EP0906967B1 - Application of an alloy from aluminium and titanium - Google Patents
Application of an alloy from aluminium and titanium Download PDFInfo
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- EP0906967B1 EP0906967B1 EP98117583A EP98117583A EP0906967B1 EP 0906967 B1 EP0906967 B1 EP 0906967B1 EP 98117583 A EP98117583 A EP 98117583A EP 98117583 A EP98117583 A EP 98117583A EP 0906967 B1 EP0906967 B1 EP 0906967B1
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- alloy
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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
Definitions
- the invention relates to the use of an alloy made of aluminum and titanium.
- Alloys of aluminum and titanium are known to be particularly corrosion-resistant in technology as well as at high temperatures.
- the measurement results given in this document result in a material removal of 105 ⁇ m after 100 hours or 4.4 mm after one year in the atmosphere mentioned, which is generally not acceptable for technical systems.
- DE-A-42 15 017 describes a titanium-aluminum alloy as a material for, for example, turbine blades. When used at high temperatures up to 900 ° C, the material should become resistant to oxidation and corrosion by forming a slowly growing Al 2 O 3 layer instead of a rapidly growing TiO 2 layer.
- EP-A-0 495 454 also describes a material made of aluminum and titanium, in which a protective layer made of Al 2 O 3 is intended to prevent corrosion of the material.
- the proposed aluminum-titanium alloy is intended as a material for engine parts - in particular valves and piston pins.
- EP 0 716 154 A2 describes an aluminum-titanium alloy, which is suitable for plants with process gases, which due to their content of sulfur-containing compounds act sulfidizing.
- the process gas that the Alloy exposed in accordance with this document has one Carbon activity compared to the corrosion effect a subordinate due to the sulfur-containing compounds Role that is not discussed in the Scriptures becomes.
- Metal dusting is a form of corrosion attack that can take place in gases with high carbon and low oxygen activities. Such environments are mainly found in the petrochemical industry in atmospheres with CO, CH 4 and higher hydrocarbons or in gas mixtures with high carbon activities. Metal dusting phenomena have also been observed in coal gasification atmospheres, but do not pose a general problem there. However, metal dusting can cause such massive damage that the plants can no longer be operated. This affected, for example, sootblower elements made of steels type 347 and 310 in waste heat boilers of synthesis gas reactors, the synthesis gas (essentially CO and H 2 with some water vapor and carbon particles) being produced by the combustion of methane with oxygen.
- sootblower elements made of steels type 347 and 310 in waste heat boilers of synthesis gas reactors, the synthesis gas (essentially CO and H 2 with some water vapor and carbon particles) being produced by the combustion of methane with oxygen.
- the metal removal took place in a temperature range from 480 ° C to 900 ° C, and massive damage was already observed after 3 weeks of use. Further examples can be found in connection with the operation of reformer plants, where a synthesis gas is produced from H 2 + CO for the production of methanol. Strong attack was observed in the temperature range from 650 ° C to 725 ° C. Metal dusting problems also occurred in hydrodealkylation plants, in acetic acid cracking plants and in coal gasification plants. Other examples are the failure of waste heat boilers in ammonia plants and in plants in the heat treatment industry.
- the Metal Dusting attack is either in form a strong local crater formation in the metallic material or in the form of larger attacked areas Areas up to the even removal of the Metal. In all cases, carburization occurs first the edge zone, followed by material decay on the surface in the form of powder formation from a powder mixture of carbon, carbides, Metal particles and occasionally oxide particles. Since this Powder does not have its own mechanical strength it is usually carried away by the gas flow in the system, so that deep damage in the attack points Material can be observed. Affected by this form of attack are practically all conventional technical Materials including simple carbon steels, the usual heat-resistant chrome-molybdenum steels, high-alloy steels and high-alloy iron and Nickel-based materials. As a remedy in the literature the use of materials with very high chrome contents or with corresponding silicon contents proposed. As now very extensive Studies show are despite these recommendations no reliable material solutions available.
- protective oxide layers would be able to the process of metal dusting (i.e. catastrophic To prevent carburization) if they have a corresponding Can develop protective effect on the material surface. Since it is in the atmospheres where metal Dusting occurs to those with extremely low oxygen partial pressures and high carbon activities extremely stable oxides would have the potential offer to build up a protective layer.
- Preoxidation of conventional materials, as occasionally used in the Literature proposed does not lead to permanent Success because the oxide layers under operating conditions at least locally, if not globally, damaged can be and possibly in atmospheres with temporal changing compositions also their stability can lose.
- Particularly stable oxides are aluminum oxide, Silicon oxide and titanium oxide. A stimulation of the Silicon oxide formation by alloying accordingly higher Silicon levels for the alloys were already in the Literature suggested.
- the problem underlying the invention is an advantageous use of an alloy of aluminum and find Titan.
- the solution to the first problem is to use it an alloy of aluminum and titanium as high temperature resistant, corrosion resistant coating material for heat-resistant steel to protect against corrosion in plants with process gases which have a very low Partial pressure of oxygen ("reducing" atmospheres) and because of their content of carbon compounds have a carbon activity greater than 1.
- the invention is based on the idea that a protective layer, a carburizing under the conditions mentioned of the material can only prevent by extreme stable oxides can be achieved.
- a protective layer a carburizing under the conditions mentioned of the material can only prevent by extreme stable oxides can be achieved.
- a protective effect can therefore only be achieved if on an inexpensive metallic substrate appropriate protective layer is applied, its alloy properties the formation of such cover layers allow.
- the use of materials for such Protective layers as the solid material of the component separates for cost reasons as well as for manufacturing reasons and dimensional reasons.
- an inexpensive metallic base material in the form of an unalloyed or low-alloy heat-resistant Steel up to higher alloyed steels with a corresponding Combine corrosion protection coating.
- This anti-corrosion coating is based on the elements Titanium and aluminum, both extremely stable oxides can train in reaction with the process environment and thus are able to provide an oxide protective layer build. Even if this is violated The injured is healed again during the shift Ask because even the low oxygen levels the process environment are able to get this stable again To form oxides. This way it can be permanent Protective effect by applying the coating to a corresponding one inexpensive substrate can be achieved. benefits this corrosion protection coating also results moreover by the value of the coefficient of thermal expansion, of the same order of magnitude lies like that of unalloyed and low-alloyed or ferritic Chromium steels. For this reason, when there are temperature changes no noteworthy layer tensions induced, the others to tear or flake off of the protective coating.
- Metal dusting conditions were simulated in a laboratory in a retort.
- a gas mixture of 75% H 2 and 25% CO was used, which has a carbon activity greater than 1 at the test temperature of 650 ° C, so that graphite is deposited on the surface of the samples used in the retort.
- a low-alloy, heat-resistant steel of type 13CrMo44 in the uncoated state the same steel with an APS layer of type Ti48Al1.5Cr and the coating material alone were tested. After aging at 650 ° C in the above atmosphere for approx. 100 h, the uncoated steel showed massive metal dusting attack. The coating material was practically not attacked; only tarnishing colors were visible in some places.
- the coating also proved to be durable. Metal dusting attack on the underlying steel occurred at most from the corners and edges of the samples (the samples were only coated on one surface) or at places where the layer still had open porosity. The latter could still occur because the coating process had not yet been optimized with regard to the gas tightness of the layers.
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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
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- Organic Chemistry (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Coating With Molten Metal (AREA)
Description
Die Erfindung betrifft eine Verwendung einer Legierung aus Aluminium und Titan.The invention relates to the use of an alloy made of aluminum and titanium.
Legierungen aus Aluminium und Titan sind in der Technik als auch bei hohen Temperaturen besonders korrosionsfest bekannt. Das Dokument Advanced Materials 1993, 1/A: Ceramics, Powders and Advanced Processing, Transactions Materials Research Society of Japan, vol. 14A, 1994, Seiten 233 - 238, beschreibt beispielsweise die Verwendung einer Aluminium-Titan-Legierung in einer Atmosphäre aus H2S und H2. Aus den in dieser Schrift angegebenen Messergebnissen ergibt sich in der genannten Atmosphäre ein Materialabtrag von 105 µm nach 100 Stunden oder 4,4 mm nach einem Jahr, was für technische Anlagen in aller Regel nicht hinnehmbar ist.Alloys of aluminum and titanium are known to be particularly corrosion-resistant in technology as well as at high temperatures. The document Advanced Materials 1993, 1 / A: Ceramics, Powders and Advanced Processing, Transactions Materials Research Society of Japan, vol. 14A, 1994, pages 233-238, describes, for example, the use of an aluminum-titanium alloy in an atmosphere of H 2 S and H 2 . The measurement results given in this document result in a material removal of 105 µm after 100 hours or 4.4 mm after one year in the atmosphere mentioned, which is generally not acceptable for technical systems.
Die DE-A-42 15 017 beschreibt eine Titan-Aluminium-Legierung als Werkstoff für beispielsweise Turbinenschaufeln. Der Werkstoff soll bei Hochtemperatureinsatz bis zu 900°C dadurch eine Oxidations- und Korrosionsbeständigkeit erlangen, dass sich statt einer schnellwachsenden TiO2-Schicht eine langsam wachsende Al2O3-Schicht bildet.DE-A-42 15 017 describes a titanium-aluminum alloy as a material for, for example, turbine blades. When used at high temperatures up to 900 ° C, the material should become resistant to oxidation and corrosion by forming a slowly growing Al 2 O 3 layer instead of a rapidly growing TiO 2 layer.
Die EP-A-0 495 454 beschreibt ebenfalls einen Werkstoff aus Aluminium und Titan, bei dem eine Schutzschicht aus Al2O3 eine Korrosion des Werkstoffs verhindern soll. Die vorgeschlagene Aluminium-Titanlegierung ist als Werkstoff für Motorenteile - insbesondere Ventile und Kolbenstifte - bestimmt.EP-A-0 495 454 also describes a material made of aluminum and titanium, in which a protective layer made of Al 2 O 3 is intended to prevent corrosion of the material. The proposed aluminum-titanium alloy is intended as a material for engine parts - in particular valves and piston pins.
Die EP 0 716 154 A2 beschreibt eine Aluminium-Titan-Legierung, die sich für Anlagen mit Prozessgasen eignet, welche aufgrund ihres Gehaltes an schwefelhaltigen Verbindungen sulfidierend wirken. Das Prozessgas, dem die Legierung gemäß diesem Dokument ausgesetzt wird, hat eine Kohlenstoffaktivität, die im Vergleich zur Korrosionswirkung durch die schwefelhaltigen Verbindungen eine untergeordnete Rolle spielt, auf die in der Schrift nicht eingegangen wird.EP 0 716 154 A2 describes an aluminum-titanium alloy, which is suitable for plants with process gases, which due to their content of sulfur-containing compounds act sulfidizing. The process gas that the Alloy exposed in accordance with this document has one Carbon activity compared to the corrosion effect a subordinate due to the sulfur-containing compounds Role that is not discussed in the Scriptures becomes.
Seit Mitte der 50er Jahre wird in der Literatur über Korrosion durch Metal Dusting berichtet. Metal Dusting ist eine Form des Korrosionsangriffs, die in Gasen mit hohen Kohlenstoff- und niedrigen Sauerstoffaktivitäten stattfinden kann. Solche Umgebungen werden vor allem in der petrochemischen Industrie in Atmosphären mit CO, CH4 und höheren Kohlenwasserstoffen bzw. in Gasmischungen mit hohen Kohlenstoffaktivitäten angetroffen. Metal Dusting Phänomene wurden darüber hinaus auch in Kohlevergasungsatmosphären beobachtet, stellen dort jedoch kein generelles Problem dar. Durch Metal Dusting können allerdings solch massive Schäden auftreten, dass die Anlagen nicht mehr weiter betrieben werden können. Betroffen hiervon waren z.B. Rußbläserelemente aus den Stählen Typ 347 und 310 in Abhitzekesseln von Synthesegasreaktoren, wobei das Synthesegas (im Wesentlichen CO und H2 mit etwas Wasserdampf und Kohlenstoffpartikeln) durch die Verbrennung von Methan mit Sauerstoff produziert wurde. Der Metallabtrag fand in einem Temperaturbereich von 480°C bis 900°C statt, und massive Schäden wurden bereits nach 3 Wochen Einsatz beobachtet. Weitere Beispiele finden sich im Zusammenhang mit dem Betrieb von Reformeranlagen, wo ein Synthesegas aus H2 + CO für die Methanolproduktion hergestellt wird. Starker Angriff wurde hierbei im Temperaturbereich von 650°C bis 725°C beobachtet. Metal Dusting Probleme traten darüber hinaus bei Hydrodealkylationsanlagen auf, bei Essigsäurecrackanlagen und in Kohlevergasungsanlagen. Andere Beispiele sind das Versagen von Abhitzekesseln in Ammoniakanlagen und in Anlagen der Wärmebehandlungsindustrie.Corrosion caused by metal dusting has been reported in the literature since the mid-1950s. Metal dusting is a form of corrosion attack that can take place in gases with high carbon and low oxygen activities. Such environments are mainly found in the petrochemical industry in atmospheres with CO, CH 4 and higher hydrocarbons or in gas mixtures with high carbon activities. Metal dusting phenomena have also been observed in coal gasification atmospheres, but do not pose a general problem there. However, metal dusting can cause such massive damage that the plants can no longer be operated. This affected, for example, sootblower elements made of steels type 347 and 310 in waste heat boilers of synthesis gas reactors, the synthesis gas (essentially CO and H 2 with some water vapor and carbon particles) being produced by the combustion of methane with oxygen. The metal removal took place in a temperature range from 480 ° C to 900 ° C, and massive damage was already observed after 3 weeks of use. Further examples can be found in connection with the operation of reformer plants, where a synthesis gas is produced from H 2 + CO for the production of methanol. Strong attack was observed in the temperature range from 650 ° C to 725 ° C. Metal dusting problems also occurred in hydrodealkylation plants, in acetic acid cracking plants and in coal gasification plants. Other examples are the failure of waste heat boilers in ammonia plants and in plants in the heat treatment industry.
Der Metal Dusting Angriff äußert sich entweder in Form einer starken lokalen Kraterbildung im metallischen Werkstoff oder in Form von größeren eher flächenhaft angegriffenen Bereichen bis hin zum gleichmäßigen Abtrag des Metalls. In allen Fällen tritt zunächst eine starke Aufkohlung der Randzone auf, gefolgt von einem Werkstoffzerfall an der Oberfläche in Form von Pulverbildung, bestehend aus einer Pulvermischung von Kohlenstoff, Carbiden, Metallpartikeln und gelegentlich Oxidteilchen. Da dieses Pulver keine eigene mechanische Festigkeit besitzt, wird es in der Regel vom Gasstrom in der Anlage weggetragen, so dass an den Angriffsstellen eine tiefe Schädigung im Werkstoff zu beobachten ist. Betroffen von dieser Angriffsform sind praktisch alle konventionellen technischen Werkstoffe einschließlich der einfachen Kohlenstoffstähle, der üblichen warmfesten Chrom-Molybdän-Stähle, der hochlegierten Stähle und der hochlegierten Eisenund Nickel-Basis-Werkstoffe. Als Abhilfemaßnahmen werden in der Literatur die Verwendung von Werkstoffen mit sehr hohen Chromgehalten bzw. mit entsprechenden Siliziumgehalten vorgeschlagen. Wie mittlerweile sehr umfangreiche Untersuchungen zeigen, sind trotz dieser Empfehlungen keine zuverlässigen Werkstofflösungen vorhanden.The Metal Dusting attack is either in form a strong local crater formation in the metallic material or in the form of larger attacked areas Areas up to the even removal of the Metal. In all cases, carburization occurs first the edge zone, followed by material decay on the surface in the form of powder formation from a powder mixture of carbon, carbides, Metal particles and occasionally oxide particles. Since this Powder does not have its own mechanical strength it is usually carried away by the gas flow in the system, so that deep damage in the attack points Material can be observed. Affected by this form of attack are practically all conventional technical Materials including simple carbon steels, the usual heat-resistant chrome-molybdenum steels, high-alloy steels and high-alloy iron and Nickel-based materials. As a remedy in the literature the use of materials with very high chrome contents or with corresponding silicon contents proposed. As now very extensive Studies show are despite these recommendations no reliable material solutions available.
Grundsätzlich wären schützende Oxidschichten in der Lage, den Vorgang des Metal Dusting (d.h. eine katastrophale Aufkohlung) zu verhindern, wenn sie eine entsprechende Schutzwirkung auf der Werkstoffoberfläche entfalten könnten. Da es sich bei den Atmosphären, in denen Metal Dusting auftritt, um solche mit extrem niedrigen Sauerstoffpartialdrücken und hohen Kohlenstoffaktivitäten handelt, würden vor allem extrem stabile Oxide das Potential bieten, eine Schutzschicht aufzubauen. Voroxidation von konventionellen Werkstoffen, wie sie gelegentlich in der Literatur vorgeschlagen wird, führt nicht zu einem dauerhaften Erfolg, da unter Betriebsbedingungen die Oxidschichten zumindest lokal, wenn nicht sogar global geschädigt werden können und evtl. in Atmosphären mit zeitlich wechselnden Zusammensetzungen auch ihre Stabilität verlieren können. Besonders stabile Oxide sind Aluminiumoxid, Siliziumoxid und Titanoxid. Eine Stimulierung der Siliziumoxidbildung durch Zulegieren entsprechend hoher Siliziumgehalte zu den Legierungen wurde bereits in der Literatur vorgeschlagen. Eine Bestätigung des positiven Siliziumeffekts ist in der Literatur allerdings nicht zu finden. Grundsätzlich würde die Bildung von Aluminiumoxid die Aufkohlungsbeständigkeit erhöhen können, so dass es naheliegend wäre, Werkstoffe mit hohen Aluminiumgehalten zu verwenden. Bei Temperaturen unterhalb von 900°C bildet sich jedoch auf den konventionellen aluminiumlegierten Eisen- und Nickel-Basis-Legierungen noch keine geschlossene Aluminiumoxidbarriere aus, so dass die Schutzwirkung auf Temperaturen oberhalb von 900°C beschränkt bleibt, wo diese auch technisch genutzt wird. Titanoxid als Deckschichtbildner wurde bisher nicht angedacht und würde auch erst bei Titanbasiswerkstoffen in diesem Temperaturbereich möglich sein.In principle, protective oxide layers would be able to the process of metal dusting (i.e. catastrophic To prevent carburization) if they have a corresponding Could develop protective effect on the material surface. Since it is in the atmospheres where metal Dusting occurs to those with extremely low oxygen partial pressures and high carbon activities extremely stable oxides would have the potential offer to build up a protective layer. Preoxidation of conventional materials, as occasionally used in the Literature proposed does not lead to permanent Success because the oxide layers under operating conditions at least locally, if not globally, damaged can be and possibly in atmospheres with temporal changing compositions also their stability can lose. Particularly stable oxides are aluminum oxide, Silicon oxide and titanium oxide. A stimulation of the Silicon oxide formation by alloying accordingly higher Silicon levels for the alloys were already in the Literature suggested. A confirmation of the positive Silicon effect is however not to be found in the literature Find. Basically, the formation of alumina can increase the carburization resistance so that it would be obvious materials with high aluminum contents to use. Forms at temperatures below 900 ° C However, the conventional aluminum alloy Iron and nickel-based alloys are not yet closed Aluminum oxide barrier, so that the protective effect remains limited to temperatures above 900 ° C where this is also used technically. Titanium oxide as a top layer has not been considered and would even with titanium base materials in this temperature range to be possible.
Das der Erfindung zugrundeliegende Problem besteht darin, eine vorteilhafte Verwendung einer Legierung aus Aluminium und Titan aufzufinden. The problem underlying the invention is an advantageous use of an alloy of aluminum and find Titan.
Die Lösung des erstgenannten Problems besteht in der Verwendung einer Legierung aus Aluminium und Titan als hochtemperaturbeständiger, korrosionsfester Beschichtungswerkstoff für warmfesten Stahl zum Schutz vor Korrosion in Anlagen mit Prozessgasen, welche einen sehr niedrigen Sauerstoffpartialdruck ("reduzierende" Atmosphären) und auf Grund ihres Gehaltes an Kohlenstoffverbindungen eine Kohlenstoffaktivität größer als 1 aufweisen.The solution to the first problem is to use it an alloy of aluminum and titanium as high temperature resistant, corrosion resistant coating material for heat-resistant steel to protect against corrosion in plants with process gases which have a very low Partial pressure of oxygen ("reducing" atmospheres) and because of their content of carbon compounds have a carbon activity greater than 1.
Die Erfindung basiert auf der Idee, dass eine Schutzschicht, die unter den genannten Bedingungen eine Aufkohlung des Werkstoffs verhindern kann, nur durch extrem stabile Oxide zu erreichen ist. Wie bereits ausgeführt, ist über Legierungsmaßnahmen die Bildung solcher Schutzschichten nicht im genannten Temperaturbereich zu erzielen. Eine Schutzwirkung kann daher nur erreicht werden, wenn auf einem preiswerten metallischen Substrat eine entsprechende Schutzschicht aufgebracht wird, deren Legierungseigenschaften die Bildung solcher Deckschichten erlauben. Die Verwendung von Werkstoffen für solche Schutzschichten als Vollmaterial der Komponente scheidet sowohl aus Kostengründen als auch aus fertigungstechnischen und dimensionalen Gründen aus. Somit sieht die Erfindung vor, einen preiswerten metallischen Grundwerkstoff in Form eines un- oder niedriglegierten warmfesten Stahles bis hin zu höher legierten Stählen mit einer entsprechenden Korrosionsschutzbeschichtung zu kombinieren. Diese Korrosionsschutzbeschichtung basiert auf den Elementen Titan und Aluminium, die beide extrem stabile Oxide in der Reaktion mit der Prozessumgebung ausbilden können und damit in der Lage sind, eine oxidische Schutzschicht aufzubauen. Selbst bei einer Verletzung dieser Schicht im Betrieb erfolgt ein Wiederausheilen der verletzten Stellen, da selbst die geringen Sauerstoffgehalte der Prozessumgebung in der Lage sind, erneut diese stabilen Oxide zu bilden. Auf diese Weise kann eine dauerhafte Schutzwirkung durch Anwendung des Coatings auf ein entsprechendes preiswertes Substrat erzielt werden. Vorteile dieser Korrosionsschutzbeschichtung ergeben sich auch darüber hinaus durch den Wert des thermischen Ausdehnungskoeffizienten, der in der gleichen Größenordnung liegt wie der von un- und niedriglegierten bzw. von ferritischen Chromstählen. Aus diesem Grunde werden bei Temperaturwechseln keine nennenswerten Schichtspannungen induziert, die anderenfalls zum Aufreißen oder Abplatzen der Schutzbeschichtung führen würden.The invention is based on the idea that a protective layer, a carburizing under the conditions mentioned of the material can only prevent by extreme stable oxides can be achieved. As already stated is the formation of such protective layers via alloying measures not to be achieved in the specified temperature range. A protective effect can therefore only be achieved if on an inexpensive metallic substrate appropriate protective layer is applied, its alloy properties the formation of such cover layers allow. The use of materials for such Protective layers as the solid material of the component separates for cost reasons as well as for manufacturing reasons and dimensional reasons. Thus the invention sees before, an inexpensive metallic base material in the form of an unalloyed or low-alloy heat-resistant Steel up to higher alloyed steels with a corresponding Combine corrosion protection coating. This anti-corrosion coating is based on the elements Titanium and aluminum, both extremely stable oxides can train in reaction with the process environment and thus are able to provide an oxide protective layer build. Even if this is violated The injured is healed again during the shift Ask because even the low oxygen levels the process environment are able to get this stable again To form oxides. This way it can be permanent Protective effect by applying the coating to a corresponding one inexpensive substrate can be achieved. benefits this corrosion protection coating also results moreover by the value of the coefficient of thermal expansion, of the same order of magnitude lies like that of unalloyed and low-alloyed or ferritic Chromium steels. For this reason, when there are temperature changes no noteworthy layer tensions induced, the others to tear or flake off of the protective coating.
Metal Dusting Bedingungen wurden im Labor in einer Retorte simuliert. Hierzu wurde ein Gasgemisch aus 75% H2 und 25% CO verwendet, das bei der Versuchstemperatur von 650°C eine Kohlenstoffaktivität größer 1 besitzt, so dass es zur Graphitabscheidung auf der Oberfläche der in die Retorte eingesetzten Proben kommt. In den Versuchen wurden ein niedriglegierter warmfester Stahl von Typ 13CrMo44 im unbeschichteten Zustand, der gleiche Stahl mit einer APS-Schicht von Typ Ti48Al1.5Cr sowie der Beschichtungswerkstoff allein getestet. Nach einer Auslagerung bei 650°C in der o.g. Atmosphäre für ca. 100 h zeigte der unbeschichtete Stahl massiven Metal Dusting Angriff. Der Beschichtungswerkstoff wurde praktisch nicht angegriffen; es waren lediglich Anlauffarben an einigen Stellen zu sehen. Die Beschichtung erwies sich ebenfalls als beständig. Metal Dusting Angriff auf den darunterliegenden Stahl fand allenfalls von Ecken und Kanten der Proben her statt (die Proben waren nur auf einer Fläche beschichtet) bzw. an Stellen, wo die Schicht noch offene Porosität aufgewiesen hatte. Letztere konnte noch auftreten, da der Beschichtungsprozess noch nicht bezüglich der Gasdichtigkeit der Schichten optimiert worden war.Metal dusting conditions were simulated in a laboratory in a retort. For this purpose, a gas mixture of 75% H 2 and 25% CO was used, which has a carbon activity greater than 1 at the test temperature of 650 ° C, so that graphite is deposited on the surface of the samples used in the retort. In the tests, a low-alloy, heat-resistant steel of type 13CrMo44 in the uncoated state, the same steel with an APS layer of type Ti48Al1.5Cr and the coating material alone were tested. After aging at 650 ° C in the above atmosphere for approx. 100 h, the uncoated steel showed massive metal dusting attack. The coating material was practically not attacked; only tarnishing colors were visible in some places. The coating also proved to be durable. Metal dusting attack on the underlying steel occurred at most from the corners and edges of the samples (the samples were only coated on one surface) or at places where the layer still had open porosity. The latter could still occur because the coating process had not yet been optimized with regard to the gas tightness of the layers.
Claims (2)
- Use of an alloy of aluminium and titanium as a corrosion-proof coating material with high temperature stability for steel for high temperature service, to provide protection against corrosion in installations with process gases which have a very low oxygen partial pressure ("reducing" atmospheres) and a carbon activity greater than 1 due to their carbon compounds content.
- Use according to Claim 1, characterized in that the process gases have an oxygen partial pressure in the range from 1x10-50 Pa to 1x10-22 Pa, especially 1x10-29 Pa to 1x10-25, and heat the coating material to up to 700°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19743421 | 1997-10-01 | ||
| DE19743421 | 1997-10-01 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0906967A2 EP0906967A2 (en) | 1999-04-07 |
| EP0906967A3 EP0906967A3 (en) | 1999-05-19 |
| EP0906967B1 true EP0906967B1 (en) | 2003-11-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP98117583A Expired - Lifetime EP0906967B1 (en) | 1997-10-01 | 1998-09-16 | Application of an alloy from aluminium and titanium |
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| Country | Link |
|---|---|
| EP (1) | EP0906967B1 (en) |
| DE (1) | DE59810149D1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7422804B2 (en) | 2004-02-03 | 2008-09-09 | Exxonmobil Research And Engineering Company | Metal dusting resistant stable-carbide forming alloy surfaces |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4443147A1 (en) * | 1994-12-05 | 1996-06-27 | Dechema | Corrosion-resistant material for high-temperature applications in sulfidizing process gases |
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1998
- 1998-09-16 DE DE59810149T patent/DE59810149D1/en not_active Expired - Fee Related
- 1998-09-16 EP EP98117583A patent/EP0906967B1/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| EP0906967A3 (en) | 1999-05-19 |
| DE59810149D1 (en) | 2003-12-18 |
| EP0906967A2 (en) | 1999-04-07 |
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