EP1122330B1 - Process and use of an apparatus for nitrocarburizing of metallic parts - Google Patents
Process and use of an apparatus for nitrocarburizing of metallic parts Download PDFInfo
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- EP1122330B1 EP1122330B1 EP20000102360 EP00102360A EP1122330B1 EP 1122330 B1 EP1122330 B1 EP 1122330B1 EP 20000102360 EP20000102360 EP 20000102360 EP 00102360 A EP00102360 A EP 00102360A EP 1122330 B1 EP1122330 B1 EP 1122330B1
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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
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
- C23C8/30—Carbo-nitriding
- C23C8/32—Carbo-nitriding of ferrous surfaces
Definitions
- the invention relates to a method according to the preamble of claim 1.
- the invention further relates to the Use of a device for performing such a method.
- the surface layer is enriched with nitrogen by the ammonia (NH 3 ) contained in a reaction gas at temperatures of generally over 500 ° C under the catalytic effect of the surface of the workpieces to be nitrided decays into nitrogen (N) and hydrogen (H).
- the ammonia molecule is adsorbed and gradually degraded on the workpiece surface, whereby the required nitrogen is released in atomic form and is available for solution in iron and for the formation of iron nitride (Fe x N).
- the surface layer is simultaneously enriched with carbon.
- Atomic carbon (C) diffuses in an analogous manner through the workpiece surface into the surface layer.
- connection layer which, when nitriding or nitrocarburizing, mainly consists of hexagonal ⁇ -nitride (Fe 2-3 N) and face-centered cubic ⁇ '-nitride (Fe 4 N).
- connection layer which, when nitriding or nitrocarburizing, mainly consists of hexagonal ⁇ -nitride (Fe 2-3 N) and face-centered cubic ⁇ '-nitride (Fe 4 N).
- the carbon index K C for a reaction gas with a composition of 50% by volume ammonia (NH 3 ) and 50% by volume endogas which is usually used for nitrocarburizing with regard to an optimized content of ⁇ -nitride, has values between 1, 5 and 2.5, if the proportion of ammonia reacted during nitrocarburizing in the gas atmosphere is between 15% by volume and 40% by volume.
- the carbonization index K C is significantly lower for a reaction gas with a composition of 50% by volume NH 3 , 45% by volume N 2 and 5% by volume CO 2 .
- nitrocarburizing is carried out with a proportion of carbon dioxide in the gas atmosphere between 0 vol.% And 7 vol.% And a proportion of ammonia between 0 vol.% And 40 vol.%
- the carbonization index K C values between 0 and 0.5 on. Due to the by the formula: CO + H 2 O ⁇ CO 2 + H 2 described balance of the components carbon monoxide (CO), water vapor (H 2 O) D, carbon dioxide (CO 2) and hydrogen (H 2) in the gas atmosphere, the nitriding potential K N K C and the carburizing interdependent.
- the carbonization index K C can only be changed to a limited extent with a predetermined nitriding index K N and can therefore only be used to a limited extent to influence workpiece properties.
- a disadvantage is furthermore that the carburizing K C in the commonly used reaction gases has not sufficiently high values such that the influenced by the content of carbon in the bonding layer technical properties of metallic workpieces, such as wear resistance or corrosion resistance, not to the extent possible can be exploited.
- the invention is based on the object of developing a method for the heat treatment of metallic workpieces in such a way that an improved wear and corrosion resistance of the treated workpieces can be achieved.
- unsaturated hydrocarbons of the type C n H 2n preferably ethylene (C 2 H 4 ) or propylene (C 2 H 6 ).
- saturated hydrocarbons of the type C n H 2n + 2 preferably ethane (C 2 H 6 ) or propane (C 3 H 8 ). This is because thermal splitting of the saturated hydrocarbons during the course of the process can result in the formation of unsaturated hydrocarbons.
- the hydrocarbons can advantageously also be added only while they are kept at a certain temperature, preferably a nitriding temperature between 500 ° C. and 700 ° C. With regard to a process control optimized with regard to the required workpiece properties, it may also be expedient to add the hydrocarbons only at the end of the holding to the nitriding temperature.
- a particularly advantageous procedure is also given when the hydrocarbons are added discontinuously, for example only at certain times, which enables a process-adapted procedure.
- the invention according to the proposed limitation of the addition of hydrocarbons to a proportion of 3 vol.% To 25 vol.% Depending on the composition of the reaction gas offers the advantage that an increased separation of free carbon, which generally leads to undesired sooting, for example the interior of heat treatment furnaces , leads, is avoided.
- a reaction gas with a composition of 95% by volume ammonia (NH 3 ) and 5% by volume propane (C 3 H 8 ) is proposed, which can also be produced economically.
- 1 and 2 show the content of carbon w C and nitrogen w N of the connecting layer of two nitrocarburized workpiece samples as a function of the edge distance r of the connecting layer.
- the identical workpiece samples of the steel grade 16 Mn Cr 5 material no. 1.7131 were heated to a nitriding temperature of approx. 580 ° C in an ammonia-containing gas atmosphere of a chamber furnace.
- the volume flow of reaction gases G 1 , G 2 flowing through the chamber furnace was in each case approximately 4 m 3 / h. After approximately 180 minutes of nitrocarburizing, the samples were cooled to room temperature in a nitrogen atmosphere. The connection layer determined afterwards was approx. 16 ⁇ m - 18 ⁇ m.
- the depth profiles of carbon differ considerably from one another.
- the curve of the carbon content in the workpiece sample treated with the reaction gas G 2 lies considerably above the carbon content achieved with the reaction gas G 1 up to the middle of the connecting layer and only then takes a course that roughly matches this and is approximately parallel to the drop in the nitrogen content.
- the course of the carbon content in FIGS. 1 and 2 thus confirms that the addition of propane in the reaction gas G 2 produces a higher carbon content in the connecting layer, which results from a higher carbon index K C of the reaction gas G 2 and not least to one leads to improved wear and corrosion resistance of the workpiece sample.
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- Mechanical Engineering (AREA)
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Abstract
Description
Die Erfindung betrifft einVerfahren gemäß dem Oberbegriff des Anspruchs 1. Die Erfindung bezieht sich ferner auf die Verwendung einer Vorrichtung zur Durchführung eines solchen Verfahrens.The invention relates to a method according to the preamble of claim 1. The invention further relates to the Use of a device for performing such a method.
Gemäß der DE 197 19225 C1 ist es bekannt, dass zum Erzeugen von definierten Werkstückeigenschaften, wie etwa einer hohen Verschleißfestigkeit oder ausreichender Korrosionsbeständigkeit, metallische Werkstücke einer thermochemischen Wärmebehandlung unterzogen werden. Das Ergebnis der Wärmebehandlung ist etwa beim Nitrieren oder Nitrocarburieren die Anreicherung der Randschicht der Werkstücke mit Stickstoff und/oder Kohlenstoff, um hierdurch den Werkstücken die geforderten mechanischen und chemischen Eigenschaften an der Oberfläche und im Randbereich zu verleihen.According to DE 197 19225 C1 it is known that to create defined workpiece properties, such as a high one Wear resistance or sufficient corrosion resistance, metallic workpieces are subjected to a thermochemical heat treatment. The result of the heat treatment is about nitriding or nitrocarburizing Enriching the edge layer of the workpieces with nitrogen and / or Carbon in order to achieve the required mechanical and to impart chemical properties on the surface and in the edge area.
Beim Nitrieren, zum Beispiel in einer ammoniakhaltigen Gasatmosphäre, erfolgt die Anreicherung der Randschicht mit Stickstoff dadurch, dass der in einem Reaktionsgas enthaltene Ammoniak (NH3) bei Temperaturen von in der Regel über 500 °C unter der katalytischen Wirkung der Oberfläche der zu nitrierenden Werkstücke in Stickstoff (N) und Wasserstoff (H) zerfällt. Hierbei wird an der Werkstückoberfläche das Ammoniakmolekül adsorbiert und stufenweise abgebaut, wodurch der benötigte Stickstoff in atomarer Form freigesetzt wird und zur Lösung im Eisen sowie zur Bildung von Eisennitrid (FexN) zur Verfügung steht. Beim Nitrocarburieren findet darüber hinaus eine gleichzeitige Anreicherung der Randschicht mit Kohlenstoff statt. Atomarer Kohlenstoff (C) diffundiert dabei in analoger Weise durch die Werkstückoberfläche in die Randschicht ein.In nitriding, for example in an ammonia-containing gas atmosphere, the surface layer is enriched with nitrogen by the ammonia (NH 3 ) contained in a reaction gas at temperatures of generally over 500 ° C under the catalytic effect of the surface of the workpieces to be nitrided decays into nitrogen (N) and hydrogen (H). Here, the ammonia molecule is adsorbed and gradually degraded on the workpiece surface, whereby the required nitrogen is released in atomic form and is available for solution in iron and for the formation of iron nitride (Fe x N). When nitrocarburizing, the surface layer is simultaneously enriched with carbon. Atomic carbon (C) diffuses in an analogous manner through the workpiece surface into the surface layer.
Von besonderer Bedeutung hinsichtlich der geforderten Eigenschaften der behandelten Werkstücke ist der im Allgemeinen zwischen 1 µm und 30 µm dicke äußerste Randschichtbereich, die sogenannte Verbindungsschicht, die beim Nitrieren oder Nitrocarburieren vorwiegend aus hexagonalem ε-Nitrid (Fe2-3N) und kubisch-flächenzentriertem γ'-Nitrid (Fe4N) besteht. Die Wahl der Prozessparameter Temperatur und Behandlungsdauer, jedoch vor allem die Zusammensetzung des verwendeten Reaktionsgases haben entscheidenden Einfluss auf die Eigenschaften der Verbindungsschicht. Dies ist darauf zurückzuführen, dass der Anteil der durch die Oberfläche in die Randschicht diffundierenden Elemente, etwa Stickstoff (N), Kohlenstoff (C) oder auch Sauerstoff (O) und Schwefel (S), bei gegebenen Prozessparametem Temperatur und Behandlungsdauer durch die Reaktionsgaszusammensetzung bestimmt wird.Of particular importance with regard to the required properties of the treated workpieces is the outermost surface area, generally between 1 µm and 30 µm thick, the so-called connection layer, which, when nitriding or nitrocarburizing, mainly consists of hexagonal ε-nitride (Fe 2-3 N) and face-centered cubic γ'-nitride (Fe 4 N). The choice of the process parameters temperature and duration of treatment, but above all the composition of the reaction gas used, have a decisive influence on the properties of the connection layer. This is due to the fact that the proportion of the elements diffusing through the surface into the surface layer, such as nitrogen (N), carbon (C) or also oxygen (O) and sulfur (S), determines the temperature and treatment duration by the reaction gas composition for a given process parameter becomes.
Die durch den Quotienten des Partialdrucks von Ammoniak (pNH3) und der 1.5-fachen Potenz des Partialdrucks von Wasserstoff (pH2 3/2) gebildete Nitrierkennzahl KN = pNH3 / pH2 3/2 und die zum Beispiel durch den Quotienten des Quadrats des Partialdrucks von Kohlenmonooxid (pCO 2) und des Partialdrucks von Kohlendioxid (pCO2) gebildete Kohlungskennzahl KC = pCO 2 / pCO2 oder alternativ durch den Quotienten des Partialdrucks von Methan (pCH4) und des Quadrats des Partialdrucks von Wasserstoff (pH2 2) gebildete Kohlungskennzahl KC = pCH4 / pH2 2 des Reaktionsgases geben Aufschluss über den in der Verbindungsschicht maßgeblich in Abhängigkeit von den Prozessparametem Temperatur und Behandlungsdauer sowie der Reaktionsgaszusammensetzung hervorgerufenen Gehalt an Stickstoff bzw. Kohlenstoff. So beläuft sich die Kohlungskennzahl KC bei einem im Hinblick auf einen optimierten Gehalt an ε-Nitrid üblicherweise zum Nitrocarburieren eingesetzten Reaktionsgas mit einer Zusammensetzung aus 50 Vol.-% Ammoniak (NH3) und 50 Vol.-% Endogas auf Werte zwischen 1,5 und 2,5, wenn sich der Anteil an während des Nitrocarburierens umgesetztem Ammoniak in der Gasatmosphäre zwischen 15 Vol.-% und 40 Vol.-% bewegt. Bedeutend niedriger ist hingegen die Kohlungskennzahl KC bei einem Reaktionsgas mit einer Zusammensetzung aus 50 Vol.-% NH3, 45 Vol.-% N2 und 5 Vol.-% CO2. The nitriding index K N = p NH3 / p H2 3/2 formed by the quotient of the partial pressure of ammonia (p NH3 ) and the 1.5-fold power of the partial pressure of hydrogen (p H2 3/2 ) and that, for example, by the quotient of carburizing K C = formed square of the partial pressure of carbon monoxide (P CO 2) and the partial pressure of carbon dioxide (p CO2) p CO 2 / p CO2 or, alternatively, by the quotient of the partial pressure of methane (P CH4) and the square of the partial pressure of hydrogen (p H2 2 ) The carbonization index K C = p CH4 / p H2 2 of the reaction gas provides information about the nitrogen or carbon content in the connection layer, which is largely dependent on the process parameters, temperature and treatment duration and the reaction gas composition. For example, the carbon index K C for a reaction gas with a composition of 50% by volume ammonia (NH 3 ) and 50% by volume endogas, which is usually used for nitrocarburizing with regard to an optimized content of ε-nitride, has values between 1, 5 and 2.5, if the proportion of ammonia reacted during nitrocarburizing in the gas atmosphere is between 15% by volume and 40% by volume. In contrast, the carbonization index K C is significantly lower for a reaction gas with a composition of 50% by volume NH 3 , 45% by volume N 2 and 5% by volume CO 2 .
Wird das Nitrocarburieren mit einem Anteil an Kohlendioxid in der Gasatmosphäre
zwischen 0 Vol.-% und 7 Vol.-% und einem Anteil an Ammoniak zwischen 0 Vol.-%
und 40 Vol.-% durchgeführt, so nimmt die Kohlungskennzahl KC Werte zwischen
0 und 0,5 an. Aufgrund des durch die Formel:
Dies hat zur Folge, dass die Kohlungskennzahl KC bei vorgegebener Nitrierkennzahl KN nur im beschränkten Maße veränderlich und insofern nur begrenzt zur Beeinflussung von Werkstückeigenschaften nutzbar ist. Nachteilig ist femer, dass die Kohlungskennzahl KC bei den gewöhnlich eingesetzten Reaktionsgasen nicht ausreichend hohe Werte aufweist, so dass die durch den Gehalt an Kohlenstoff in der Verbindungsschicht beeinflussten technischen Eigenschaften von metallischen Werkstücken, wie etwa die Verschleißfestigkeit oder die Korrosionsbeständigkeit, nicht im möglichen Umfang ausgenutzt werden können.The consequence of this is that the carbonization index K C can only be changed to a limited extent with a predetermined nitriding index K N and can therefore only be used to a limited extent to influence workpiece properties. A disadvantage is furthermore that the carburizing K C in the commonly used reaction gases has not sufficiently high values such that the influenced by the content of carbon in the bonding layer technical properties of metallic workpieces, such as wear resistance or corrosion resistance, not to the extent possible can be exploited.
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Wärmebehandlung metallischer Werkstücke dahingehend weiterzubilden, dass sich ein verbesserter Verschleiß- und Korrosionswiderstand der behandelten Werkstücke erzielen lässt.The invention is based on the object of developing a method for the heat treatment of metallic workpieces in such a way that an improved wear and corrosion resistance of the treated workpieces can be achieved.
Diese Aufgabe wird durch ein Verfahren gemäß Anspruch 1 und durch die Verwendung einer Vorrichtung gemäß Anspruch 6 gelöst. Ein solches Verfahren macht sich die überraschende Erkenntnis zu eigen, dass die bislang verfahrensbedingte Koppelung der Kohlungskennzahl KC an die Nitrierkennzahl KN durch das aufgrund der Zugabe von Kohlenwasserstoffen in das Reaktionsgas bewirkte zusätzliche Kohlenstoffangebot in der Gasatmosphäre aufgehoben wird. Durch die Zugabe von Kohlenwasserstoffen als Kohlenstoffspender lässt sich danach die Kohlungskennzahl KC unabhängig von der Nitrierkennzahl KN verändern. Dies hat zur Folge, dass sich vergleichsweise hohe Werte für die Kohlungskennzahl KC in der Gasatmosphäre erreichen lassen. Indem der Kohlenstoff- und Stickstoffgehalt in der Verbindungsschicht verfahrensgemäß durch die Vorgabe der Kohlungskennzahl KC und der Nitrierkennzahl KN gezielt eingestellt werden, ist daher ein verhältnismäßig hoher Gehalt an Kohlenstoff in der Verbindungsschicht, der den Verschleiß- und Korrosionswiderstand signifikant verbessert, sichergestellt.This object is achieved by a method according to claim 1 and by the use of a device according to claim 6. Such a process embraces the surprising finding that the process-related coupling of the coaling index K C to the nitriding index K N has been eliminated by the additional carbon supply in the gas atmosphere caused by the addition of hydrocarbons in the reaction gas. By adding hydrocarbons as carbon donors, the carbon index K C can then be changed independently of the nitriding index K N. This has that can be comparatively achieve high values for carburizing K C in the gas atmosphere result. By the carbon and nitrogen content to be moved in accordance with selectively adjusted in the connecting layer by specifying the carburizing K C and the nitriding potential K N, therefore a relatively high content of carbon in the bonding layer, the significantly improved wear and corrosion resistance is ensured.
Als besonderes vorteilhaft hat sich herausgestellt, ungesättigte Kohlenwasserstoffe des Typs CnH2n, vorzugsweise Ethylen (C2H4) oder Propylen (C2H6), zuzusetzen. Von Vorteil ist aber auch, gesättigte Kohlenwasserstoffe des Typs CnH2n+2, vorzugsweise Ethan (C2H6) oder Propan (C3H8), zuzugegeben. Denn durch thermische Spaltung der gesättigten Kohlenwasserstoffe während des Verfahrensablaufs können ungesättigte Kohlenwasserstoffe entstehen.It has turned out to be particularly advantageous to add unsaturated hydrocarbons of the type C n H 2n , preferably ethylene (C 2 H 4 ) or propylene (C 2 H 6 ). However, it is also advantageous to add saturated hydrocarbons of the type C n H 2n + 2 , preferably ethane (C 2 H 6 ) or propane (C 3 H 8 ). This is because thermal splitting of the saturated hydrocarbons during the course of the process can result in the formation of unsaturated hydrocarbons.
Um eine determinierte Kohlungskennzahl KC in der Gasatmosphäre zu gewährleisten, werden die Kohlenwasserstoffe zweckmäßigerweise während der gesamten Wärmebehandlung zugegeben. In alternativer Weiterbildung der Erfindung können die Kohlenwasserstoffe vorteilhafterweise auch nur während des Haltens auf einer bestimmten Temperatur, vorzugsweise einer Nitriertemperatur zwischen 500 °C und 700 °C, zugegeben werden. Im Hinblick auf eine bezüglich der geforderten Werkstückeigenschaften optimierte Verfahrensführung kann es außerdem zweckdienlich sein, die Kohlenwasserstoffe erst zum Ende des Haltens auf Nitriertemperatur zuzugegeben.To a deterministic carburizing K C in the gas atmosphere to ensure the hydrocarbons are conveniently added during the entire heat treatment. In an alternative development of the invention, the hydrocarbons can advantageously also be added only while they are kept at a certain temperature, preferably a nitriding temperature between 500 ° C. and 700 ° C. With regard to a process control optimized with regard to the required workpiece properties, it may also be expedient to add the hydrocarbons only at the end of the holding to the nitriding temperature.
Eine besonders vorteilhafte Verfahrensführung ist ferner dann gegeben, wenn die Kohlenwasserstoffe diskontinuierlich, etwa nur zu bestimmten Zeiten, zugegeben werden, wodurch eine prozessangepasste Verfahrensführung ermöglicht wird. Die erfindung gemäß vorgesehene Begrenzung der Zugabe von Kohlenwasserstoffen je nach Zusammensetzung des Reaktionsgases auf einen Anteil von 3 Vol.% bis 25Vol % bietet den Vorteil, dass eine verstärkte Abscheidung von freiem Kohlenstoff, der im Allgemeinen zu einem unerwünschten Verrußen, beispielsweise des Innenraums von Wärmebehandlungsöfen, führt, vermieden wird. In vorteilhafter Ausgestaltung der Erfindung wird ein Reaktionsgas mit einer Zusammensetzung aus 95 Vol.-% Ammoniak (NH3) und 5 Vol.-% Propan (C3H8) vorgeschlagen, das auch in wirtschaftlicher Hinsicht günstig herzustellen ist.A particularly advantageous procedure is also given when the hydrocarbons are added discontinuously, for example only at certain times, which enables a process-adapted procedure. The invention according to the proposed limitation of the addition of hydrocarbons to a proportion of 3 vol.% To 25 vol.% Depending on the composition of the reaction gas offers the advantage that an increased separation of free carbon, which generally leads to undesired sooting, for example the interior of heat treatment furnaces , leads, is avoided. In an advantageous embodiment of the invention, a reaction gas with a composition of 95% by volume ammonia (NH 3 ) and 5% by volume propane (C 3 H 8 ) is proposed, which can also be produced economically.
Schließlich wird die Verwendung einer Vorrichtung zur Durchführung eines solchen Verfahrens vorgeschlagen, die aus einem Wärmebehandlungsofen mit einem beheizbaren, gasdichten Innenraum zum Nitrocarburieren von metallischen Werkstücken und mit einer Einrichtung zum dosierten Zugeben von Ammoniak und Kohlenwasserstoffen besteht.Finally, the use of a device for performing a proposed such a method using a heat treatment furnace a heatable, gas-tight interior for nitrocarburizing metallic Workpieces and with a device for the metered addition of ammonia and hydrocarbons.
Einzelheiten und weitere Vorteile der Gegenstände der vorliegenden Erfindung ergeben sich aus der nachfolgenden Beschreibung eines bevorzugten Ausführungsbeispieles. In der zugehörigen Zeichnung zeigen im Einzelnen:
- Fig. 1
- ein den Gehalt von Stickstoff und Kohlenstoff in der Verbindungsschicht eines nitrocarburierten Werkstücks in Abhängigkeit vom Randabstand zeigendes Diagramm bei Verwendung eines konventionellen Reaktionsgases und
- Fig. 2
- ein Fig. 1 entsprechendes Diagramm bei Verwendung eines Reaktionsgases, dem ein Kohlenwasserstoff zugegeben ist.
- Fig. 1
- a diagram showing the content of nitrogen and carbon in the connecting layer of a nitrocarburized workpiece as a function of the edge distance when using a conventional reaction gas and
- Fig. 2
- a diagram corresponding to Fig. 1 when using a reaction gas to which a hydrocarbon is added.
In den Fig. 1 und 2 ist der Gehalt an Kohlenstoff wC und Stickstoff wN der Verbindungsschicht zweier nitrocarburierter Werkstückproben in Abhängigkeit vom Randabstand r der Verbindungsschicht dargestellt. Zur vergleichenden Analyse der chemischen Zusammensetzung der Verbindungsschichten wurden die identischen Werkstückproben der Stahlsorte 16 Mn Cr 5 (Werkstoff-Nr. 1.7131) in einer ammoniakhaltigen Gasatmosphäre eines Kammerofens auf eine Nitriertemperatur von ca. 580 °C aufgeheizt. Während sodann die erste Werkstückprobe mit einem konventionellen Reaktionsgas G1, bestehend aus 50 Vol.-% NH3, 45 Vol.-% N2 und 5 Vol.-% CO2, bei einer verhältnismäßig hohen Nitrierkennzahl von KN = 3,1 und einer zugehörigen Kohlungskennzahl von KC = 0,2 (bezogen auf das Verhältnis CO/CO2) behandelt wurde, ist die zweite Werkstückprobe durch ein einen Kohlenwasserstoffzusatz aufweisendes Reaktionsgas G2 mit der Zusammensetzung 95 Vol.-% NH3 und 5 Vol.-% C3H8 bei in etwa gleicher Nitrierkennzahl von KN = 3,3, aber höherer Kohlungskennzahl von KC = 0,45 (bezogen auf das Verhältnis CH4/H2) nitrocarburiert worden. Der den Kammerofen dabei durchströmende Volumenstrom der Reaktionsgase G1, G2 betrug jeweils ca. 4 m3/h. Nach ca. 180 min Nitrocarburierdauer wurden die Proben in einer Stickstoffatmosphäre auf Raumtemperatur abgekühlt. Die im Anschluss bestimmte Verbindungsschicht betrug jeweils ca. 16 µm - 18 µm.1 and 2 show the content of carbon w C and nitrogen w N of the connecting layer of two nitrocarburized workpiece samples as a function of the edge distance r of the connecting layer. For a comparative analysis of the chemical composition of the connecting layers, the identical workpiece samples of the steel grade 16 Mn Cr 5 (material no. 1.7131) were heated to a nitriding temperature of approx. 580 ° C in an ammonia-containing gas atmosphere of a chamber furnace. Then the first workpiece sample with a conventional reaction gas G 1 , consisting of 50 vol.% NH 3 , 45 vol.% N 2 and 5 vol.% CO 2 , with a relatively high nitriding index of K N = 3.1 and an associated carbon index of K C = 0.2 (based on the CO / CO 2 ratio), the second workpiece sample is treated with a hydrocarbon additive containing reaction gas G 2 with the composition 95 vol.% NH 3 and 5 vol. -% C 3 H 8 with approximately the same nitriding index of K N = 3.3, but a higher carbon index of K C = 0.45 (based on the ratio CH 4 / H 2 ) was nitrocarburized. The volume flow of reaction gases G 1 , G 2 flowing through the chamber furnace was in each case approximately 4 m 3 / h. After approximately 180 minutes of nitrocarburizing, the samples were cooled to room temperature in a nitrogen atmosphere. The connection layer determined afterwards was approx. 16 µm - 18 µm.
Der Vergleich der in den Fig. 1 und 2 gezeigten Elemententiefenprofile zeigt, dass der Stickstoffgehalt in beiden Fällen in die Tiefe allmählich und nahezu übereinstimmend abnimmt. Lediglich in einem Bereich nahe der Oberfläche ist der Stickstoffgehalt bei der mit dem Reaktionsgas G1 behandelten Werkstückprobe etwas höher.The comparison of the element depth profiles shown in FIGS. 1 and 2 shows that the nitrogen content in both cases gradually and almost coincidentally decreases in depth. Only in an area near the surface is the nitrogen content somewhat higher in the workpiece sample treated with the reaction gas G 1 .
Dagegen unterscheiden sich die Tiefenprofile von Kohlenstoff beträchtlich voneinander. Die Kurve des Kohlenstoffgehalts bei der mit dem Reaktionsgas G2 behandelten Werkstückprobe liegt bis über die Mitte der Verbindungsschicht erheblich über dem mit dem Reaktionsgas G1 erzielten Kohlenstoffgehalt und nimmt erst dann einen in etwa mit diesem übereinstimmenden und zum Abfall des Stickstoffgehalts ungefähr parallelen Verlauf ein. Der Verlauf des Gehalts an Kohlenstoff in den Fig. 1 und 2 bestätigt somit, dass durch den Propanzusatz im Reaktionsgas G2 ein höherer Kohlenstoffgehalt in der Verbindungsschicht erzeugt wird, der von einer höheren Kohlungskennzahl KC des Reaktionsgases G2 herrührt und nicht zuletzt zu einem verbesserten Verschleiß- und Korrosionswiderstand der Werkstückprobe führt. In contrast, the depth profiles of carbon differ considerably from one another. The curve of the carbon content in the workpiece sample treated with the reaction gas G 2 lies considerably above the carbon content achieved with the reaction gas G 1 up to the middle of the connecting layer and only then takes a course that roughly matches this and is approximately parallel to the drop in the nitrogen content. The course of the carbon content in FIGS. 1 and 2 thus confirms that the addition of propane in the reaction gas G 2 produces a higher carbon content in the connecting layer, which results from a higher carbon index K C of the reaction gas G 2 and not least to one leads to improved wear and corrosion resistance of the workpiece sample.
- wC w C
- KohlenstoffgehaltCarbon content
- wN w N
- Stickstoffgehaltnitrogen content
- rr
- Randabstandmargin
- G1 G 1
- Reaktionsgasreaction gas
- G2 G 2
- Reaktionsgasreaction gas
Claims (6)
- Method of nitrocarburising iron materials in a gas atmosphere which contains nitrogen, in which the nitrogen and carbon content available in the connecting layer of the case of the treated workpieces is intentionally adjusted by appropriate selection of the nitride coefficient KN and carburising coefficient KC of a reaction gas containing ammonia, characterised in that hydrocarbons are additionally added to the reaction gas during the entire heat treatment or while a nitriding temperature between 500°C and 700°C is maintained in order to produce a nitrocarburising atmosphere with a proportion of 3% to 25% by volume of hydrocarbons and the link between the carburising coefficient KC and the nitride coefficient KN is eliminated during the treatment.
- Method as claimed in Claim 1, characterised in that unsaturated hydrocarbons of the CnH2n type, preferably ethylene (C2H4) or propylene (C2H6), or unsaturated hydrocarbons of the CnH2n+2, preferably ethane (C2H6) or propane (C3H8), are added.
- Method as claimed in either Claim 1 or Claim 2, characterised in that the hydrocarbons are not added until the end of the period during which the nitriding temperature is maintained.
- Method as claimed in any one of Claims 1 to 3, characterised in that the hydrocarbons are added discontinuously.
- Method as claimed in any one of the preceding claims, characterised by a reaction gas with a composition of 95% by volume ammonia (NH3) and 5% by volume propane (C3H8).
- Use of an apparatus for carrying out the method as claimed in any one of the preceding claims, comprising a heat treatment furnace with a heatable, gas-tight interior for nitrocarburising metal workpieces and with an arrangement for metered addition of ammonia and hydrocarbons.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP20000102360 EP1122330B1 (en) | 2000-02-04 | 2000-02-04 | Process and use of an apparatus for nitrocarburizing of metallic parts |
| AT00102360T ATE280847T1 (en) | 2000-02-04 | 2000-02-04 | METHOD AND USE OF A DEVICE FOR NITROCARBURIZING IRON MATERIALS |
| DE50008409T DE50008409D1 (en) | 2000-02-04 | 2000-02-04 | Method and use of a device for nitrocarburizing ferrous materials |
| US09/562,698 US6406560B1 (en) | 2000-02-04 | 2000-04-28 | Method for the thermal treatment of metal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP20000102360 EP1122330B1 (en) | 2000-02-04 | 2000-02-04 | Process and use of an apparatus for nitrocarburizing of metallic parts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1122330A1 EP1122330A1 (en) | 2001-08-08 |
| EP1122330B1 true EP1122330B1 (en) | 2004-10-27 |
Family
ID=8167774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP20000102360 Expired - Lifetime EP1122330B1 (en) | 2000-02-04 | 2000-02-04 | Process and use of an apparatus for nitrocarburizing of metallic parts |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US6406560B1 (en) |
| EP (1) | EP1122330B1 (en) |
| AT (1) | ATE280847T1 (en) |
| DE (1) | DE50008409D1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102732820A (en) * | 2011-04-10 | 2012-10-17 | 上海上大热处理有限公司 | Gas nitrocarburizing method for automobile brake disc |
| DE102013226091A1 (en) | 2013-12-16 | 2015-06-18 | Robert Bosch Gmbh | Cylinder drum of a hydrostatic axial piston machine with a wear protection layer |
| DE102013226090A1 (en) | 2013-12-16 | 2015-06-18 | Robert Bosch Gmbh | Process for gas nitrocarburizing |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7622197B2 (en) * | 2006-11-20 | 2009-11-24 | Ferroxy-Aled, Llc | Seasoned ferrous cookware |
| DE102009038598B4 (en) * | 2009-08-26 | 2017-06-22 | Ipsen International Gmbh | Process and device for the treatment of process gases for heat treatment of metallic materials / workpieces in industrial furnaces |
| EP2739877B1 (en) * | 2011-06-30 | 2015-08-19 | Robert Bosch GmbH | Flexible ring for a drive belt for a continuously variable transmission and method for producing such |
| US9389155B1 (en) * | 2013-03-12 | 2016-07-12 | United Technologies Corporation | Fatigue test specimen |
| WO2019205114A1 (en) * | 2018-04-28 | 2019-10-31 | 邢台三厦铸铁有限公司 | Cast iron cookware and method for treating surface thereof |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4496401A (en) * | 1981-10-15 | 1985-01-29 | Lucas Industries | Corrosion resistant steel components and method of manufacture thereof |
| FR2524006B1 (en) * | 1982-03-23 | 1985-10-11 | Air Liquide | PROCESS FOR THE SURFACE CURING OF METAL PARTS |
| US4547228A (en) * | 1983-05-26 | 1985-10-15 | Procedyne Corp. | Surface treatment of metals |
| DE3718240C1 (en) * | 1987-05-30 | 1988-01-14 | Ewald Schwing | Process for the heat treatment of metallic workpieces in a gas-flowed fluidized bed |
| DE3937699A1 (en) * | 1989-11-13 | 1991-05-16 | Thaelmann Schwermaschbau Veb | Producing epsilon carbonitride coatings on ferrous components - by controlling gas mixt. compsn. with respect to nitriding and carburising indices required to produce predetermined coating compsn. |
| DD297053A5 (en) * | 1990-08-23 | 1992-01-02 | Zi Fuer Festkoerperphysik Und Werkstofforschung Der Adw,De | WEAR-RESISTANT EPSILON IRON CARBINITRIDE LAYER ON CARBON STEEL STEELS AND METHOD FOR THE PRODUCTION THEREOF |
| DE4033706A1 (en) * | 1990-10-24 | 1991-02-21 | Hans Prof Dr Ing Berns | Raising corrosion resistance of surface layer of stainless steel - with low carbon content by diffusion of nitrogen, useful for treatment of tools for food |
| RU2048601C1 (en) * | 1993-12-20 | 1995-11-20 | Рыжов Николай Михайлович | Method and apparatus to diagnose process of steels and alloys chemical thermal treatment in glow discharge |
| DE19509614A1 (en) * | 1995-03-21 | 1996-09-26 | Hans Ruediger Dr Ing Hoffmann | Controlling nitriding value of nitriding and nitrocarburisation atmos |
| DE19719225C1 (en) * | 1997-05-07 | 1998-08-06 | Volker Dipl Ing Leverkus | Method and apparatus for controlling a nitriding or nitro-carburising atmosphere |
-
2000
- 2000-02-04 AT AT00102360T patent/ATE280847T1/en active
- 2000-02-04 DE DE50008409T patent/DE50008409D1/en not_active Expired - Lifetime
- 2000-02-04 EP EP20000102360 patent/EP1122330B1/en not_active Expired - Lifetime
- 2000-04-28 US US09/562,698 patent/US6406560B1/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102732820A (en) * | 2011-04-10 | 2012-10-17 | 上海上大热处理有限公司 | Gas nitrocarburizing method for automobile brake disc |
| CN102732820B (en) * | 2011-04-10 | 2015-01-21 | 上海上大热处理有限公司 | Gas nitrocarburizing method for automobile brake disc |
| DE102013226091A1 (en) | 2013-12-16 | 2015-06-18 | Robert Bosch Gmbh | Cylinder drum of a hydrostatic axial piston machine with a wear protection layer |
| DE102013226090A1 (en) | 2013-12-16 | 2015-06-18 | Robert Bosch Gmbh | Process for gas nitrocarburizing |
| US9970093B2 (en) | 2013-12-16 | 2018-05-15 | Robert Bosch Gmbh | Method for gas carbonitriding |
| US10281042B2 (en) | 2013-12-16 | 2019-05-07 | Robert Bosch Gmbh | Cylinder drum of a hydrostatic axial piston machine having a wear-resistant layer |
Also Published As
| Publication number | Publication date |
|---|---|
| DE50008409D1 (en) | 2004-12-02 |
| EP1122330A1 (en) | 2001-08-08 |
| ATE280847T1 (en) | 2004-11-15 |
| US6406560B1 (en) | 2002-06-18 |
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