EP1985722B1 - Plasma spray method for coating excess heat tubes - Google Patents

Plasma spray method for coating excess heat tubes Download PDF

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Publication number
EP1985722B1
EP1985722B1 EP08004327A EP08004327A EP1985722B1 EP 1985722 B1 EP1985722 B1 EP 1985722B1 EP 08004327 A EP08004327 A EP 08004327A EP 08004327 A EP08004327 A EP 08004327A EP 1985722 B1 EP1985722 B1 EP 1985722B1
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EP
European Patent Office
Prior art keywords
protective layer
spraying method
thermal spraying
self
metal alloy
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EP08004327A
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German (de)
French (fr)
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EP1985722A2 (en
EP1985722A3 (en
Inventor
Bodo Häuser
Hendrik Häuser
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Hauser&co GmbH
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Hauser&co GmbH
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Priority to PL08004327T priority Critical patent/PL1985722T3/en
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Publication of EP1985722A3 publication Critical patent/EP1985722A3/en
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Classifications

    • 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
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • 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
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C23C4/067—Metallic material containing free particles of non-metal elements, e.g. carbon, silicon, boron, phosphorus or arsenic
    • 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
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/18—After-treatment

Definitions

  • the invention relates to a thermal spraying method for producing a protective layer on hot gases, in particular flue gases acted upon metallic walls, preferably of boiler tubes, in which a powder is applied to the previously treated metallic walls to form the protective layer.
  • the materials to be coated eg steel materials.
  • the workpiece to be coated is first cleaned and then blasted with corundum or the like.
  • a preheating of the base material to a temperature of 150 ° C to 250 ° C before blasting is often necessary, said preheating temperature is recommended in particular in the flame spraying with self-fluxing powders.
  • the coating materials have a melting point below the melting temperature of the material to be coated, and are melted after spraying in the base material.
  • the protective layer has a relatively large layer thickness of up to 2 mm at relatively high porosity of 15 to 20% before melting. These factors cause meltdown.
  • the melting is usually carried out with a hard acetylene-oxygen flame, so that the protective layer to a temperature (such as in EP 0 223 135 ) is heated up to 1200 ° C.
  • a temperature such as in EP 0 223 135
  • the layer thickness increases about 20 percent by volume, which disadvantageously forms a diffusion layer, ie elements of the protective layer diffuse due to the heat load in the base material.
  • a diffusive composite of the protective layer is achieved with the base material.
  • high-temperature steels such as 15Mo3, 13CrMo45 or 10CrMo910, the high heat input leads to a disadvantageous microstructure change.
  • plasma spraying processes for producing the protective layer are also known, for example in US Pat DE 42 20 063 C1 disclosed. That in the DE 42 20 063 C1 The disclosed method has proven itself in practice to the effect that the distortion of workpieces and crack-forming stresses in the base material are avoided.
  • the invention has for its object to improve a thermal spraying process of the type mentioned with simple means so that at lower heat input into the base material a closed, melted in itself protective layer is achieved without diffusive compound with the base material.
  • the object is achieved by a plasma spraying process according to claim 1, in which a self-flowing metal alloy of coarse grain size is sprayed onto the metallic walls as powder, the protective layer being melted after spraying.
  • the invention is based on the finding that the temperature of the base material in the plasma spraying process is basically only slightly increased, since the plasma jet itself does not even reach the base material.
  • the invention proceeds by using a coarse-grained powder as the coating material or filler material in the plasma spraying process according to the invention, wherein instead of the high thermal melting, only a melting of the protective layer is carried out at much lower temperatures and thus significantly lower thermal loads are introduced into the base material ,
  • the powder or the self-flowing metal alloy has a grain size of 90 to 180 .mu.m, wherein the protective layer after spraying has a layer thickness of 0.2 to 1 mm, preferably 0.3 to 0.6 mm.
  • the porosity of the protective layer before melting is 0.5 to 3%.
  • a self-fluxing metal alloy is used as powder, which has at least the following constituents: 77.35 wt .-% Ni; 11.5% by weight Cr; 0.65% by weight C; 2.5% by weight B; 3.75% by weight of Si; 4.25% by weight of Fe.
  • the protective layer has a hardness of 48 to 52 HRC after melting.
  • the workpiece preferably a tube with electrofused corundum or the like, is blasted.
  • the powder or the self-flowing metal alloy is heated to about 25 ° C. before the injection process.
  • the melting of the protective layer after spraying is carried out expediently with a neutral flame (acetylene / oxygen), wherein the protective layer compared to the melting to a much lower Temperature of about 800 ° C is heated, which advantageously avoids a diffusive composite of the protective layer to the base material. But this also structural changes of the base material are avoided, which is why the plasma spraying process according to the invention can also be applied to critical materials such as 15Mo3, 10CrMo910 or 13CrMo45.
  • the melted protective layer cools down very quickly, which also positively influences the formation of a closed, hard shell (protective layer).
  • the workpiece or the coated tube to cool in air.
  • the plasma spraying process according to the invention is particularly suitable for use on superheater pipes in waste incineration plants, without restricting the application thereof.
  • waste incineration plants it has been found that pure sprayed coatings as protective layers, although the normal operation meet; However, a required cleaning process (blasting process) often leads to damage, which ultimately causes the failure of the protective layer.
  • a compact, gas-tight, firmly bonded to the base material protective layer is generated, which also resists a blasting process, since the diffusion layer or a structural change of the base material is avoided.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating By Spraying Or Casting (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

Thermal spraying process for producing protective coatings on fire tubes uses a self-flowing alloy powder with large particles which is fused after spraying on to the tubes. An independent claim is included for use of self-flowing alloy powders with large particles in thermal spraying to produce protective coatings on fire tubes.

Description

Die Erfindung betrifft ein thermisches Spritzverfahren zum Herstellen einer Schutzschicht auf mit heißen Gasen, insbesondere Rauchgasen beaufschlagten metallischen Wänden vorzugsweise von Kesselrohren, bei dem ein Pulver auf die zuvor behandelten metallischen Wände zur Bildung der Schutzschicht aufgetragen wird.The invention relates to a thermal spraying method for producing a protective layer on hot gases, in particular flue gases acted upon metallic walls, preferably of boiler tubes, in which a powder is applied to the previously treated metallic walls to form the protective layer.

In Kraftwerken, insbesondere in Müllverbrennungsanlagen bzw. deren Überhitzerkesseln herrscht eine sehr aggressive, korrosive Umgebung aufgrund der sehr spezifischen Zusammensetzung des Brennstoffs (Abfall). Die Wände der Kessel, aber auch Rohrbündel bzw. Überhitzerrohrbündel müssen daher insbesondere gegen Varianten der Hochtemperaturkorrosion geschützt werden. Aus einer Vielzahl von Schutzmaßnahmen gegen Hochtemperaturkorrosion und Verschleiß ist zum Beispiel das thermische Spritzen, beispielsweise als Flammspritzen oder auch als Plasmaspritzverfahren bekanntIn power plants, especially in waste incineration plants or their superheater boilers, there is a very aggressive, corrosive environment due to the very specific composition of the fuel (waste). The walls of the boiler, but also tube bundles or superheater tube bundles must therefore be protected in particular against variants of high-temperature corrosion. From a variety of protective measures against high temperature corrosion and wear, for example, the thermal spraying, for example as flame spraying or as a plasma spraying known

Mittels des Flammspritzens werden Pulver als Beschichtungswerkstoff auf die zu beschichtenden Werkstoffe, z.B. Stahlwerkstoffe aufgebracht. Hierzu wird das zu beschichtende Werkstück zunächst gereinigt und anschließend mit Korund oder dergleichen gestrahlt. Eine Vorwärmung des Grundwerkstoffs auf eine Temperatur von 150°C bis 250°C vor dem Strahlen ist oft notwendig, wobei die genannte Vorwärmtemperatur insbesondere bei dem Flammspritzen mit selbstfließenden Pulvern empfohlen wird. Die Beschichtungswerkstoffe weisen einen Schmelzpunkt unterhalb der Schmelztemperatur des zu beschichtenden Werkstoffs auf, und werden nach dem Aufspritzen in den Grundwerkstoff eingeschmolzen. Die Schutzschicht weist vor dem Einschmelzen eine relativ große Schichtdicke von bis zu 2 mm bei relativ hoher Porosität von 15 bis 20 % auf. Diese Faktoren bedingen das Einschmelzen. Das Einschmelzen wird üblicherweise mit einer harten Acetylen-Sauerstoffflamme durchgeführt, so dass die Schutzschicht auf eine Temperatur (wie z.B. in EP 0 223 135 ) von bis zu 1200°C erwärmt wird. Durch dieses Einschmelzen nimmt die Schichtdicke um ca. 20 Volumenprozent ab, wobei sich nachteiliger Weise eine Diffusionsschicht bildet, d.h. Elemente der Schutzschicht diffundieren aufgrund der Wärmebelastung in den Grundwerkstoff. Somit wird ein diffusiver Verbund der Schutzschicht mit dem Grundwerkstoff erreicht. Insbesondere bei Warmfesten Stählen wie z.B. aus dem Werkstoff 15Mo3, 13CrMo45 oder 10CrMo910 führt der hohe Wärmeeintrag zu einer nachteiligen Gefügeänderung.By means of flame spraying, powders are applied as coating material to the materials to be coated, eg steel materials. For this purpose, the workpiece to be coated is first cleaned and then blasted with corundum or the like. A preheating of the base material to a temperature of 150 ° C to 250 ° C before blasting is often necessary, said preheating temperature is recommended in particular in the flame spraying with self-fluxing powders. The coating materials have a melting point below the melting temperature of the material to be coated, and are melted after spraying in the base material. The protective layer has a relatively large layer thickness of up to 2 mm at relatively high porosity of 15 to 20% before melting. These factors cause meltdown. The melting is usually carried out with a hard acetylene-oxygen flame, so that the protective layer to a temperature (such as in EP 0 223 135 ) is heated up to 1200 ° C. By this melting, the layer thickness increases about 20 percent by volume, which disadvantageously forms a diffusion layer, ie elements of the protective layer diffuse due to the heat load in the base material. Thus, a diffusive composite of the protective layer is achieved with the base material. Particularly in the case of high-temperature steels such as 15Mo3, 13CrMo45 or 10CrMo910, the high heat input leads to a disadvantageous microstructure change.

Bekannt sind aber auch Plasmaspritzverfahren zur Herstellung der Schutzschicht, wie beispielsweise in der DE 42 20 063 C1 offenbart. Das in der DE 42 20 063 C1 offenbarte Verfahren hat sich in der Praxis dahingehend bewährt als der Verzug von Werkstücken und rißbildende Spannungen im Grundwerkstoff vermieden werden.However, plasma spraying processes for producing the protective layer are also known, for example in US Pat DE 42 20 063 C1 disclosed. That in the DE 42 20 063 C1 The disclosed method has proven itself in practice to the effect that the distortion of workpieces and crack-forming stresses in the base material are avoided.

Der Erfindung liegt die Aufgabe zugrunde, ein thermisches Spritzverfahren der Eingangs genannten Art mit einfachen Mittel so zu verbessern, dass bei geringerer Wärmeeinbringung in den Grundwerkstoff eine geschlossene, in sich eingeschmolzene Schutzschicht ohne diffusiven Verbund mit dem Grundwerkstoff erreicht wird.The invention has for its object to improve a thermal spraying process of the type mentioned with simple means so that at lower heat input into the base material a closed, melted in itself protective layer is achieved without diffusive compound with the base material.

Erfindungsgemäß wird die Aufgabe durch ein Plasmaspritzverfahren gemäß Anspruch 1 gelöst, bei dem als Pulver eine selbstfließende Metalllegierung mir grober Körnung auf die metallischen Wände gespritzt wird, wobei die Schutzschicht nach dem Aufspritzen angeschmolzen wird.According to the invention, the object is achieved by a plasma spraying process according to claim 1, in which a self-flowing metal alloy of coarse grain size is sprayed onto the metallic walls as powder, the protective layer being melted after spraying.

Der Erfindung liegt die Erkenntnis zugrunde, dass die Temperatur des Grundwerkstoffs bei dem Plasmaspritzverfahren grundsätzlich nur gering erhöht wird, da der Plasmastrahl selbst den Grundwerkstoff gar nicht erreicht. Die Erfindung geht aber weiter, indem ein grobkörniges Pulver als Beschichtungswerkstoff bzw. Zusatzwerkstoff in dem erfindungsgemäßen Plasmaspritzverfahren eingesetzt wird, wobei anstelle des thermisch hochbelastenden Einschmelzens lediglich ein Anschmelzen der Schutzschicht bei wesentlich geringeren Temperaturen durchgeführt wird und damit erheblich geringere thermische Belastungen in den Grundwerkstoff eingeleitet werden.The invention is based on the finding that the temperature of the base material in the plasma spraying process is basically only slightly increased, since the plasma jet itself does not even reach the base material. However, the invention proceeds by using a coarse-grained powder as the coating material or filler material in the plasma spraying process according to the invention, wherein instead of the high thermal melting, only a melting of the protective layer is carried out at much lower temperatures and thus significantly lower thermal loads are introduced into the base material ,

In bevorzugter Ausführung weist das Pulver bzw. die selbstfließenden Metalllegierung eine Körnung von 90 bis 180 µm auf, wobei die Schutzschicht nach dem Aufspritzen eine Schichtdicke von 0,2 bis 1 mm vorzugsweise 0,3 bis 0,6 mm hat. Die Porosität der Schutzschicht beträgt vor dem Anschmelzen 0,5 bis 3%.In a preferred embodiment, the powder or the self-flowing metal alloy has a grain size of 90 to 180 .mu.m, wherein the protective layer after spraying has a layer thickness of 0.2 to 1 mm, preferably 0.3 to 0.6 mm. The porosity of the protective layer before melting is 0.5 to 3%.

In günstiger Ausgestaltung wird als Pulver eine selbstfließende Metalllegierung verwendet, welche zumindest folgende Bestandteile hat: 77,35 Gew.-% Ni; 11,5 Gew.-% Cr; 0,65 Gew.-% C; 2,5 Gew.-% B; 3,75 Gew.-% Si; 4,25 Gew.-% Fe.In a favorable embodiment, a self-fluxing metal alloy is used as powder, which has at least the following constituents: 77.35 wt .-% Ni; 11.5% by weight Cr; 0.65% by weight C; 2.5% by weight B; 3.75% by weight of Si; 4.25% by weight of Fe.

Die Schutzschicht weist nach dem Anschmelzen eine Härte von 48 bis 52 HRC auf.The protective layer has a hardness of 48 to 52 HRC after melting.

In bevorzugter Ausführung wird die selbstfließende Metalllegierung mit einem Plasmaspritzverfahren mit zumindest den folgenden Parametern aufgespritzt:

  • Als Gas wird vorzugsweise Argon verwendet
  • Der Gasdruck beträgt vorzugsweise 6,2 bar
  • Die Spannung beträgt vorzugsweise 38 bis 50V
  • Als Trägergas wird bevorzugt Argon verwendet
  • Der Trägergasdruck beträgt vorzugsweise 4,0 bar
  • Die Förderrate beträgt vorzugsweise 1,35kg/h
  • Der Spritzabstand beträgt vorzugsweise 100 bis 150 mm
  • Der Spritzwinkel beträgt vorzugsweise 90°
  • Die Werkstückbewegung ist insbesondere bei Rohren rotierend
  • Der Vorschub der Plasmapistole beträgt vorzugsweise 0,5m/min
In a preferred embodiment, the self-fluxing metal alloy is sprayed with a plasma spraying process having at least the following parameters:
  • Argon is preferably used as the gas
  • The gas pressure is preferably 6.2 bar
  • The voltage is preferably 38 to 50V
  • Argon is preferably used as the carrier gas
  • The carrier gas pressure is preferably 4.0 bar
  • The delivery rate is preferably 1.35 kg / h
  • The spray distance is preferably 100 to 150 mm
  • The spray angle is preferably 90 °
  • The movement of the workpiece is rotating, in particular in the case of pipes
  • The advance of the plasma gun is preferably 0.5 m / min

Vor dem Aufspritzen des Pulvers wird das Werkstück, vorzugsweise ein Rohr mit Elektroschmelzkorund oder dergleichen gestrahlt. In zweckmäßiger Ausführung wird das Pulver bzw. die selbstfließende Metalllegierung vor dem Spritzprozess auf ca. 25°C erwärmt.Before spraying the powder, the workpiece, preferably a tube with electrofused corundum or the like, is blasted. In an expedient embodiment, the powder or the self-flowing metal alloy is heated to about 25 ° C. before the injection process.

Das Anschmelzen der Schutzschicht nach dem Aufspritzen wird in zweckmäßiger Ausführung mit einer neutralen Flamme (Acetylen/Sauerstoff) durchgeführt, wobei die Schutzschicht im Vergleich zum Einschmelzen auf eine wesentlich geringere Temperatur von ca. 800°C aufgewärmt wird, wodurch vorteilhaft ein diffusiver Verbund der Schutzschicht zum Grundwerkstoff vermieden ist. Damit sind aber auch Gefügeänderungen des Grundwerkstoffs vermieden, weswegen sich das erfindungsgemäße Plasmaspritzverfahren auch bei kritischen Werkstoffen wie z.B. 15Mo3, 10CrMo910 oder 13CrMo45 anwenden lässt. Die angeschmolzene Schutzschicht kühlt sehr schnell ab, was auch die Bildung einer geschlossenen, harten Hülle (Schutzschicht) positiv beeinflusst. Bevorzugt kann das Werkstück bzw. das beschichtete Rohr an Luft abkühlen.The melting of the protective layer after spraying is carried out expediently with a neutral flame (acetylene / oxygen), wherein the protective layer compared to the melting to a much lower Temperature of about 800 ° C is heated, which advantageously avoids a diffusive composite of the protective layer to the base material. But this also structural changes of the base material are avoided, which is why the plasma spraying process according to the invention can also be applied to critical materials such as 15Mo3, 10CrMo910 or 13CrMo45. The melted protective layer cools down very quickly, which also positively influences the formation of a closed, hard shell (protective layer). Preferably, the workpiece or the coated tube to cool in air.

Das erfindungsgemäße Plasmaspritzverfahren eignet sich insbesondere zur Anwendung an Überhitzerrohren in Müllverbrennungsanlagen, ohne die Anwendung hierauf zu beschränken. Insbesondere in Müllverbrennungsanlagen hat es sich gezeigt, dass reine Spritzschichten als Schutzschichten zwar dem normalen Betrieb gerecht werden; ein erforderlicher Reinigungsprozess (Strahlprozess) führt jedoch häufig zu einer Schädigung, die letztlich den Ausfall der Schutzschicht herbeiführt. Mittels des erfindungsgemäßen Plasmaspritzverfahrens jedoch wird eine kompakte, gasdichte, fest mit dem Grundwerkstoff verbundene Schutzschicht erzeugt, die auch einem Strahlprozess widersteht, da die Diffusionsschicht bzw. eine Gefügeänderung des Grundwerkstoffs vermieden ist.The plasma spraying process according to the invention is particularly suitable for use on superheater pipes in waste incineration plants, without restricting the application thereof. In particular, in waste incineration plants, it has been found that pure sprayed coatings as protective layers, although the normal operation meet; However, a required cleaning process (blasting process) often leads to damage, which ultimately causes the failure of the protective layer. By means of the plasma spraying process according to the invention, however, a compact, gas-tight, firmly bonded to the base material protective layer is generated, which also resists a blasting process, since the diffusion layer or a structural change of the base material is avoided.

Insgesamt beinhaltet das erfindungsgemäße Plasmaspritzverfahren gegenüber den bisher bekannten Verfahren folgende Vorteile:

  • Es wird eine homogene Schichtstruktur erzeugt;
  • Gegenüber konventionellen Spritzschichten wird eine doppelte Schichtdicke erreicht
  • Es wird eine feste, geschlossene und gasdichte Schicht erzeugt;
  • Keine ausgeprägte Diffusionszone, wobei die Rißgefahr vermieden ist;
  • Problemzonen wie Rohrbögen und angeschweißte Halterungen sind riss- und verzugsfrei herzustellen;
  • Der Reinigungsprozess an Überhitzerbündeln mit beschichteten Rohren ist problemlos möglich;
Overall, the plasma spraying method according to the invention has the following advantages over the previously known methods:
  • It creates a homogeneous layer structure;
  • Compared to conventional sprayed coatings, a double layer thickness is achieved
  • A solid, closed and gas-tight layer is produced;
  • No pronounced diffusion zone, whereby the risk of cracking is avoided;
  • Problem areas such as pipe bends and welded brackets must be produced free of cracks and distortion;
  • The cleaning process on superheater bundles with coated pipes is easily possible;

Bei Biege- und Zugversuchen hat es sich gezeigt, dass die erfindungsgemäß hergestellte Beschichtung zieharmonikaartig abplatzt. Schliffbilder zeigten nach dem Auftragen der Schutzschicht und dem anschließenden Anschmelzen, dass keine Werkstofftrennungen bzw. Gefügeänderungen im Grundwerkstoff vorhanden waren.In bending and tensile tests, it has been shown that the coating produced according to the invention peels off like a concertina. Micrographs showed after applying the protective layer and the subsequent melting, that no material separations or microstructural changes in the base material were present.

Claims (9)

  1. Thermal spraying method for producing a protective layer on metallic walls subjected to hot flue gases in a plasma spraying method, in which method a self-flowing metal alloy is applied as powder to the metallic walls, characterized in that the self-flowing metal alloy has a grain size of 90 to 180 µm, wherein the protective layer is only partially melted with a neutral flame after it has been sprayed on, wherein the protective layer is only heated to such a temperature that a diffusive bond between the protective layer and the base material is avoided, wherein the self-flowing metal alloy contains nickel as the main constituent.
  2. Thermal spraying method according to Claim 1, characterized in that the layer thickness of the protective layer after it has been sprayed on is 0.2 to 1 mm.
  3. Thermal spraying method according to Claim 1 or 2, characterized in that the layer thickness of the protective layer after it has been sprayed on is 0.3 to 0.6 mm.
  4. Thermal spraying method according to one of the preceding claims, characterized in that the porosity of the protective layer before it is partially melted is 0.5 to 3%.
  5. Thermal spraying method according to one of the preceding claims, characterized in that the powder used is a self-flowing metal alloy containing at least the following constituents: 77.35% by weight Ni; 11.5% by weight Cr; 0.65% by weight C; 2.5% by weight B; 3.75% by weight Si; 4.25% by weight Fe.
  6. Thermal spraying method according to one of the preceding claims, characterized in that the hardness of the protective layer after it has been partially melted is 48 to 52 HRC.
  7. Thermal spraying method according to one of the preceding claims, characterized in that the powder is heated to a temperature of approximately 25°C before it is sprayed on.
  8. Thermal spraying method according to one of the preceding claims, characterized in that a plasma spraying method is used to spray the protective layer onto metallic walls of boiler tubes which are subjected to hot flue gases.
  9. Use of a powder made of a self-flowing metal alloy having a grain size of 90 to 180 µm for a thermal spraying method for producing a protective layer on metallic walls subjected to hot flue gases, according to one of the preceding claims, wherein the protective layer is only partially melted with a neutral flame after it has been sprayed on in a plasma spraying method, wherein the protective layer is only heated to such a temperature that a diffusive bond between the protective layer and the base material is avoided, wherein the self-flowing metal alloy contains nickel as the main constituent.
EP08004327A 2007-04-27 2008-03-08 Plasma spray method for coating excess heat tubes Active EP1985722B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PL08004327T PL1985722T3 (en) 2007-04-27 2008-03-08 Plasma spray method for coating excess heat tubes

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102007020420A DE102007020420B4 (en) 2007-04-27 2007-04-27 Plasma spraying process for coating superheater pipes and using a metal alloy powder

Publications (3)

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EP1985722A2 EP1985722A2 (en) 2008-10-29
EP1985722A3 EP1985722A3 (en) 2009-04-01
EP1985722B1 true EP1985722B1 (en) 2011-10-26

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EP (1) EP1985722B1 (en)
AT (1) ATE530676T1 (en)
DE (1) DE102007020420B4 (en)
DK (1) DK1985722T3 (en)
ES (1) ES2375172T3 (en)
HR (1) HRP20120043T1 (en)
PL (1) PL1985722T3 (en)

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US3642519A (en) * 1969-03-21 1972-02-15 Us Air Force Method for the development of hard coat seal surfaces
US4192672A (en) * 1978-01-18 1980-03-11 Scm Corporation Spray-and-fuse self-fluxing alloy powders
US4692305A (en) * 1985-11-05 1987-09-08 Perkin-Elmer Corporation Corrosion and wear resistant alloy
EP0223135A1 (en) * 1985-11-05 1987-05-27 The Perkin-Elmer Corporation Corrosion resistant self-fluxing alloys for thermal spraying
DE4220063C1 (en) 1992-06-19 1993-11-18 Thyssen Guss Ag Process for producing a protective layer on metallic walls exposed to hot gases, in particular flue gases
DE19638228A1 (en) * 1996-08-22 1998-02-26 Castolin Sa Method for producing a corrosion-resistant connection of pipes
WO2006099869A1 (en) * 2005-03-21 2006-09-28 Gerstenberg & Agger A/S A resistant hard coating

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EP1985722A2 (en) 2008-10-29
EP1985722A3 (en) 2009-04-01
DK1985722T3 (en) 2012-02-06
ES2375172T3 (en) 2012-02-27
PL1985722T3 (en) 2012-03-30
HRP20120043T1 (en) 2012-02-29
DE102007020420A1 (en) 2008-10-30
ATE530676T1 (en) 2011-11-15
DE102007020420B4 (en) 2011-02-24

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