EP0672197B1 - Process for producing a protective coating on metal walls subject to attack by hot gases, especially flue gases - Google Patents

Process for producing a protective coating on metal walls subject to attack by hot gases, especially flue gases Download PDF

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Publication number
EP0672197B1
EP0672197B1 EP93912953A EP93912953A EP0672197B1 EP 0672197 B1 EP0672197 B1 EP 0672197B1 EP 93912953 A EP93912953 A EP 93912953A EP 93912953 A EP93912953 A EP 93912953A EP 0672197 B1 EP0672197 B1 EP 0672197B1
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Prior art keywords
powder
protective coating
walls
process according
plasma jet
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EP93912953A
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German (de)
French (fr)
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EP0672197A1 (en
Inventor
Bodo Häuser
Wilhelm Heesen
Johannes Hermsen
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HAEUSER & CO. GMBH
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Hauser & Co GmbH
Thyssen Stahl AG
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    • 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
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • 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
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • C23C4/134—Plasma spraying
    • 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
    • B05B7/22—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 electrically, magnetically or electromagnetically, e.g. by arc
    • 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
    • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • 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
    • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof

Definitions

  • the invention relates to a method for producing a protective layer on hot gases, especially flue gases Walls made of metallic base material, preferably from Incinerators or heat exchangers, in which with the help of a Plasma spraying on the previously cleaned, metallic walls to form the protective layer, a powder made of metallic, carbide, oxide ceramic or silicide materials or mixtures of these Materials is applied.
  • Such protective layers should e.g. on cooling walls of waste heat boilers applied to steel converters. These walls are special exposed to high loads. On one side flow approx. 1400 ° - 1800 ° C hot smoke gases loaded with ash and slag particles along, while on the other side saturated steam pressures of approx. 20 - 80 bar rule.
  • the saturated steam-cooled pipe walls are included Internal pressure gradients of up to 2 bar / min.
  • DE 23 55 532 C2 describes a method for powder deposition welding of metals and alloys on a surface prepared by sandblasting, preheated metal pad known, where the metal pad previously is heated to at least 100 to about 650 ° C.
  • Both at Cladding by means of a stick electrode as well as at Powder build-up welding or flame spraying with subsequent melting becomes the base material when the protective layer is applied very strongly heated, which leads to an undesirable structural change.
  • flame spraying in particular, the melting temperature is in Depending on the spray powder used between 980 and 1060 ° C. Due to the high heat input, there is also Warping of the walls to be coated. When installing these walls can then there are problems and additional costs due to the dimensionality come.
  • the protective layer has a thickness of about 8 to 10 mm and with flame spraying from 1 to 2 mm.
  • DE-AS 26 30 507 is also a process for the production of Protective layers on workpieces against hot gas corrosion and / or known mechanical wear, in which by means of plasma spraying Vacuum a made of different alloys Coating powder is applied to the workpiece. With this Vacuum spraying must be done with considerable effort from the outside inaccessible processing chamber creates a vacuum and the Coating can be carried out. With larger, e.g. B. in the waste heat boiler built-in walls this is not possible.
  • the present invention is based on the object propose generic method in which these problems not occur and in particular the distortion of the workpieces and cracking stresses in the base material can be avoided.
  • the composition of the powder is determined as a function of the existing base material and the later operating conditions, in particular the specified temperature ranges.
  • tensile stresses of between 50 and 800 N / mm 2 , preferably between 500 and 800 N / mm 2
  • These stress states are calculated by means of the thermal expansion coefficients of the base material on the one hand and of test workpieces made of different powders on the other hand. The mathematical determination can then be checked in accordance with DIN 50121.
  • heat exchangers especially of waste heat boilers on steel converters
  • Protective layer that is insensitive to thermal shock and easy to repair against hot gas corrosion and / or mechanical wear become.
  • a final layer thickness of 0.1 to 0.5 mm, preferably 0.15 to 0.25 mm is already sufficient to also have a a significantly longer period than previously possible To prevent wear.
  • a protective layer mainly has an 80 KW plasma spray system Inner powder feed proved to be particularly suitable. It will be there Powder with a grain size of less than 75 microns, preferably 20 to 40 ⁇ m used. This powder can be used to make a very thin powder Layer to be applied, which is the condition of insensitivity to thermal shock and meets the resistance to hot gas corrosion, and high residual stress due to the process-related laminar Layer structure, avoids. The entire layer is conveniently in made at least two transitions.
  • the surface of the walls to be treated can be sprayed before plasma spraying with high-grade corundum, preferably with high-purity white high-grade corundum roughened and activated.
  • the inventive Traverse the surface through the plasma jet and the surface inside melted powder particles only to approx. 40 ° C maximum 60 ° C is heated. This can result in warping of the wall surfaces be excluded.
  • a powder containing a Ni alloy is expediently used.
  • the exposure temperature can be covered with a protective layer treated walls in the range between 300 and 1800 ° C, preferably 600 and 1000 ° C.
  • the voltage behavior in the transition zone of the base material and the applied protective layer in the temperature range between 0 and approximately 1200 ° C. is shown as an example in a voltage-temperature diagram.
  • the basis is the measured, average linear thermal expansion coefficient of the two material partners.
  • tensile stresses above 600 N / mm 2 are present in the transition zone between the base material and the coating material.
  • the Spray layer suddenly due to high temperatures from the converter highly sprayed molten steel and the hot slag.
  • the process is due to the voltage curve represented by the neutral voltage range at approx. 700 ° C is passed and is above 700 ° C in the transition zone Build up compressive stresses that cause the layer to flake off or Prevent cracking in the layer.
  • the usual water-cooled pipes of the waste heat boiler walls are built according to the Stress slowly returns to the tensile state, i.e. in the diagram shows the line of the voltage curve in Drive in the opposite direction.
  • the So-called 0 state instead of 700 ° C also at 400 ° or at 800 ° C lie.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electromagnetism (AREA)
  • Coating By Spraying Or Casting (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
  • Chemical Vapour Deposition (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Laminated Bodies (AREA)

Abstract

A process for producing a protective coating on walls subject to attack by hot gases in a predetermined temperature range, which are made of metal and a predetermined basic material, in combustion plants, heat exchangers or similar installations, in which a powder of metallic, carbide, oxycarbide or silicide materials or mixtures thereof are applied to the metal walls using the plasma jet process. The invention proposes that: a) the surface of the wall is roughened; b) the basic material of the wall is activated; and c) immediately afterwards the powder is applied at room temperature and in atmospheric conditions by the plasma jet process; being d) the composition of the powder selected beforehand so that the stress as a function of the temperature in the unstressed state (at room temperature) found with the aid of the coefficients of heat expansion of the basic material and test-pieces for the transition region between the basic material and the applied coating produced from various powders gives tensile stresses of between 50 and 800 N/mm2 and preferably between 500 and 800 N/mm2, which is reduced to 0 or exhibits slight compression stresses in the predetermined temperature range.

Description

Die Erfindung bezieht sich auf ein Verfahren zur Herstellung einer Schutzschicht auf mit heißen Gasen, insbesondere Rauchgasen beaufschlagten Wänden aus metallischem Grundwerkstoff, vorzugsweise von Verbrennungsanlagen oder Wärmetauschern, bei dem mit Hilfe eines Plasmaspritzverfahrens auf die zuvor gereinigten, metallischen Wände zur Bildung der Schutzschicht ein Pulver aus metallischen, karbidischen, oxidkeramischen oder silicidischen Werkstoffen oder Mischungen dieser Werkstoffe aufgetragen wird.The invention relates to a method for producing a protective layer on hot gases, especially flue gases Walls made of metallic base material, preferably from Incinerators or heat exchangers, in which with the help of a Plasma spraying on the previously cleaned, metallic walls to form the protective layer, a powder made of metallic, carbide, oxide ceramic or silicide materials or mixtures of these Materials is applied.

Derartige Schutzschichten sollen z.B. auf Kühlwände von Abhitzekesseln an Stahlkonvertern aufgetragen werden. Diese Wände sind besonders hohen Belastungen ausgesetzt. Auf der einen Seite strömen ca. 1400° - 1800° C heiße, mit Asche und Schlackepartikeln beladene Rauchgase entlang, während auf der anderen Seite Sattdampfdrücke von ca. 20 - 80 bar herrschen. Die sattdampfgekühlten Rohrwände haben dabei lnnendruck-Gradienten von bis zu 2 bar/min.Such protective layers should e.g. on cooling walls of waste heat boilers applied to steel converters. These walls are special exposed to high loads. On one side flow approx. 1400 ° - 1800 ° C hot smoke gases loaded with ash and slag particles along, while on the other side saturated steam pressures of approx. 20 - 80 bar rule. The saturated steam-cooled pipe walls are included Internal pressure gradients of up to 2 bar / min.

Aus der DE 23 55 532 C2 ist ein Verfahren zum Pulverauftragsschweißen von Metallen und Legierungen auf eine durch Sandstrahlen vorbereitete, vorgewärmte Metallunterlage bekannt, bei dem die Metallunterlage zuvor auf mindestens 100 bis etwa 650° C erhitzt wird. Sowohl beim Auftragsschweißen mittels Stabelektrode als auch beim Pulverauftragsschweißen oder Flammspritzen mit nachträglichem Einschmelzen wird beim Aufbringen der Schutzschicht der Grundwerkstoff sehr stark erhitzt, was zu einer unerwünschten Gefügeänderung führt. Insbesondere bei dem Flammspritzen liegt die Einschmelztemperatur in Abhängigkeit von dem verwendeten Spritzpulver zwischen 980 und 1060° C. Bedingt durch die hohe Wärmeeinbringung kommt es außerdem zum Verzug der zu beschichtenden Wände. Beim Einbau dieser Wände kann es dann zu Problemen und zusätzlichen Kosten wegen der Maßungenadigkeiten kommen. Wenn die Schutzschichten mit diesen bekannten Verfahren nachträglich aufgebracht werden, können die temperaturbedingten Spannungen nicht in Form von Verzug reagieren, sondern führen bei den eingebauten Wandelementen zu Rissen in der Oberfläche, insbesondere im Bereich der Schweißnähte. Beim Auftragsschweißen hat die Schutzschicht eine Dicke von etwa 8 bis 10 mm und beim Flammspritzen von 1 bis 2 mm.DE 23 55 532 C2 describes a method for powder deposition welding of metals and alloys on a surface prepared by sandblasting, preheated metal pad known, where the metal pad previously is heated to at least 100 to about 650 ° C. Both at Cladding by means of a stick electrode as well as at Powder build-up welding or flame spraying with subsequent melting becomes the base material when the protective layer is applied very strongly heated, which leads to an undesirable structural change. In the case of flame spraying in particular, the melting temperature is in Depending on the spray powder used between 980 and 1060 ° C. Due to the high heat input, there is also Warping of the walls to be coated. When installing these walls can then there are problems and additional costs due to the dimensionality come. If the protective layers with these known Processes can be applied subsequently, the do not react to temperature-related tensions in the form of warpage, but lead to cracks in the built-in wall elements Surface, especially in the area of the weld seams. At the The protective layer has a thickness of about 8 to 10 mm and with flame spraying from 1 to 2 mm.

Aus der DE-AS 26 30 507 ist außerdem ein Verfahren zur Herstellung von Schutzschichten auf Werkstücken gegen Heißgaskorrosion und/oder mechanischen Verschleiß bekannt, bei dem mittels Plasmaspritzen im Vakuum ein aus verschiedenen Legierungen bestehendes Beschichtungspulver auf das Werkstück aufgetragen wird. Bei diesem Vakuumspritzverfahren muß mit erheblichem Aufwand in einer von außen nicht zugänglichen Bearbeitungskammer ein Vakuum erzeugt und die Beschichtung durchgeführt werden. Bei größeren, z. B. im Abhitzekessel eingebauten Wänden ist dies nicht möglich.DE-AS 26 30 507 is also a process for the production of Protective layers on workpieces against hot gas corrosion and / or known mechanical wear, in which by means of plasma spraying Vacuum a made of different alloys Coating powder is applied to the workpiece. With this Vacuum spraying must be done with considerable effort from the outside inaccessible processing chamber creates a vacuum and the Coating can be carried out. With larger, e.g. B. in the waste heat boiler built-in walls this is not possible.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein gattungsgemäßes Verfahren vorzuschlagen, bei dem diese Probleme nicht auftreten und insbesondere der Verzug der Werkstücke und rißbildende Spannungen im Grundwerkstoff vermieden werden.The present invention is based on the object propose generic method in which these problems not occur and in particular the distortion of the workpieces and cracking stresses in the base material can be avoided.

Die erfindungsgemäße Lösung der Aufgabe ist im Kennzeichen des Anspruchs 1 wiedergegeben. Die Unteransprüche 2 bis 8 enthalten sinnvolle ergänzende Verfahrensschritte.The achievement of the object is in the character of Claim 1 reproduced. Subclaims 2 to 8 contain sensible additional procedural steps.

Bei dem erfindungsgemäßen Verfahren wird vor dem Auftragen des Pulvers mit dem atmosphärischen Plasmaspritzverfahren nicht nur die Oberfläche der Wände aufgerauht, sondern auch der Grundwerkstoff der Wände in der Weise mit hochreinem Edelkorund aktiviert, daß Störungen im metallischen Gitter erzeugt werden, wodurch die Adhäsionskräfte erhöht werden. Unmittelbar anschließend, bevor diese Störungen im Gitter wieder aufgehoben sind, wird dann unter atmosphärischen wird dann unter atmosphärischen Bedingungen nach dem Plasmaspritzverfahren das Pulver auf die Wände aufgetragen, deren Oberfläche dabei etwa Raumtemperatur behält.In the method according to the invention, before the Powder with the atmospheric plasma spray process not only that Surface of the walls roughened, but also the base material of the Walls in such a way activated with high purity corundum that faults generated in the metallic grid, reducing the adhesive forces increase. Immediately afterwards, before these faults in the Grids are lifted again, then becomes atmospheric is then under atmospheric conditions after the plasma spraying process the powder applied to the walls, the surface of which maintains about room temperature.

Die Zusammensetzung des Pulvers wird in Abhängigkeit von dem vorhandenen Grundwerkstoff und den späteren Betriebsbedingungen, insbesondere den vorgegebenen Temperaturbereichen, bestimmt. Erfindungsgemäß sollen für den Übergangsbereich zwischen Grundwerkstoff und aufgetragener Schicht im nichtbeanspruchten Zustand, d.h. bei Raumtemperatur, Zugspannungen zwischen 50 und 800 N/mm2, vorzugsweise zwischen 500 und 800 N/mm2 vorliegen, die in dem vorgegebenen beanspruchten Temperaturbereich im wesentlichen auf 0 abgebaut sind oder geringe Druckspannungen aufweisen. Diese Spannungszustände (vgl. beigefügte Figur) werden rechnerisch mit Hilfe der Wärmeausdehnungskoeffizienten von Grundwerkstoff einerseits und von aus verschiedenen Pulvern hergestellten Probewerkstücken andererseits ermittelt. Eine Überprüfung der rechnerischen Bestimmung kann dann nach DIN 50121 durchgeführt werden.The composition of the powder is determined as a function of the existing base material and the later operating conditions, in particular the specified temperature ranges. According to the invention, tensile stresses of between 50 and 800 N / mm 2 , preferably between 500 and 800 N / mm 2, should be present for the transition area between the base material and the applied layer in the non-stressed state, ie at room temperature, which are substantially reduced to 0 in the specified claimed temperature range are or have low compressive stresses. These stress states (cf. attached figure) are calculated by means of the thermal expansion coefficients of the base material on the one hand and of test workpieces made of different powders on the other hand. The mathematical determination can then be checked in accordance with DIN 50121.

Mit dem erfindungsgemäßen Verfahren kann z.B. auf ebenen oder gebogenen Wänden von Verbrennungsanlagen, Wärmetauschern, insbesondere von Abhitzekesseln an Stahlkonvertern eine wärmeschockunempfindliche und reparaturfreundliche Schutzschicht gegen Heißgaskorrosion und/oder mechanischen Verschleiß erzeugt werden.With the method according to the invention e.g. on level or curved walls of incinerators, heat exchangers, especially of waste heat boilers on steel converters Protective layer that is insensitive to thermal shock and easy to repair against hot gas corrosion and / or mechanical wear become.

Es hat sich gezeigt, daß eine Endschichtdicke von 0,1 bis 0,5 mm, vorzugsweise 0,15 bis 0,25 mm bereits ausreicht, um auch über einen wesentlich längeren Zeitraum als bisher möglich einen nennenswerten Verschleiß zu verhindern. Zur Aufbringung einer derartigen Schutzschicht hat sich vor allem eine 80 KW-Plasmaspritzanlage mit Innenpulverzuführung als besonders geeignet erwiesen. Es wird dabei Pulver mit einer Korngröße von weniger als 75 µm, vorzugsweise 20 bis 40 µm verwendet. Mit diesem Pulver kann insbesondere eine sehr dünne Schicht aufgebracht werden, die die Bedingung der Wärmeschockunempfindlichkeit und der Beständigkeit gegen Heißgaskorrosion erfüllt, und hohe Eigenspannung, bedingt durch den prozeßbedingten laminaren Schichtaufbau, vermeidet. Die Gesamtschicht wird günstigerweise in mindestens zwei Übergängen hergestellt.It has been shown that a final layer thickness of 0.1 to 0.5 mm, preferably 0.15 to 0.25 mm is already sufficient to also have a a significantly longer period than previously possible To prevent wear. To apply such a protective layer mainly has an 80 KW plasma spray system Inner powder feed proved to be particularly suitable. It will be there Powder with a grain size of less than 75 microns, preferably 20 to 40 µm used. This powder can be used to make a very thin powder Layer to be applied, which is the condition of insensitivity to thermal shock and meets the resistance to hot gas corrosion, and high residual stress due to the process-related laminar Layer structure, avoids. The entire layer is conveniently in made at least two transitions.

Vor dem Plasmaspritzen kann die zu behandelnde Oberfläche der Wände mit Edelkorund, vorzugsweise mit hochreinem weißen Edelkorund aufgerauht und aktiviert werden.The surface of the walls to be treated can be sprayed before plasma spraying with high-grade corundum, preferably with high-purity white high-grade corundum roughened and activated.

Weiterhin hat es sich als günstig erwiesen, daß beim erfindungsgemäßen Verfahren die Oberfläche durch den Plasmastrahl und die darin aufgeschmolzenen Pulverpartikel nur auf ca. 40° C maximal 60° C erwärmt wird. Hierdurch kann insbesondere ein Verzug der Wandflächen ausgeschlossen werden.Furthermore, it has proven to be advantageous that the inventive Traverse the surface through the plasma jet and the surface inside melted powder particles only to approx. 40 ° C maximum 60 ° C is heated. This can result in warping of the wall surfaces be excluded.

Zweckmäßig wird ein eine Ni-Legierung enthaltendes Pulver verwendet.A powder containing a Ni alloy is expediently used.

Es hat sich gezeigt, daß die atmosphärische Plasmabeschichtung spätestens 45 Min., vorzugsweise spätestens 30 Min. nach der Aktivierung der Oberfläche der Wände durchgeführt werden sollte.It has been shown that atmospheric plasma coating at the latest 45 minutes, preferably at the latest 30 minutes after the Activation of the surface of the walls should be done.

Schließlich kann die Beanspruchungstemperatur der mit einer Schutzschicht behandelten Wände im Bereich zwischen 300 und 1800° C, vorzugsweise 600 und 1000° C liegen.Finally, the exposure temperature can be covered with a protective layer treated walls in the range between 300 and 1800 ° C, preferably 600 and 1000 ° C.

In der beigefügten Figur wird in einem Spannungs-Temperaturdiagramm beispielhaft das Spannungsverhalten in der Übergangszone des Grundwerkstoffes und der aufgebrachten Schutzschicht im Temperaturbereich zwischen 0 und etwa 1200° C dargestellt. Grundlage sind dabei die gemessenen, mittleren linearen Wärmeausdehnungskoeffizienten der beiden Werkstoffpartner.
Im nichtbeanspruchten Zustand der beschichteten Wandfläche eines Konverter-Abhitzekessels sind in der Übergangszone zwischen dem Grundwerkstoff und dem Beschichtungswerkstoff Zugspannungen oberhalb 600 N/mm2 vorhanden. In the attached figure, the voltage behavior in the transition zone of the base material and the applied protective layer in the temperature range between 0 and approximately 1200 ° C. is shown as an example in a voltage-temperature diagram. The basis is the measured, average linear thermal expansion coefficient of the two material partners.
In the non-stressed state of the coated wall surface of a converter waste heat boiler, tensile stresses above 600 N / mm 2 are present in the transition zone between the base material and the coating material.

Im Betriebszustand der beschichteten Abhitzekessel-Wandfläche wird die Spritzschicht plötzlich durch hohe Temperaturen der aus dem Konverter hochspritzenden Stahlschmelze und der heißen Schlacke beaufschlagt. In dem Diagramm ist der Vorgang durch den Spannungsverlauf dargestellt, indem bei ca. 700° C der neutrale Spannungsbereich durchlaufen wird und sich oberhalb 700° C in der Übergangszone Druckspannungen aufbauen, die ein Abplatzen der Schicht oder die Rißbildung in der Schicht verhindern. Durch die üblicherweise wassergekühlten Rohre der Abhitzekesselwände baut sich nach der Beanspruchung langsam der Zugspannungszustand wieder auf, d.h. in dem Diagramm wird die eingezeichnete Linie des Spannungsverlaufes in umgekehrter Richtung durchfahren. In der Figur ist lediglich ein beispielhafter Spannungsverlauf abhängig von der Temperatur dargestellt. Für andere Beanspruchungsbereiche kann naturgemäß auch der sogenannte 0-Zustand statt bei 700° C auch bei 400° oder bei 800° C liegen.In the operating state of the coated waste heat boiler wall surface, the Spray layer suddenly due to high temperatures from the converter highly sprayed molten steel and the hot slag. In the diagram, the process is due to the voltage curve represented by the neutral voltage range at approx. 700 ° C is passed and is above 700 ° C in the transition zone Build up compressive stresses that cause the layer to flake off or Prevent cracking in the layer. By the usual water-cooled pipes of the waste heat boiler walls are built according to the Stress slowly returns to the tensile state, i.e. in the diagram shows the line of the voltage curve in Drive in the opposite direction. In the figure is only an example Voltage curve shown depending on the temperature. For other areas of use, the So-called 0 state instead of 700 ° C also at 400 ° or at 800 ° C lie.

Claims (8)

  1. Process for producing a protective coating on walls made of metallic base material exposed to hot gases, especially flue gases, preferably in combustion plants or heat exchangers, in which a powder of metallic, carbide, oxide ceramic or silicide materials, or any mixtures thereof, is applied onto the previously cleaned metallic walls by means of a plasma jet technique to form the said protective coating, characterized in that
    a) the surface of the walls is roughened and activated with high-purity special fused alumina and
    b) immediately afterwards, the powder is applied by the plasma jet technique at ambient temperature and under atmospheric conditions,
    c) the composition of the powder having previously been selected so that the stress as a function of the temperature in the unstressed state (at room temperature) determined, by means of the thermal expansion coefficients of the base material and test pieces made of various powders, for the transition zone between base material and coating applied gives tensile stresses of between 50 and 800 N/mm2, preferably between 500 and 800 N/mm2, which is reduced to zero or exhibits slight compressive stresses in the specified temperature range of 300 to 1,800 °C, preferably of 600 to 1,000 °C.
  2. Process according to claim 1, characterized in that the protective coating applied has a final thickness of 0.1 to 0.5 mm, preferably 0.15 to 0.25 mm.
  3. Process according to claim 1 or 2, characterized in that the protective coating is applied by an 80 KW plasma jet installation with internal powder feeding.
  4. Process according to at least one of the claims 1 through 3, characterized in that powder having a grain size of less than 75 µm, preferably 20 to 40 µm, is used for applying the protective coating.
  5. Process according to at least one of the claims 1 through 4, characterized in that the protective coating is applied in at least two passes.
  6. Process according to at least one of the preceding claims, characterized in that the surface of the walls is only heated to approx. 45 °C, maximum 60 °C, by the plasma jet and the powder particles melted in the same.
  7. Process according to at least one of the preceding claims, characterized in that a nickel alloy containing powder is used to produce the protective coating.
  8. Process according to claim 1, characterized in that atmospheric plasma spraying is carried out not later than 45 minutes, preferably not later than 30 minutes, after activation of the wall surface.
EP93912953A 1992-06-19 1993-06-11 Process for producing a protective coating on metal walls subject to attack by hot gases, especially flue gases Expired - Lifetime EP0672197B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4220063 1992-06-19
DE4220063A DE4220063C1 (en) 1992-06-19 1992-06-19 Process for producing a protective layer on metallic walls exposed to hot gases, in particular flue gases
PCT/EP1993/001483 WO1994000616A1 (en) 1992-06-19 1993-06-11 Process for producing a protective coating on metal walls subject to attack by hot gases, especially flue gases

Publications (2)

Publication Number Publication Date
EP0672197A1 EP0672197A1 (en) 1995-09-20
EP0672197B1 true EP0672197B1 (en) 1999-03-31

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EP (1) EP0672197B1 (en)
JP (1) JP3150697B2 (en)
KR (1) KR950701983A (en)
AT (1) ATE178364T1 (en)
AU (1) AU672009B2 (en)
BR (1) BR9306566A (en)
CA (1) CA2138255A1 (en)
CZ (1) CZ313794A3 (en)
DE (2) DE4220063C1 (en)
ES (1) ES2132237T3 (en)
PL (1) PL171965B1 (en)
RU (1) RU2107744C1 (en)
SK (1) SK156394A3 (en)
WO (1) WO1994000616A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT411625B (en) * 2000-04-28 2004-03-25 Vaillant Gmbh Heat exchanger, especially a coiled tube heat exchanger of a water heater, is coated using a plasma stream containing added silicon dioxide, aluminum oxide, silicon compound and-or titanium compound

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0727504A3 (en) * 1995-02-14 1996-10-23 Gen Electric Plasma coating process for improved bonding of coatings on substrates
CZ298780B6 (en) * 2003-12-23 2008-01-23 Koexpro Ostrava, A. S. Protective coating of tools and implements for preventing formation of mechanical incentive sparks
DE102007020420B4 (en) 2007-04-27 2011-02-24 Häuser & Co. GmbH Plasma spraying process for coating superheater pipes and using a metal alloy powder
DE102013010126B4 (en) 2013-06-18 2015-12-31 Häuser & Co. GmbH Plasmapulverspritzverfahren and apparatus for coating panels for boiler walls in conjunction with a laser beam device
CN108101062A (en) * 2018-01-17 2018-06-01 江苏中能硅业科技发展有限公司 A kind of preparation process of polycrystalline silicon reducing furnace and its furnace tube inner wall functional layer
JP7370794B2 (en) 2019-09-30 2023-10-30 セコム株式会社 security equipment
JP7370793B2 (en) 2019-09-30 2023-10-30 セコム株式会社 security equipment

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DE2630507A1 (en) * 1976-07-07 1978-01-12 Motoren Turbinen Union PROCESS FOR THE PRODUCTION OF PROTECTIVE LAYERS ON WORKPIECES

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US4588607A (en) * 1984-11-28 1986-05-13 United Technologies Corporation Method of applying continuously graded metallic-ceramic layer on metallic substrates
JP2695835B2 (en) * 1988-05-06 1998-01-14 株式会社日立製作所 Ceramic coated heat resistant material
DE3815436A1 (en) * 1988-05-06 1989-11-16 Muiden Chemie B V DRIVE CHARGES FOR LARGE-CALIBRED BULLETS
DE3821658A1 (en) * 1988-06-27 1989-12-28 Thyssen Guss Ag Process for producing corrosion-resistant and wear-resistant layers on printing press cylinders
CA2053928A1 (en) * 1990-10-24 1992-04-25 Toshihiko Hashimoto Benzopyran derivatives having anti-hypertensive and vasodilartory activity, their preparation and their therapeutic use

Patent Citations (1)

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DE2630507A1 (en) * 1976-07-07 1978-01-12 Motoren Turbinen Union PROCESS FOR THE PRODUCTION OF PROTECTIVE LAYERS ON WORKPIECES

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT411625B (en) * 2000-04-28 2004-03-25 Vaillant Gmbh Heat exchanger, especially a coiled tube heat exchanger of a water heater, is coated using a plasma stream containing added silicon dioxide, aluminum oxide, silicon compound and-or titanium compound

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PL171965B1 (en) 1997-07-31
KR950701983A (en) 1995-05-17
WO1994000616A1 (en) 1994-01-06
CZ313794A3 (en) 1995-08-16
ES2132237T3 (en) 1999-08-16
ATE178364T1 (en) 1999-04-15
AU4325093A (en) 1994-01-24
BR9306566A (en) 1999-01-12
AU672009B2 (en) 1996-09-19
DE59309491D1 (en) 1999-05-06
DE4220063C1 (en) 1993-11-18
EP0672197A1 (en) 1995-09-20
JP3150697B2 (en) 2001-03-26
JPH08501350A (en) 1996-02-13
RU2107744C1 (en) 1998-03-27
CA2138255A1 (en) 1994-01-06
RU94046201A (en) 1996-10-20
SK156394A3 (en) 1997-02-05

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