sich daran anschließenden Abschnitt, der konisch oder zylindrisch gestaltet ist.The method of cold gas spraying includes, for example, the EP 484 533 in which the features of the preamble of independent claims 1 and 5 are disclosed. Recently, it has been found that dense and adherent not only arise when the gas in a Laval nozzle is accelerated to supersonic speed but also when the gas is accelerated only at speeds close to the speed of sound. A method with acceleration close to speeds Sound velocity includes, for example, the DE 101 19 288 , A Laval nozzle is divided into a convergent section, which ends in the nozzle throat, and in a divergent section beginning at the nozzle throat. A nozzle in which gas is accelerated to near the speed of sound, is divided into a convergent section and an adjoining section, the conical or is cylindrical.

Von Vorteil für die Schicht ist, wenn die Partikel beim Aufprall auf das Substrat warm (aber nicht angeschmolzen) sind, da dies die plastische Verformung unterstützt. Ein Anschmelzen der Partikel kann die Eigenschaften der Beschichtung zu ihren Ungunsten verändern. Um die Partikeltemperatur anzuheben, wird das Gas erwärmt. In der EP 924 315 ist ein Verfahren beschrieben, bei welchem das Gas bereits direkt nach dem Erfassen des Gaspuffers erwärmt und das erwärmte Gas zur Spritzpistole geleitet wird. Auch die Vorrichtung der EP1 200 200 , in welcher Luft als Trägergas verwendet wird, beinhaltet eine Erwärmung des Gases bevor es in die Spritzpistole geleitet wird. Die Injektion der Partikel erfolgt normalerweise mittels eines Pulverinjektionsrohrs axial und zentrisch in den konvergenten Abschnitt der Düse. Der Übertrag der Wärme vom Gas auf die Spritzpartikel findet folglich im Wesentlichen im konvergenten Abschnitt und im Bereich des Düsenhalses statt. Nach dem Düsenhals kühlt der Gasstrahl aufgrund der Gasentspannung und dem damit verbundenen Anstieg der Geschwindigkeit wieder ab. Sobald die Gastemperatur dabei unter die Partikeltemperatur fällt, kühlen die Partikel wieder ab. Da die Partikel nicht alle die gleiche Größe aufweisen sondern alle Größen bis hin zu einem Maximalwert, welcher die Partikelgröße spezifiziert, ist die Wärmeaufnahme der Partikel sehr unterschiedlich. Kleine Partikel erwärmen sich deutlich leichter, kühlen aber auch schneller wieder ab, während größere Partikel sich schlechter erwärmen, aber auch langsamer wieder abkühlen. Aus diesen Gründen ist die Durchführung der Partikelerwärmung bisher nur unzufriedenstellend gelöst Besonders in gröberen Partikeln kann noch deutlich mehr thermische Energie gespeichert werden als das mit den bisher üblichen Verfahren der Fall ist.An advantage for the layer is when the particles are warm (but not fused) upon impact with the substrate, as this aids in plastic deformation. Melting of the particles can change the properties of the coating to their disadvantage. To raise the particle temperature, the gas is heated. In the EP 924 315 a method is described in which the gas is already heated immediately after the detection of the gas buffer and the heated gas is passed to the spray gun. Also the device of EP1 200 200 in which air is used as a carrier gas, involves heating the gas before it is passed into the spray gun. The injection of the particles normally takes place axially and centrically in the convergent section of the nozzle by means of a powder injection tube. The transfer of heat from the gas to the spray particles thus takes place substantially in the convergent section and in the region of the nozzle throat. After the nozzle throat, the gas jet cools down again due to the gas relaxation and the associated increase in the speed. As soon as the gas temperature falls below the particle temperature, the particles cool down again. Since the particles are not all the same size but all sizes up to a maximum value which specifies the particle size, the heat absorption of the particles is very different. Small particles heat up much more easily, but also cool down faster, while larger particles heat up less, but also cool down more slowly. For these reasons, the implementation of particle heating has hitherto only been solved unsatisfactorily, especially in coarser particles, significantly more thermal energy can be stored than is the case with the previously customary processes.

Zudem hat sich in jüngster Zeit gezeigt, dass die zur Partikelhaftung notwendige kritische Geschwindigkeit bei vielen Spritzwerkstoffen mit größer werdendem Partikeldurchmesser sinkt Dieser-Größeneffekt begünstigt die Verwendung gröberer Partikel im Spritzprozess.In addition, it has recently been shown that the critical velocity required for particle adhesion in many spray materials decreases with increasing particle diameter. This size effect favors the use of coarser particles in the injection process.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung anzuDer Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung anzugeben, die die Wärmeaufnahme der Partikel verbessern und dadurch zu höheren Partikeltemperaturen beim Aufprall auf das Substrat führen und die die Verwendung von gröberen Partikel verbessert.The invention has for its object to provide a method and a device The object of the invention is to provide a method and a device which improve the heat absorption of the particles and thereby lead to higher particle temperatures upon impact with the substrate and the use of coarser particles improved.

Die Aufgabe wird hinsichtlich des Verfahrens erfindungsgemäß dadurch gelöst, dass die Verweildauer der Partikel im heißen Gasstrahl erhöht wird, so dass mindestens 80 Gewichtsprozent der Partikel mindestens eine Düsen-Eintrittstemperatur erreichen, die das 0,7-fache der Düsen-Eintrittstemperatur des Gasstrahls in Kelvin beträgt. Dazu wird bei dem erfindungsgemäßen Verfahren die Verweildauer in dem heißen Gasstrahl derartig eingestellt, dass nicht nur die kleineren Partikel, die sich sehr schnell erwärmen, mindestens die 0,7-fache Temperatur des Gasstrahls in Kelvin erreichen, sondem auch die größeren Partikel die sich vergleichsweise langsam erwärmen, diese Temperatur erreichen. Durch die Erhöhung der Verweildauer erreichen somit nahezu alle Partikel das gewünschte Temperaturniveau. Dadurch wird mit dem erfindungsgemäßen Verfahren der Anteil an Wärmeenergie, der beim Aufprall neben der kinetischen Energie zur Verfügung steht, deutlich erhöht. Dies ist nicht durch eine Erhöhung der Düsen-Eintrittstemperatur des Gasstrahls möglich: Mit einer höheren Gastemperatur würde zwar erreicht, dass die größeren Partikel wärmer würden, aber die kleineren Partikel würden aufschmelzen und die für das Kaltgasspritzen typischen Eigenschaften der Schichten würden sich nicht einstellen. Mit dem erfindungsgemäßen Verfahren hingegen wird das Temperaturniveau der Partikel insgesamt erhöht, ohne jedoch dabei ein Aufschmelzen der kleineren Partikeln zu riskieren. Dies wird erreicht, indem einerseits eine Gaseintrittstemperatur in Abhängigkeit der Partikeleigenschaften und vorzugsweise unterhalb der Schmelztemperatur der Partikel eingestellt wird und anderseits die Verweildauer so lange gewählt wird, dass auch die größeren Partikel auf das gewünschte Temperaturniveau erwärmt werden.The object is achieved in terms of the method according to the invention that the residence time of the particles is increased in the hot gas jet, so that at least 80 weight percent of the particles reach at least one nozzle inlet temperature, which is 0.7 times the nozzle inlet temperature of the gas jet in Kelvin is. For this purpose, in the method according to the invention, the residence time in the hot gas jet is set such that not only the smaller particles which heat up very quickly reach at least 0.7 times the temperature of the gas jet in Kelvin, but also the larger particles which comparatively warm slowly, reach this temperature. By increasing the residence time, almost all particles thus reach the desired temperature level. As a result, with the method according to the invention, the proportion of thermal energy which is available on impact in addition to the kinetic energy is significantly increased. This is not possible by increasing the nozzle inlet temperature of the gas jet: with a higher gas temperature, the larger particles would get warmer, but the smaller particles would melt and the properties of the layers typical of cold gas spraying would not set. By contrast, with the method according to the invention, the temperature level of the particles as a whole is increased, without, however, risking a melting of the smaller particles. This is achieved by, on the one hand, setting a gas inlet temperature as a function of the particle properties and preferably below the melting temperature of the particles, and, on the other hand, choosing the dwell time so that the larger particles are also heated to the desired temperature level.

Mit dem erfindungsgemäßen Verfahren wird also erreicht, dass die Partikel beim Aufprall deutlich wärmer sind als bei den bisher üblichen Verfahren. Die Temperaturen beim Aufprall liegen vorteilhafterweise um 100 bis 400 °C über den bisher üblichen Temperaturen. Wärmere Partikel verformen sich beim Auftreffen auf das Werkstück durch ihre thermische Erweichung besser als kältere Partikel. Neben der kinetischen Energie steht nun deutlich mehr thermische Energie der Partikel zur Schichtausbildung zur Verfügung. Die Erhöhung der zur Verfügung stehenden Energie führt zu einer Verbesserung der Haftung der Partikel auf dem Untergrund und der Partikel untereinander. Bei gleicher Aufprallgeschwindigkeit der Partikel wird folglich mit dem erfindungsgemäßen Verfahren die Festigkeit und die Qualität der Schicht deutlich verbessert. Ist die Aufprallgeschwindigkeit geringer als bisher üblich - etwa durch die Bauart der Düse oder durch Verwendung von Pulvern mit größeren Partikeldurchmessern - haften die Partikel trotz der geringeren kinetischen Energie zufrieden stellend, da den Partikeln zusätzliche Energie in Form von Wärme zur Verfügung steht. Die Verwendung von Pulvern mit größeren Partikeldurchmessern, welche durch das erfindungsgemäße Verfahren unter gleichzeitiger Nutzung von Größeneffekten (kritische Geschwindigkeit für die Partikelhaftung sinkt mit steigendem Partikeldurchmesser) möglich wird, erhöht die Wirtschaftlichkeit des Kaltgasspritzens, da gröbere Pulver günstiger als feinere sind. Gröbere Partikel lassen sich zudem besser fördern und neigen weniger zu Anbackungen in der Düse.With the method according to the invention is thus achieved that the particles are significantly warmer on impact than in the previously customary methods. The temperatures at impact are advantageously around 100 to 400 ° C above the usual temperatures. Warmer particles deform better when they hit the workpiece due to their thermal softening than colder particles. In addition to the kinetic energy is now significantly more thermal energy of the particles for layer formation to disposal. Increasing the available energy leads to an improvement in the adhesion of the particles on the ground and the particles with each other. With the same impact velocity of the particles, the strength and the quality of the layer are consequently significantly improved with the method according to the invention. If the impact velocity is lower than usual - for example due to the design of the nozzle or by using powders with larger particle diameters - the particles adhere satisfactorily despite the lower kinetic energy, because the particles have additional energy in the form of heat. The use of powders with larger particle diameters, which is possible by the inventive method with simultaneous use of size effects (critical speed for the particle adhesion decreases with increasing particle diameter) increases the efficiency of the cold gas spraying, as coarser powders are cheaper than finer. Coarser particles are also better to convey and less prone to caking in the nozzle.

Mit besonderem Vorteil beträgt die Düsen-Eintrittstemperatur der Partikel das 0,8-fache, vorzugsweise das 0,9-fache der Düsen-Eintrittstemperatur des Gasstrahls. Bei höheren Partikeltemperaturen steht beim Aufprall mehr Wärme zur Schichtausbildung zur Verfügung und es zeigen sich die auf das erfindungsgemäße Verfahren zurückzuführenden Verbesserungen der Schichteigenschaften. Die aufprallenden Partikel werden durch die höhere Aufpralltemperatur duktilisiert und verformen sich besser. Die Bindingsqualität ist höher, die Schicht als ganzes ist dichter und Eigenspannungen werden reduziert.With particular advantage, the nozzle inlet temperature of the particles is 0.8 times, preferably 0.9 times, the nozzle inlet temperature of the gas jet. At higher particle temperatures, more heat is available for layer formation on impact, and the improvements in layer properties attributable to the process according to the invention are evident. The impacting particles are ductilised by the higher impact temperature and deform better. The binding quality is higher, the layer as a whole is denser and residual stresses are reduced.

Vorteilhafterweise erreichen mindestens 90 Gewichtsprozent, vorzugsweise mindestens 95 Gewichtsprozent der Partikel die Düsen-Eintrittstemperatur. Je mehr Partikel eine höhere Temperatur erreichen, desto mehr Energie steht beim Aufprall zur Verfügung. Wenn erfindungsgemäß mehr Partikel eine höhere Temperatur erreichen, bedeutet dies, dass auch die größeren Partikel auf höhere Temperaturen erwärmt werden. Größere Partikel haben einen starken Einfluss auf die Schichteigenschaften, so dass sich die Schichteigenschaften durch die Erwärmung der großen Partikel stark verbessern. Auch wird es möglich, mit grobkömigeren Pulvern unter gleichzeitiger Nutzung von Größeneffekten (kritische Geschwindigkeit für die Partikelhaftung sinkt mit steigendem Partikeldurchmesser) akzeptable Schichten zu spritzen, da besonders bei den gröberen Pulvern neben der kinetischen Energie die thermische Erweichung zur Schichtausbildung unabdingbar ist.Advantageously, at least 90 weight percent, preferably at least 95 weight percent of the particles reach the nozzle inlet temperature. The more particles that reach a higher temperature, the more energy is available on impact. If according to the invention more particles reach a higher temperature, this means that even the larger particles are heated to higher temperatures. Larger particles have a strong influence on the layer properties, so that the layer properties are greatly improved by the heating of the large particles. It is also possible to use coarse-grained powders with simultaneous use of size effects (critical speed for the particle adhesion decreases with increasing particle diameter) to spray acceptable layers, especially in the case of The coarser powders in addition to the kinetic energy, the thermal softening is indispensable for layer formation.

In vorteilhafter Ausgestaltung der Erfindung werden Partikel mit einer Partikelgröße von kleiner 200 µm, vorzugsweise von kleiner 100 µm, besonders bevorzugt von kleiner 50 µm verwendet. Eine Begrenzung der Partikelgröße auf eine Minimalgröße oder die Festlegung eines Fensters für die Partikelgröße ist nicht notwendig, da bei dem erfindungsgemäßen Verfahren die in dem Pulver vorkommenden kleineren Partikel maximal eine Düsen-Eintrittstemperatur erhalten, die der Düsen-Eintrittstemperatur des Gases entspricht. Die Düsen-Eintrittstemperatur des Gases liegt verfahrensbedingt unter der Schmelztemperatur des Spritzwerkstoffes.In an advantageous embodiment of the invention, particles having a particle size of less than 200 .mu.m, preferably less than 100 .mu.m, more preferably less than 50 microns are used. A limitation of the particle size to a minimum size or the determination of a window for the particle size is not necessary because in the method according to the invention occurring in the powder smaller particles receive a maximum nozzle inlet temperature corresponding to the nozzle inlet temperature of the gas. The nozzle inlet temperature of the gas is due to the process below the melting temperature of the spray material.

Die Aufgabe wird für die Vorrichtung erfindungsgemäß dadurch gelöst, dass das Pulverinjektionsrohr mehr als 40 mm vor dem Düsenhals endet. Die erfindungsgemäße Vorrichtung führt zu einer längeren Verweildauer der Spritzpartikel in dem heißen Gasstrahl und weist somit alle vorgenannten Vorteile auf.The object is achieved for the device according to the invention in that the powder injection tube ends more than 40 mm in front of the nozzle throat. The device according to the invention leads to a longer residence time of the spray particles in the hot gas jet and thus has all the aforementioned advantages.

Vorteilhafterweise endet das Pulverinjektionsrohr 40 bis 500 mm, vorzugsweise 60 bis 400 mm, besonders bevorzugt 80 bis 250 mm vor dem Düsenhals. Bei diesen Abständen ist die Verweildauerverlängerung zur Partikelerwärmung genügend groß und die Kaltgasspritzpistole bleibt in der Bedienung handlich.Advantageously, the powder injection tube ends 40 to 500 mm, preferably 60 to 400 mm, particularly preferably 80 to 250 mm in front of the nozzle throat. At these intervals, the residence time extension for particle heating is sufficiently high and the cold gas spray gun remains easy to operate.

In einer vorteilhaften Ausgestaltung der Erfindung ist vor dem konvergenten Düsenabschnitt eine Vorkammer angeordnet, wobei das Pulverinjektionsrohr in der Vorkammer endet Durch das bisher nicht übliche Enden des Pulverinjektionsrohrs in der Vorkammer verlängert sich die Verweildauer der Partikel in dem heißen Gas.In an advantageous embodiment of the invention, a prechamber is arranged in front of the convergent nozzle section, wherein the powder injection tube ends in the prechamber. The not usual ends of the powder injection tube in the prechamber prolongs the residence time of the particles in the hot gas.

Vorteilhafterweise ist dabei der konvergente Düsenabschnitt zwischen 20 und 100 mm lang. Die Verlängerung der Verweildauer der Partikel in dem heißen-Gas durch die Vergrößerung des Abstands zwischen Pulverinjektionsrohrende und Düsenhals erfolgt somit durch eine Verlängerung der Vorkammer. Eine Vorkammerverlängerung ist fertigungstechnisch leicht durchzuführen, Insbesondere da die bisher üblichen Düsen- weiterhin verwendet werden können.Advantageously, the convergent nozzle section is between 20 and 100 mm long. The extension of the residence time of the particles in the hot gas by increasing the distance between Pulverinjektionsrohrende and nozzle throat is thus carried out by an extension of the prechamber. A pre-chamber extension is easy to carry out in terms of production, in particular since the hitherto customary nozzle nozzles can continue to be used.

In einer anderen vorteilhaften Ausgestaltung der Erfindung endet das Pulverinjektionsrohr im konvergenten Düsenabschnitt. Auch eine Verlängerung des konvergenten Abschnitts erhöht die Verweildauer im heißen Gasstrahl.In another advantageous embodiment of the invention, the powder injection tube ends in the convergent nozzle section. An extension of the convergent section also increases the residence time in the hot gas jet.

In vorteilhafter Ausgestaltung ist der Düsenauslauf divergierend oder zylindrisch oder konisch zulaufend gestaltet Derartige Düsengeometrien eignen sich in besonderer Weise zum Kaltgasspritzen.In an advantageous embodiment of the nozzle outlet is divergent or cylindrical or conically tapered designed Such nozzle geometries are particularly suitable for cold gas spraying.

Im Folgenden wird zunächst eine Düse mit Pulverinjektion nach dem Stand der Technik und anschließend die Erfindung anhand von drei beispielhaften Ausgestaltungen näher erläutert. Hierzu zeigt

Figur 1
eine Düse mit Pulverinjektion nach dem Stand der Technik,
Figur 2
eine beispielhafte Ausgestaltung der Erfindung mit verlängerter Vorkammer,
Figur 3
eine andere beispielhafte Ausgestaltung mit verlängertem konvergent zulaufenden Düsenabschnitt und
Figur 4
eine dritte beispielhafte Ausgestaltung verlängerter Vorkammer und verlängertem konvergenten Düsenabschnitt.
In the following, a nozzle with powder injection according to the prior art and then the invention will be explained in more detail with reference to three exemplary embodiments. This shows
FIG. 1
a nozzle with powder injection according to the prior art,
FIG. 2
an exemplary embodiment of the invention with extended prechamber,
FIG. 3
another exemplary embodiment with extended convergent nozzle portion and
FIG. 4
a third exemplary embodiment of extended prechamber and extended convergent nozzle portion.

Weiterhin zeigt Figur 5 die Entwicklung von Gas- und Partikeltemperatur von der Pulverinjektion ab bis zum Düsenaustritt für eine Pulverinjektion nach dem Stand der Technik und die erfindungsgemäße Pulverinjektion.Furthermore, FIG. 5 shows the development of gas and particle temperature from powder injection to the nozzle exit for a powder injection according to the prior art and the powder injection according to the invention.

Figur 1 bis 4 beinhalten eine Düse mit einem konvergenten Düsenabschnitt 1 und einem Düsenauslauf 2, eine Vorkammer 3 (mit Ausnahme von Figur 3) und ein Pulverinjektionsrohr 4.FIGS. 1 to 4 include a nozzle with a convergent nozzle section 1 and a nozzle outlet 2, an antechamber 3 (with the exception of FIG. 3) and a powder injection tube 4.

Figur 1 zeigt die bisher übliche Injektion der Partikel in die Düse. Die Düse gliedert sich in den konvergenten Düsenabschnitt 1, der am Düsenhals in den Düsenauslauf 2 übergeht. Vor dem konvergenten Düsenabschnitt 1 befindet sich eine Vorkammer 3, in welche das Gas strömt bevor es in die Düse gelangt. Das Pulverinjektionsrohr 4 reicht über die Vorkammer 3 hinaus und endet in dem konvergenten Düsenabschnitt 1. Das Pulverinjektionsrohrende befindet sich üblicherweise in einem Abstand von 20 bis 30 mm vor dem Düsenhals.FIG. 1 shows the previously customary injection of the particles into the nozzle. The nozzle is divided into the convergent nozzle section 1, which merges into the nozzle outlet 2 at the nozzle neck. In front of the convergent nozzle section 1 there is an antechamber 3 into which the gas flows before it enters the nozzle. The powder injection pipe 4 extends beyond the prechamber 3 and terminates in the convergent nozzle section 1. The powder injection pipe end is usually located at a distance of 20 to 30 mm in front of the nozzle throat.

In der beispielhaften Ausgestaltung gemäß Figur 2 ist die Vorkammer 3 deutlich länger ausgestaltet als bisher üblich. Das Pulverinjektionsrohr 4 endet bereits weit vorne in der Vorkammer 3. Der Abstand zwischen Pulverinjektionsrohrende und Düsenhals ist damit gegenüber den bisher üblichen Ausgestaltungen verlängert. Mit Vorteil beträgt er nun - bei unveränderten Düsenabmessungen - mindestens 40 mm. Möglich ist ein Abstand von 500 mm und mehr. Vorzugsweise beträgt der Abstand zwischen 60 mm und 400 mm, besonders bevorzugt 80 bis 250 mm.In the exemplary embodiment according to FIG. 2, the prechamber 3 is configured significantly longer than hitherto usual. The powder injection tube 4 ends already far in front of the pre-chamber 3. The distance between Pulverinjektionsrohrende and nozzle throat is thus extended compared to the usual embodiments. With advantage it is now - with unchanged nozzle dimensions - at least 40 mm. Possible is a distance of 500 mm and more. Preferably, the distance between 60 mm and 400 mm, more preferably 80 to 250 mm.

Eine andere beispielhafte Ausgestaltung zeigt Figur 3. Hier ist der konvergent zulaufende Düsenabschnitt 1 gegenüber den bisher üblichen Ausgestaltungen verlängert. Das Pulverinjektionsrohr 4 endet im vorderen Bereich des konvergenten Düsenabschnitts 1. Eventuell ist vor dem konvergenten Düsenabschnitt eine kurze Vorkammer angebracht. Der Abstand zwischen Pulverinjektionsrohrende und Düsenhals erreicht durch die Verlängerung des konvergenten Abschnitts vorteilhafterweise die für das vorherige Beispiel genannten Werte.Another exemplary embodiment is shown in FIG 3. Here, the convergent tapered nozzle portion 1 is extended compared to the usual embodiments. The powder injection tube 4 ends in the front region of the convergent nozzle section 1. Possibly, a short prechamber is mounted in front of the convergent nozzle section. The distance between powder injection tube end and nozzle throat achieved by the extension of the convergent section advantageously the values mentioned for the previous example.

In Figur 4 ist eine weitere beispielhafte Ausgestaltung gezeigt Die Vergrößerung des Abstands Pulverinjektionsrohrende - Düsenhals wird hier durch eine Verlängerung des konvergenten Düsenabschnitts 1 und Vorkammer 3 erreicht. Das Pulverinjektionsrohr 4 endet in der Vorkammer 3. Vorteilhafterweise werden für den Abstand wiederum die vorgenannten Werte eingerichtet.FIG. 4 shows a further exemplary embodiment. The enlargement of the distance between the powder injection tube end and the nozzle neck is achieved here by an extension of the convergent nozzle section 1 and antechamber 3. The powder injection tube 4 ends in the pre-chamber 3. Advantageously, the aforementioned values are again set up for the distance.

Für alle beispielhaften Ausgestaltungen (Figur 2 bis 4) ist eine thermische Isolierung der Vorkammer und des konvergenten Düsenabschnittes anzustreben, um unnötige Wärmeverluste zu vermeiden und die thermische Belastung tragender Bauteile zu minimieren.For all exemplary embodiments (Figure 2 to 4), a thermal isolation of the pre-chamber and the convergent nozzle portion to aim in order to avoid unnecessary heat loss and to minimize the thermal load-bearing components.

Bei den bisher üblichen Verfahren mit einer Pulverinjektion 20 mm vor dem Düsenhals wird bei der Verwendung von Stickstoff für den Gasstrahl bei einem Gasdruck von 30 bar und einer Gastemperatur von 600 °C vor Düseneintritt für ein Partikel mit 5 µm Durchmesser beim Aufprall eine Temperatur von nur 50 °C erreicht während ein Partikel mit 50 µm Durchmesser beim Aufprall eine Temperatur von 175 °C aufweist. Bei der erfindungsgemäßen frühen Partikelinjektion treffen die Partikel bei gleichen Prozessparametem und sonst unveränderten Düsenabmessungen mit deutlich höheren Temperaturen auf das Substrat. Erfolgt die Partikelinjektion 80 mm vor dem Düsenhals, weist ein Partikel mit 50 µm Durchmesser beim Aufprall eine Temperatur von 280 °C auf und bei einer Partikelinjektion 150 µm vor dem Düsenhals gar eine Temperatur von 340 °C. Durch das erfindungsgemäße Verfahren steigt u.a. die Festigkeit der erzeugten Schicht an: bei Verwendung von Kupferpartikeln der Körnung -38+10 µm steigt die Festigkeit der gespritzten Kupferschicht von 100 MPa (bei 20 mm Abstand) auf 150 MPa (bei 250 mm Abstand) an.In the conventional method with a powder injection 20 mm in front of the nozzle neck when using nitrogen for the gas jet at a gas pressure of 30 bar and a gas temperature of 600 ° C before nozzle entry for a particle with 5 micron diameter on impact a temperature of only 50 ° C reached while a particle with a diameter of 50 microns at impact a temperature of 175 ° C. In the case of the early particle injection according to the invention, the particles meet with significantly higher process parameters and otherwise unchanged nozzle dimensions Temperatures on the substrate. If the particle injection takes place 80 mm in front of the nozzle throat, a particle with a diameter of 50 μm has a temperature of 280 ° C. on impact and even a temperature of 340 ° C. with a particle injection of 150 μm in front of the nozzle throat. Among other things, the strength of the layer produced increases due to the method according to the invention: when using copper particles of grain size -38 + 10 μm, the strength of the sprayed copper layer increases from 100 MPa (at 20 mm spacing) to 150 MPa (at 250 mm spacing).

In Figur 5 ist der Verlauf der Partikeltemperatur für Kupferpartikel mit einem Durchmesser von 45 µm dargestellt. Für den Gasstrahl wurde Stickstoff bei 30 bar und 600 °C in die Kaltgasspritzpistole geleitet. In dem Diagramm ist nach rechts der Ort in m aufgetragen, wobei die negativen Werte die Abstände vor dem Düsenhals und die positiven Zahlen die Abstände nach dem Düsenhals in Richtung Düsenaustritt angegeben. Nach oben ist die Temperatur in °C angegeben. Die Kurve C zeigt den Verlauf der Gastemperatur: Der Gasstrahl gelangt mit einer Temperatur von 580°C in die Vorkammer. Im Bereich des Düsenhalses beginnt das Gas aufgrund der Entspannung sehr schnell abzukühlen. Nach dem schnellen Abfall klingt der Temperaturabfall langsam aus. Kurve B zeigt den Temperaturverlauf eines Partikels bei einer Injektion 20 mm vor dem Düsenhals. Die Partikeltemperatur steigt bis hin zum Düsenhals auf ca. 230 °C an. Nach dem Düsenhals kühlen die Partikel relativ gleichmäßig wieder ab und bei Düsenaustritt liegt die Partikeltemperatur bei 180 °C. Erfolgt die Partikelinjektion erfindungsgemäß 150 mm vor dem Düsenhals steigt die Partikeltemperatur bis zum Düsenhals auf 480 °C an. Nach dem Düsenhals sinkt die Partikeltemperatur ab und beim Düsenaustritt beträgt sie 340 °C. Durch die Verlegung des Injektionsorts von 20 mm auf 150 mm vor Düsenhals steigt somit die Partikeltemperatur beim Düsenaustritt um 160 °C an.FIG. 5 shows the profile of the particle temperature for copper particles with a diameter of 45 μm. For the gas jet, nitrogen was fed into the cold gas spray gun at 30 bar and 600 ° C. In the diagram, the location in m is plotted to the right, the negative values indicating the distances before the nozzle throat and the positive numbers the distances after the nozzle throat in the direction of the nozzle exit. At the top, the temperature is given in ° C. The curve C shows the course of the gas temperature: The gas jet passes with a temperature of 580 ° C in the antechamber. In the area of the nozzle neck, the gas begins to cool very quickly due to the relaxation. After the rapid drop, the temperature drop slowly fades. Curve B shows the temperature profile of a particle at an injection 20 mm in front of the nozzle throat. The particle temperature rises up to the nozzle throat to about 230 ° C. After the nozzle throat, the particles cool relatively evenly again and at the nozzle exit, the particle temperature is 180 ° C. If the particle injection according to the invention 150 mm before the nozzle throat, the particle temperature rises to the nozzle throat at 480 ° C. After the nozzle throat, the particle temperature drops and at the nozzle outlet it is 340 ° C. By moving the injection location from 20 mm to 150 mm in front of the nozzle throat, the particle temperature at the nozzle outlet increases by 160 ° C.

BezugszeichenlisteLIST OF REFERENCE NUMBERS

11
konvergenter Düsenabschnittconvergent nozzle section
22
Düsenauslaufnozzle outlet
33
Vorkammerantechamber
44
PulverinjektionsrohrPowder injection tube

Claims (10)

  1. Method of cold-gas spraying in which particles for producing a layer or form are accelerated in a gas jet and impinge on a substrate at high speed, particles of different sizes being injected into a hot gas jet at nozzle inlet temperature (4) and heated in the hot gas jet to a temperature below the melting temperature, and the particles being accelerated by expansion in a nozzle (1, 2), the gas jet and the particles cooling down again, characterized in that the residence time of the particles in the hot gas jet is increased, so that at least 80 percent by weight of the particles reach at least a nozzle inlet temperature that is 0.7 of the nozzle inlet temperature of the gas jet in Kelvins.
  2. Method according to Claim 1, characterized in that the nozzle inlet temperature of the particles is 0.8, preferably 0.9, thereof.
  3. Method according to Claim 1 or 2, characterized in that at least 90 percent by weight, preferably 95 percent by weight, of the particles reach the nozzle inlet temperature.
  4. Method according to one of Claims 1 to 3, characterized in that particles with a particle size of less than 200 µm, preferably less than 100 µm, with particular preference less than 50 µm, are used.
  5. Cold-gas spray gun comprising a nozzle for accelerating a gas jet and particles, which is divided into a convergently tapering nozzle portion (1) and a nozzle outlet (2), which merge one into the other at the nozzle neck, and a powder injection tube (4), which ends upstream of the nozzle neck, characterized in that the powder injection tube (4) ends over 40 mm upstream of the nozzle neck.
  6. Cold-gas spray gun according to Claim 5, characterized in that the powder injection tube ends 40 to 500 mm, preferably 60 to 400 mm, with particular preference 80 to 250 mm, upstream of the nozzle neck.
  7. Cold-gas spray gun according to Claim 5 or 6, characterized in that a pre-chamber (3) is arranged upstream of the convergent nozzle portion (1), the powder injection tube (4) ending in the pre-chamber (3).
  8. Cold-gas spray gun according to Claim 7, characterized in that the convergent nozzle portion (1) is between 20 and 100 mm long.
  9. Cold-gas spray gun according to Claim 5 or 6, characterized in that the powder injection tube (4) ends in the convergent nozzle portion (1).
  10. Cold-gas spray gun according to one of Claims 5 to 9, characterized in that the nozzle outlet (2) is formed in a divergently or cylindrically or conically tapering manner.
EP05785200A 2004-09-24 2005-09-09 Method for cold gas spraying and cold gas spraying pistol with increased retention time for the powder in the gas stream Not-in-force EP1791645B1 (en)

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DE102004046348 2004-09-24
DE102005004116A DE102005004116A1 (en) 2004-09-24 2005-01-28 Method for cold gas spraying and cold gas spray gun
PCT/EP2005/009705 WO2006034778A1 (en) 2004-09-24 2005-09-09 Method for cold gas spraying and cold gas spraying pistol with increased retention time for the powder in the gas stream

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EP1791645B1 true EP1791645B1 (en) 2007-12-12

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DE102012000816A1 (en) 2012-01-17 2013-07-18 Linde Aktiengesellschaft Method and device for thermal spraying
US11662300B2 (en) 2019-09-19 2023-05-30 Westinghouse Electric Company Llc Apparatus for performing in-situ adhesion test of cold spray deposits and method of employing
US11898986B2 (en) 2012-10-10 2024-02-13 Westinghouse Electric Company Llc Systems and methods for steam generator tube analysis for detection of tube degradation
US11935662B2 (en) 2019-07-02 2024-03-19 Westinghouse Electric Company Llc Elongate SiC fuel elements

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DE102006014124A1 (en) 2006-03-24 2007-09-27 Linde Ag Cold spray gun
DE102007001477B3 (en) 2007-01-09 2008-01-31 Siemens Ag Cold gas spraying method for spraying the surface of a turbine blade comprises injecting particles of a first type in a first region of a stagnation chamber which lies closer to a nozzle than a second region
DE102007009600A1 (en) 2007-02-26 2008-08-28 Linde Ag Thermal or spray process to apply a powder coating to the poorly accessible surface of a component via curved baffle deflector
DE102007032022A1 (en) 2007-07-10 2009-01-15 Linde Ag Kaltgasspritzdüse
DE102007032021A1 (en) 2007-07-10 2009-01-15 Linde Ag Kaltgasspritzdüse
DE102012001361A1 (en) 2012-01-24 2013-07-25 Linde Aktiengesellschaft Method for cold gas spraying

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US6502767B2 (en) * 2000-05-03 2003-01-07 Asb Industries Advanced cold spray system
US20020073982A1 (en) * 2000-12-16 2002-06-20 Shaikh Furqan Zafar Gas-dynamic cold spray lining for aluminum engine block cylinders
US6623796B1 (en) * 2002-04-05 2003-09-23 Delphi Technologies, Inc. Method of producing a coating using a kinetic spray process with large particles and nozzles for the same
CA2433613A1 (en) * 2002-08-13 2004-02-13 Russel J. Ruprecht, Jr. Spray method for mcralx coating

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DE102012000816A1 (en) 2012-01-17 2013-07-18 Linde Aktiengesellschaft Method and device for thermal spraying
EP2617868A1 (en) 2012-01-17 2013-07-24 Linde Aktiengesellschaft Method and device for thermal spraying
US11898986B2 (en) 2012-10-10 2024-02-13 Westinghouse Electric Company Llc Systems and methods for steam generator tube analysis for detection of tube degradation
US11935662B2 (en) 2019-07-02 2024-03-19 Westinghouse Electric Company Llc Elongate SiC fuel elements
US11662300B2 (en) 2019-09-19 2023-05-30 Westinghouse Electric Company Llc Apparatus for performing in-situ adhesion test of cold spray deposits and method of employing

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DE102005004116A1 (en) 2006-04-06
EP1791645A1 (en) 2007-06-06
ATE380599T1 (en) 2007-12-15
ES2297754T3 (en) 2008-05-01
DE502005002252D1 (en) 2008-01-24

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