EP0798402B1 - Layer for protection against oxydation - Google Patents

Layer for protection against oxydation Download PDF

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Publication number
EP0798402B1
EP0798402B1 EP97200888A EP97200888A EP0798402B1 EP 0798402 B1 EP0798402 B1 EP 0798402B1 EP 97200888 A EP97200888 A EP 97200888A EP 97200888 A EP97200888 A EP 97200888A EP 0798402 B1 EP0798402 B1 EP 0798402B1
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EP
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Prior art keywords
layer
oxidation protection
oxidation
carbon
protection layer
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EP97200888A
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German (de)
French (fr)
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EP0798402A1 (en
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Hans-Peter Dr. Martinz
Manfred Sulik
Joachim Dr. Ing. Disam
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Plansee SE
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Plansee SE
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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
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • Y10T428/12576—Boride, carbide or nitride component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • Y10T428/12597—Noncrystalline silica or noncrystalline plural-oxide component [e.g., glass, etc.]
    • Y10T428/12604—Film [e.g., glaze, etc.]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • Y10T428/12625—Free carbon containing component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
    • Y10T428/12819—Group VB metal-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
    • Y10T428/12826—Group VIB metal-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
    • Y10T428/12826—Group VIB metal-base component
    • Y10T428/1284—W-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/31504—Composite [nonstructural laminate]
    • Y10T428/31678—Of metal

Definitions

  • the invention relates to a high-melting on a substrate Metal from the group of molybdenum, tungsten, tantalum, niobium and their alloys, or composite materials thereof, applied anti-oxidation layer, which in consists essentially of silicon and 1-14% by weight boron.
  • Refractory metals have the properties, up to the highest Temperatures to maintain their strength. However, the problem is that this Metals and alloys have little resistance to Have oxidation if they are air or at high temperatures above 400 ° C are exposed to other oxidizing media.
  • the surface of the high-melting metals In order to improve this strong susceptibility to oxidation, it is known to provide the surface of the high-melting metals with appropriate protective layers.
  • the application of coatings based on silicon, which form a corresponding silicide through a diffusion annealing treatment with the high-melting metal have been widely used for this purpose. If such coated high-melting metals are exposed to an oxygen-containing atmosphere at high temperatures, an oxide layer forms on the surface of the silicide, which acts as a protective layer against further oxidation. If a pure silicon layer is applied to the high-melting metal, the oxide layer on the silicide layer is SiO 2 .
  • SiO 2 forms relatively slowly and has a high melting point, so that such a layer has poor crack-healing properties, in particular at operating temperatures of the high-melting metal below 1200 ° C., and thus forms in many cases inadequate protection against oxidation.
  • modified coatings has become particularly important Two-substance basis, such as SiC, SiB, SiGe, SiMn, SiTi, SiCr, but also on a three-substance basis, such as SiCrAl, SiTiAl, SiCrB, SiCrTi and SiCrFe, enforced in practice.
  • Two-substance basis such as SiC, SiB, SiGe, SiMn, SiTi, SiCr
  • three-substance basis such as SiCrAl, SiTiAl, SiCrB, SiCrTi and SiCrFe
  • modified coatings based on silicon has the advantage that, compared to pure SiO 2, lower melting oxide mixtures form on the silicide layers, so that such coating layers have good crack-healing properties and protect the surface of the high-melting metal over a wide temperature range.
  • the oxidation protection layers can be applied by a wide variety of coating processes, such as plasma spraying, electrophoresis, melt flow electrolysis, melt immersion processes, CVD or PVD processes, by applying a slip of the desired powder mixture to the surface of the refractory metal (slurry coating) or by outsourcing the refractory metal in a corresponding powder mixture with activator (pack cementation).
  • a diffusion treatment is carried out at temperatures between 1200 ° C and 1600 ° C under protective gas or in a high vacuum to form the silicide layers.
  • the high-temperature coating processes (melt flow electrolysis, hot-dip process, CVD process, pack cementation and generally also plasma spraying)
  • sufficiently dense layers are deposited so that the silicide layers can form during the oxidation without oxygen being able to penetrate to a greater extent .
  • U.S. Patent No. 5,246,736 describes a method according to which a Refractory composite material in or on the surface of which Corrosion protection using a ternary "silicon-boron-carbon system" uniform distribution of elements is applied or applied.
  • the Boron concentration in this Si-B-C system should not be less than 5 atomic% be.
  • the refractory composite material consists of fibrous reinforcing elements, which are embedded and compressed in a matrix, whereby loud Description of the fibers generally made of carbon or ceramic, such as Silicon carbide.
  • the matrix consists of carbon or at least partly made of SiC.
  • the object of the present invention is therefore an oxidation protection layer for high-melting metals to create an improved layer adhesion, Uniformity and tightness and thus a significantly improved Protection against oxidation compared to previously known oxidation protection layers having.
  • the oxidation protection layer contains 0.1 - 4% by weight of carbon in addition to boron and silicon.
  • An oxidation protection layer consisting of 5 to 12% by weight boron, 0.5 to 3% by weight carbon, balance silicon.
  • the oxidation protection layer according to the invention has proven itself extremely well both for massive substrates made of high-melting metals and for intermediate layers made of these materials. It was completely surprising and to this extent not to be expected that such small amounts of carbon in the oxidation protection layer could result in improvements in the oxidation resistance, which can go up to a factor of 2 compared to pure boron silicon layers for certain conditions of use.
  • the carbon added to produce the protective layer obviously serves not only as an alloying element, but also as an activator that removes diffusion-inhibiting oxygen in the form of CO or CO 2 during high-temperature coating, during heat treatment or even in the first period of use in an oxidizing atmosphere , which could be recognized from the fact that the carbon content in the heat-treated or in the oxidation protection layer that was already in use for a short time at elevated temperature is up to a factor of 10 less than the originally applied amount of carbon. This initially reduced carbon content then stabilizes and remains largely constant until the oxidation protection layer fails.
  • the special oxidation-improving effect of the carbon was in no way foreseeable, since the carbonization of the substrate material was primarily to be expected for the person skilled in the art.
  • the layer thicknesses of the oxidation protection layer according to the invention which are of interest in practice lie in a range between 50 ⁇ m and 500 ⁇ m. In a particularly preferred embodiment of the oxidation protection layer, layer thicknesses between 100 and 300 ⁇ m have proven successful.
  • oxidation protection layers according to the invention is in principle possible with all known coating processes.
  • atmospheric plasma spraying and the slip process have proven to be particularly advantageous coating processes.
  • Cylindrical test specimens with a diameter of 10 - 25 mm and a length of 50 - 250 mm made of molybdenum were sandblasted on the surface and all sharp edges were rounded.
  • a powder mixture of 880 g silicon powder, 100 g boron powder and 20 g carbon powder was mixed in a tumble mixer for 30 minutes.
  • a corresponding slip was then prepared by adding 560 ml of a colorless nitro lacquer, dissolved in 140 ml of nitro thinner, and homogenizing the mixture in a tumble mixer for four hours.
  • the test specimens were coated with slurry by spraying. After air drying for 24 hours, the test specimens were subjected to protective gas annealing (H 2 , 1 bar) at 1370 ° C.
  • test specimens were then freed from poorly adhering slip residues and optically checked for layer defects such as cracks or flaking and, if necessary, coated again.
  • the specimens coated in this way had layer thicknesses in the range between 50 and 100 ⁇ m.
  • the coated test specimens were annealed in air at 1200 ° C., whereby an average service life of 3000 hours until the oxidation protection layer failed.
  • test specimens were coated in the same way with a slip of the same composition, but without carbon components, and also tested in air at 1200 ° C. With the specimens coated in this way, an average service life of only about 2000 hours could be determined.
  • Example 2 Plate-like samples, as in Example 2, but made of tungsten, were also used the same wettable powder and the same conditions as in Example 2 coated. When the samples coated in this way glow at 1400 ° C Air reached an average life of 200 hours.

Description

Die Erfindung betrifft eine auf einem Substrat aus einem hochschmelzenden Metall aus der Gruppe Molybdän, Wolfram, Tantal, Niob und deren Legierungen, bzw. Verbundwerkstoffen davon, aufgebrachte Oxidationsschutzschicht, die im wesentlichen aus Silizium sowie 1 - 14 Gew.% Bor besteht.The invention relates to a high-melting on a substrate Metal from the group of molybdenum, tungsten, tantalum, niobium and their alloys, or composite materials thereof, applied anti-oxidation layer, which in consists essentially of silicon and 1-14% by weight boron.

Hochschmelzende Metalle besitzen die Eigenschaften, bis zu höchsten Temperaturen ihre Festigkeit beizubehalten. Problematisch ist jedoch, daß diese Metalle und Legierungen eine nur geringe Widerstandsfähigkeit gegenüber Oxidation aufweisen, wenn sie bei hohen Temperaturen von über 400°C Luft oder anderen oxidierenden Medien ausgesetzt sind.Refractory metals have the properties, up to the highest Temperatures to maintain their strength. However, the problem is that this Metals and alloys have little resistance to Have oxidation if they are air or at high temperatures above 400 ° C are exposed to other oxidizing media.

Um diese starke Oxidationsanfälligkeit zu verbesseren ist es bekannt, die Oberfläche der hochschmelzenden Metalle mit entsprechenden Schutzschichten zu versehen. Insbesondere die Aufbringung von Beschichtungen auf Siliziumbasis, die durch eine Diffusionsglühbehandlung mit dem hochschmelzenden Metall ein entsprechendes Silizid bilden, sind für diesen Zweck vielfach zur Anwendung gekommen. Werden derartig beschichtete hochschmelzende Metalle bei hohen Temperaturen sauerstoffhaltiger Atmosphäre ausgesetzt, bildet sich auf der Oberfläche des Silizids eine Oxidschicht, die als Schutzschicht gegen weitere Oxidation wirkt. Wird auf das hochschmelzende Metall eine reine Siliziumschicht aufgebracht, ist die Oxidschicht auf der Silizidschicht SiO2. Reines SiO2 bildet sich jedoch relativ langsam und weist einen hohen Schmelzpunkt auf, sodaß eine derartige Schicht insbesondere bei Einsatztemperaturen des hochschmelzenden Metalles unter 1200°C schlechte Rißheileigenschaften aufweist und damit einen vielfach unzureichenden Oxidationsschutz bildet.In order to improve this strong susceptibility to oxidation, it is known to provide the surface of the high-melting metals with appropriate protective layers. In particular, the application of coatings based on silicon, which form a corresponding silicide through a diffusion annealing treatment with the high-melting metal, have been widely used for this purpose. If such coated high-melting metals are exposed to an oxygen-containing atmosphere at high temperatures, an oxide layer forms on the surface of the silicide, which acts as a protective layer against further oxidation. If a pure silicon layer is applied to the high-melting metal, the oxide layer on the silicide layer is SiO 2 . Pure SiO 2 , however, forms relatively slowly and has a high melting point, so that such a layer has poor crack-healing properties, in particular at operating temperatures of the high-melting metal below 1200 ° C., and thus forms in many cases inadequate protection against oxidation.

Deshalb hat sich die Verwendung modifizierter Beschichtungen insbesondere auf Zweistoffbasis, wie SiC, SiB, SiGe, SiMn, SiTi, SiCr, aber auch auf Dreistoffbasis, wie SiCrAl, SiTiAl, SiCrB, SiCrTi und SiCrFe, in der Praxis durchgesetzt. Therefore, the use of modified coatings has become particularly important Two-substance basis, such as SiC, SiB, SiGe, SiMn, SiTi, SiCr, but also on a three-substance basis, such as SiCrAl, SiTiAl, SiCrB, SiCrTi and SiCrFe, enforced in practice.

Die Verwendung modifizierter Beschichtungen auf Siliziumbasis hat den Vorteil, daß sich auf den Silizidschichten im Vergleich zu reinem SiO2 niedriger schmelzende Oxidgemische bilden, sodaß derartige Überzugsschichten gute Rißheileigenschaften aufweisen und die Oberfläche des hochschmelzenden Metalles über einen weiten Temperaturbereich schützen. Die Aufbringung der Oxidationsschutzschichten kann durch die unterschiedlichsten Beschichtungsverfahren, wie Plasmaspritzen, Elektrophorese, Schmelzflußelektrolyse, Schmelztauchverfahren, CVD- oder PVD-Verfahren, durch Aufbringen eines Schlickers der gewünschten Pulvermischung auf die Oberfläche des hochschmelzenden Metalles (Slurry-Beschichtung) oder durch Auslagern des hochschmelzenden Metalles in einer entsprechenden Pulvermischung mit Aktivator (Pack cementation) erfolgen. Im Anschluß daran erfolgt im Falle der NiedertemperaturBeschichtungsverfahren eine Diffusionsglühbehandlung bei Temperaturen zwischen 1200°C und 1600°C unter Schutzgas oder im Hochvakuum zur Ausbildung der Silizidschichten. Bei den Hochtemperatur-Beschichtungsverfahren (Schmelzflußelektrolyse, Schmelztauchverfahren, CVD-Verfahren, pack cementation und in der Regel auch Plasmaspritzen) werden ausreichend dichte Schichten abgeschieden, so daß sich die Silizidschichten während der Oxidation im Einsatz bilden können, ohne daß Sauerstoff in größerem Ausmaß eindringen kann.The use of modified coatings based on silicon has the advantage that, compared to pure SiO 2, lower melting oxide mixtures form on the silicide layers, so that such coating layers have good crack-healing properties and protect the surface of the high-melting metal over a wide temperature range. The oxidation protection layers can be applied by a wide variety of coating processes, such as plasma spraying, electrophoresis, melt flow electrolysis, melt immersion processes, CVD or PVD processes, by applying a slip of the desired powder mixture to the surface of the refractory metal (slurry coating) or by outsourcing the refractory metal in a corresponding powder mixture with activator (pack cementation). Subsequently, in the case of the low-temperature coating process, a diffusion treatment is carried out at temperatures between 1200 ° C and 1600 ° C under protective gas or in a high vacuum to form the silicide layers. In the high-temperature coating processes (melt flow electrolysis, hot-dip process, CVD process, pack cementation and generally also plasma spraying), sufficiently dense layers are deposited so that the silicide layers can form during the oxidation without oxygen being able to penetrate to a greater extent .

Nachteilig bei diesen bekannten Oxidationsschutzschichten ist aber doch, daß sie oftmals nicht sehr gut haften und auch eine gewisse Porosität und Ungleichmäßigkeit aufweisen.However, a disadvantage of these known oxidation protection layers is that they often do not adhere very well and also have a certain porosity and Exhibit unevenness.

Die US Patentschrift Nr. 5 246 736 beschreibt ein Verfahren, gemäß dem ein Refraktär-Verbundmaterial, in dem oder auf dessen Oberfläche als Korrosionsschutz ein ternäres "Silizium-Bor-Kohlenstoff-System" mit gleichförmiger Elementenverteilung ein- bzw. aufgebracht wird. Die Borkonzentration in diesem Si-B-C-System soll nicht weniger als 5 Atom-% betragen. U.S. Patent No. 5,246,736 describes a method according to which a Refractory composite material in or on the surface of which Corrosion protection using a ternary "silicon-boron-carbon system" uniform distribution of elements is applied or applied. The Boron concentration in this Si-B-C system should not be less than 5 atomic% be.

Das Refraktär-Verbundmaterial besteht aus faserigen Verstärkungselementen, die in einer Matrix eingebettet und verdichtet sind, wobei laut Beschreibung die Fasern generell aus Kohlenstoff oder Keramik, wie Siliziumkarbid, bestehen. Die Matrix besteht aus Kohlenstoff oder zumindest teilweise aus SiC.The refractory composite material consists of fibrous reinforcing elements, which are embedded and compressed in a matrix, whereby loud Description of the fibers generally made of carbon or ceramic, such as Silicon carbide. The matrix consists of carbon or at least partly made of SiC.

Aufgabe der vorliegenden Erfindung ist es daher, eine Oxidationsschutzschicht für hochschmelzende Metalle zu schaffen, die eine verbesserte Schichthaftung, Gleichmäßigkeit und Dichtheit und damit einen deutlich verbesserten Oxidationsschutz gegenüber bisher bekannten Oxidationsschutzschichten aufweist.The object of the present invention is therefore an oxidation protection layer for high-melting metals to create an improved layer adhesion, Uniformity and tightness and thus a significantly improved Protection against oxidation compared to previously known oxidation protection layers having.

Erfindungsgemäß wird dies dadurch erreicht, daß die Oxidationsschutzschicht neben Bor und Silizium 0,1 - 4 Gew.% Kohlenstoff enthält. This is achieved according to the invention in that the oxidation protection layer contains 0.1 - 4% by weight of carbon in addition to boron and silicon.

Besonders bewährt hat sich dabei eine Oxidationsschutzschicht, die aus 5 bis 12 Gew.% Bor, 0,5 bis 3 Gew.% Kohlenstoff, Rest Silizium besteht.An oxidation protection layer consisting of 5 to 12% by weight boron, 0.5 to 3% by weight carbon, balance silicon.

Die erfindungsgemäße Oxidationsschutzschicht hat sich sowohl für massive Substrate aus hochschmelzenden Metallen als auch für Zwischenschichten aus diesen Werkstoffen hervorragend bewährt.
Es war völlig überraschend und in diesem Ausmaß nicht zu erwarten, daß durch derartig geringfügige Kohlenstoff-Anteile in der Oxidationsschutzschicht Verbesserungen in der Oxidationsbeständigkeit erreicht werden konnten, die gegenüber reinen Bor-Siliziumschichten für gewisse Einsatzbedingungen bis zum Faktor 2 gehen können. Der zur Herstellung der Schutzschicht zugegebene Kohlenstoff dient offensichtlich nicht nur als Legierungselement, sondern auch als Aktivator, der bei der Hochtemperatur-Beschichtung, bei der Wärmebehandlung oder auch in der ersten Zeit des Einsatzes in oxidierender Atmosphäre diffusionshemmenden Sauerstoff in Form von CO oder CO2 entfernt, was daran zu erkennen war, daß der Kohlenstoff-Gehalt in der wärmebehandelten bzw. bei der bereits kurzzeitig bei erhöhter Temperatur im Einsatz befindlichen Oxidationsschutzschicht bis zu einem Faktor 10 geringer ist als die ursprünglich aufgebrachte Menge von Kohlenstoff. Dieser anfänglich verringerte Kohlenstoff-Anteil stabilisiert sich dann und bleibt bis zum Versagen der Oxidationsschutzschicht weitgehend konstant.The oxidation protection layer according to the invention has proven itself extremely well both for massive substrates made of high-melting metals and for intermediate layers made of these materials.
It was completely surprising and to this extent not to be expected that such small amounts of carbon in the oxidation protection layer could result in improvements in the oxidation resistance, which can go up to a factor of 2 compared to pure boron silicon layers for certain conditions of use. The carbon added to produce the protective layer obviously serves not only as an alloying element, but also as an activator that removes diffusion-inhibiting oxygen in the form of CO or CO 2 during high-temperature coating, during heat treatment or even in the first period of use in an oxidizing atmosphere , which could be recognized from the fact that the carbon content in the heat-treated or in the oxidation protection layer that was already in use for a short time at elevated temperature is up to a factor of 10 less than the originally applied amount of carbon. This initially reduced carbon content then stabilizes and remains largely constant until the oxidation protection layer fails.

Die spezielle oxidationsverbessernde Wirkung des Kohlenstoffes war in keiner Weise vorhersehbar, da für den Fachmann durch den Kohlenstoff in erster Linie eine Karburierung des Substratmaterials zu erwarten war.
Die in der Praxis interessanten Schichtstärken der erfindungsgemäßen Oxidationsschutzschicht liegen in einem Bereich zwischen 50 µm und 500 µm. In einer besonders bevorzugten Ausgestaltung der Oxidationsschutzschicht haben sich Schichtstärken zwischen 100 und 300 µm bewährt. The special oxidation-improving effect of the carbon was in no way foreseeable, since the carbonization of the substrate material was primarily to be expected for the person skilled in the art.
The layer thicknesses of the oxidation protection layer according to the invention which are of interest in practice lie in a range between 50 μm and 500 μm. In a particularly preferred embodiment of the oxidation protection layer, layer thicknesses between 100 and 300 μm have proven successful.

Die Herstellung erfindungsgemäßer Oxidationsschutzschichten ist im Prinzip mit allen bekannten Beschichtungsverfahren möglich.
Das atmosphärische Plasmaspritzen und das Schlickerverfahren haben sich jedoch als besonders vorteilhafte Beschichtungsverfahren bewährt.The production of oxidation protection layers according to the invention is in principle possible with all known coating processes.
However, atmospheric plasma spraying and the slip process have proven to be particularly advantageous coating processes.

Im folgenden wird die Erfindung anhand von Herstellungsbeispielen näher erläutert.The invention will be explained in more detail below with the aid of production examples explained.

BEISPIEL 1:EXAMPLE 1:

Zylindrische Probekörper mit 10 - 25 mm Durchmesser und 50 - 250 mm Länge aus Molybdän wurden an der Oberfläche sandgestrahlt und alle scharfen Kanten verrundet. Eine Pulvermischung aus 880 g Siliziumpulver, 100 g Borpulver und 20 g Kohlenstoffpulver wurde im Taumelmischer 30 Minuten gemischt. Dann wurde durch Zugabe von 560 ml eines farblosen Nitrolackes, gelöst in 140 ml Nitroverdünnung, und vierstündiger Homogenisierung der Mischung im Taumelmischer ein entsprechender Schlicker hergestellt. Die Probekörper wurden durch Besprühen mit Schlicker beschichtet. Nach einer Lufttrocknung von 24 Stunden wurden die Probekörper bei 1370°C einer Schutzgasglühung (H2,1 bar) während 2 Stunden unterworfen, wodurch die Lackanteile des Schlickers vollständig entfernt wurden. Anschließend wurden die Probekörper von schlechthaftenden Schlickerresten befreit und optisch auf Schichtfehler, wie Risse oder Abplatzungen, geprüft und ggf. neuerlich beschichtet. Die derartig beschichteten Probekörper wiesen Schichtdicken im Bereich zwischen 50 und 100 µm auf. Zur Überprüfung der Oxidationsbeständigkeit wurden die beschichteten Probekörper bei 1200°C an Luft geglüht, wobei eine durchschnittliche Standzeit von 3000 Stunden bis zum Ausfall der Oxidationsschutzschicht festgestellt werden konnte. Zum Vergleich wurden Probekörper auf gleiche Weise mit einem Schlicker gleicher Zusammensetzung, aber ohne Kohlenstoff-Anteile beschichtet und ebenfalls bei 1200°C an Luft getestet. Bei den derartig beschichteten Probekörpern konnte eine durchschnittliche Standzeit von nur etwa 2000 Stunden festgestellt werden. Cylindrical test specimens with a diameter of 10 - 25 mm and a length of 50 - 250 mm made of molybdenum were sandblasted on the surface and all sharp edges were rounded. A powder mixture of 880 g silicon powder, 100 g boron powder and 20 g carbon powder was mixed in a tumble mixer for 30 minutes. A corresponding slip was then prepared by adding 560 ml of a colorless nitro lacquer, dissolved in 140 ml of nitro thinner, and homogenizing the mixture in a tumble mixer for four hours. The test specimens were coated with slurry by spraying. After air drying for 24 hours, the test specimens were subjected to protective gas annealing (H 2 , 1 bar) at 1370 ° C. for 2 hours, as a result of which the paint components of the slip were completely removed. The test specimens were then freed from poorly adhering slip residues and optically checked for layer defects such as cracks or flaking and, if necessary, coated again. The specimens coated in this way had layer thicknesses in the range between 50 and 100 μm. To check the resistance to oxidation, the coated test specimens were annealed in air at 1200 ° C., whereby an average service life of 3000 hours until the oxidation protection layer failed. For comparison, test specimens were coated in the same way with a slip of the same composition, but without carbon components, and also tested in air at 1200 ° C. With the specimens coated in this way, an average service life of only about 2000 hours could be determined.

BEISPIEL 2:EXAMPLE 2:

Plattenförmige Probekörper mit den Abmessungen 300 mm x 200 mm x 6 mm aus Molybdän wurden oberflächlich sandgestrahlt und alle Kanten und Ecken verrundet. Anschließend wurden die Probekörper durch atmosphärisches Plasmaspritzen beschichtet. Das verwendete Spritzpulver wurde dabei folgendermaßen hergestellt: 8,8 kg Siliziumpulver, 1,0 kg Borpulver und 0,2 kg Kohlenstoffpulver wurden gemischt, anschließend unter Wasserstoff bei 1350 - 1380°C während 3,5 Stunden gesintert und daraus eine Pulverfraktion mit einem Komgrößenbereich zwischen 36 und 120 µm ausgesiebt. Das Plasmaspritzen selbst erfolgte mit üblichen Einstellungen auf eine durchschnittliche Schichtdicke von 250 - 300 µm, die in mehrmaligen Spritzgängen erreicht wurde. Bei einem Glühen der Proben bei 1400°C an Luft wurde eine durchschnittliche Standzeit von 300 Stunden erreicht.Plate-shaped test specimens with the dimensions 300 mm x 200 mm x 6 mm Molybdenum was sandblasted on the surface and all edges and corners rounded. Then the test specimens were removed by atmospheric Plasma spray coated. The wettable powder used was manufactured as follows: 8.8 kg silicon powder, 1.0 kg boron powder and 0.2 kg Carbon powders were mixed, then under hydrogen at 1350 - 1380 ° C sintered for 3.5 hours and a powder fraction with a Grain size range between 36 and 120 µm sieved. Plasma spraying itself was done with the usual settings for an average layer thickness of 250 - 300 µm, which was achieved in multiple spray passes. At a Annealing of the samples at 1400 ° C in air resulted in an average tool life of 300 hours reached.

BEISPIEL 3:EXAMPLE 3

Plattenförmige Proben, wie nach Beispiel 2, jedoch aus Wolfram, wurden mit demselben Spritzpulver und denselben Bedingungen wie nach Beispiel 2 beschichtet. Bei einem Glühen der derart beschichteten Proben bei 1400°C an Luft wurde eine durchschnittliche Standzeit von 200 Stunden erreicht.Plate-like samples, as in Example 2, but made of tungsten, were also used the same wettable powder and the same conditions as in Example 2 coated. When the samples coated in this way glow at 1400 ° C Air reached an average life of 200 hours.

Claims (5)

  1. A substrate of a high-melting-point metal from the group comprising molybdenum, tungsten, tantalum, niobium and their alloys or composites thereof, with oxidation protection layer applied thereto, said layer consisting substantially of silicon and 1 - 14 wt.% boron
    characterised in that
    the protective layer additionally contains 0.1 - 4 wt.% carbon.
  2. A substrate with oxidation protection layer according to claim 1, characterised in that the layer consists of 5 - 12 wt.% boron and 0.5 - 3 wt.% carbon, the rest being silicon.
  3. A substrate with oxidation protection layer according to claim 1 or claim 2, characterised in that the layer is between 100 and 300 µm thick.
  4. A substrate with oxidation protection layer according to any one of claims 1 to 3, characterised in that the layer is produced by atmospheric plasma spraying.
  5. A substrate with oxidation protection layer according to any one of claims 1 to 3, characterised in that the layer is produced by a slurry method.
EP97200888A 1996-03-27 1997-03-24 Layer for protection against oxydation Expired - Lifetime EP0798402B1 (en)

Applications Claiming Priority (2)

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AT170/96 1996-03-27
AT0017096U AT1251U1 (en) 1996-03-27 1996-03-27 OXIDATION PROTECTIVE LAYER

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EP0798402B1 true EP0798402B1 (en) 1999-05-12

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Cited By (2)

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DE102007016411A1 (en) 2007-04-02 2008-10-09 Gfe Fremat Gmbh Semi-finished refractory metal product for producing ingot has protective layer giving protection against oxidation during hot deformation of semi-finished product
DE102007037592B3 (en) * 2007-08-06 2009-03-19 Gfe Fremat Gmbh Semi-finished product made of molybdenum or titanium, comprises oxygen-tight, transformable protective layer based on aluminum silicate and formed in situ from suspension applied on the semi-finished product at thermoforming temperature

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DE102007016411A1 (en) 2007-04-02 2008-10-09 Gfe Fremat Gmbh Semi-finished refractory metal product for producing ingot has protective layer giving protection against oxidation during hot deformation of semi-finished product
DE102007037592B3 (en) * 2007-08-06 2009-03-19 Gfe Fremat Gmbh Semi-finished product made of molybdenum or titanium, comprises oxygen-tight, transformable protective layer based on aluminum silicate and formed in situ from suspension applied on the semi-finished product at thermoforming temperature

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DE59700159D1 (en) 1999-06-17
AT1251U1 (en) 1997-01-27
EP0798402A1 (en) 1997-10-01
JPH1053854A (en) 1998-02-24
JP4064490B2 (en) 2008-03-19
US5776550A (en) 1998-07-07
ES2135281T3 (en) 1999-10-16

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