EP0132602A1 - Salt bath for the currentless production of wear-resistant boride layers - Google Patents
Salt bath for the currentless production of wear-resistant boride layers Download PDFInfo
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- EP0132602A1 EP0132602A1 EP84107296A EP84107296A EP0132602A1 EP 0132602 A1 EP0132602 A1 EP 0132602A1 EP 84107296 A EP84107296 A EP 84107296A EP 84107296 A EP84107296 A EP 84107296A EP 0132602 A1 EP0132602 A1 EP 0132602A1
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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
- C23C8/40—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 liquids, e.g. salt baths, liquid suspensions
Definitions
- the invention relates to a salt bath based on alkali and / or alkaline earth metal halides for the currentless production of wear-resistant boride layers on metallic materials at 650 to 1100 ° C. It is used in particular for the production of single-phase, hard and adhesive boride layers on steels to increase wear resistance and improve corrosion resistance.
- Boronizing for wear protection of steel and refractory metals has been a well-known process. Diffusion of the element boron into the surface of the treated workpiece and reaction with the base material results in dense, uniform layers of the respective boride, on iron, for example, the borides FeB Fe 2 B.
- the borides have significantly changed properties compared to the pure metals, in particular most are Borides are very hard, corrosion-resistant and therefore extremely wear-resistant.
- the boride layers are firmly connected to the base material by diffusion.
- borated steels for example, are partly superior to steels treated by nitriding or carburizing. A large number of technical process variants have therefore been developed in the past according to which boride layers, in particular on steel, can be produced.
- boriding in solid boriding agents is used almost exclusively.
- the parts to be treated are packed in iron boxes in a boron-releasing powder, usually mixtures of boron carbide, aluminum oxide, silicon oxide and the like, with activating additives such as ammonium fluoride or potassium borofluoride (e.g. DE-PS 1,796,216).
- activating additives such as ammonium fluoride or potassium borofluoride (e.g. DE-PS 1,796,216).
- the boxes are tightly sealed and annealed for a while, the desired boride layers being formed in direct solid-to-solid reactions or by transporting the boron over the gas phase.
- paste processes are only modifications of powder boriding and have the additional disadvantage that large amounts of stubborn residues have to be dissolved from the parts after the treatment and that even application of the paste is extremely difficult, particularly in the case of parts of complex shape.
- Electroless borating salt baths which contain boric acid and fluoborates in addition to boron carbide (GB-PS 959533) or an alkali or alkaline earth metal halide and fluoborate (U.S. Patent 3,634,145).
- these salt baths have also not been able to establish themselves in practice.
- the salt bath contains boron monofluoride or compounds from which boron monofluoride is formed as an intermediate under bath conditions.
- the boron monofluoride which acts as a borating agent can be added to the melt from the outside or can advantageously be generated in the melt itself.
- the gaseous boron monofluoride produced in a known manner by heating boron trifluoride with finely divided boron is introduced into the salt melt during the boronization process.
- Electroless boronation baths that are particularly easy to operate are obtained when the boron monofluoride is generated in the molten salt itself.
- the required trifluoroboroxol (BOF) 3 is also generated in the melt itself. This is based on the knowledge that (BOF) 3 can be produced very well in an inert melt from alkali / alkaline earth chlorides by reacting boron oxide or borates with alkali / alkaline earth fluorides, the presence of barium ions in particular having a positive influence.
- the trifluoroboroxol that is produced in this way in a very slow reaction and in a concentration that is barely measurable converts with the boron carbide suspended in the melt to form the boronizing agent, the boron monofluoride BF.
- molten salts which, in addition to alkali and / or alkaline earth halides, contain 1 to 30% by weight of a boron-oxygen compound, 1 to 30% by weight of alkali and / or alkaline earth fluorides and 1 to 15% by weight of boron carbide.
- the trifluoroboroxol formed by reacting boron-oxygen compounds with fluorides brings about a slow, controlled digestion of the boron carbide, wherein boron-active boron monofluoride is released, which boron can release on the workpiece surface through decay.
- boron carbide instead of boron carbide, other known borating agents, such as amorphous boron or calcium boride, can also be used.
- the boriding effect of the melts can be influenced above all by variations in the concentration of boron oxide or borate and in alkali metal / alkaline earth metal fluoride, as well as by changing the temperature and - to a small extent - by changing the concentration of the boron carbide. It has been shown that the inventive Salt melting is possible to produce layers of Fe 2 B on steel without the undesirable boron-rich phase FeB occurring.
- Salt melts which are composed of 30-60% by weight BaCl2, 10-20% by weight B 2 0 3 , alkali and / or alkaline earth borates, 10-30% by weight NaF, 10-25% by weight N aCl and 1-15% by weight are preferably used.
- B 4 C exist.
- Salt melts with 40-55% by weight BaCl, 5-15% by weight B 203 , alkali and / or alkaline earth borate, 18-25% by weight NaF, 15-20% by weight NaCl and 4-10% by weight B are particularly advantageous 4 C.
- the molten salts according to the invention enable one. extremely simple work in practice.
- the salt mixture is melted in a melting crucible made of heat-resistant steel and the B 4 C is kept in suspension by introducing an inert gas stream, for example nitrogen.
- the workpieces to be borated are attached to a charging frame, preheated to 350 C with hot air, for example, and then hung in the melt.
- Steels produce uniform, very wear-resistant, single-phase layers of Fe 2 B, whereby the layer thickness can be varied depending on the base material and the duration of treatment.
- the parts are removed from the melt and quenched, for example in a quenching bath made of sodium and potassium nitrate, which is customary in hardening technology, and then rinsed with water. In this way, no fluoride gets into the waste water.
- the method according to the invention can thus be easily integrated into the existing infrastructure of a salt bath hardening plant without significant investments or additional wastewater treatment being required.
- the method of operation largely corresponds to that of salt bath coal or Salt bath nitriding.
- the melts are composed of relatively cheap components.
- a boriding process is thus available which can compete with the known large-scale processes of salt bath nitriding and salt bath coaling in terms of operation and costs.
- 100 kg of a salt mixture of 50 kg BaCl 2 , 15 kg NaF, 20 kg NaCl, 5 kg B 2 O 3 and 10 kg B 4 C powder are melted in a crucible furnace of size 30/80 and the boron carbide is suspended by introducing a stream of inert gas .
- a treatment temperature of 900 ° C. an FeB-free boride layer of Fe 2 B of 60 ⁇ m thickness is obtained on CK 15 steel with a treatment time of 2 hours.
- 100 kg of a salt mixture of 50 kg BaCl 2 , 25 kg KF, 15 kg NaCl, 5 kg B 2 0 3 and 5 kg B 4 C powder are melted in a crucible furnace of size 30/80 and the boron carbide is introduced by introducing an inert gas stream, eg nitrogen, kept in suspension.
- an inert gas stream eg nitrogen
- an FeB-free Fe 2 B boride layer of 30 ⁇ m thick is obtained on CK-15 steel.
- Particularly good boride layers provide molten salts with the following composition: 50 kg BaCl 2 , 16 kg NaCl, 10 kg B 2 O 3 , 18 kg NaF and 6 kg B 4 C.
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Abstract
Description
Die Erfindung betrifft ein Salzbad auf der Basis von Alkali- und/oder Erdalkalihalogeniden zur stromlosen Erzeugung verschleißfester Boridschichten auf metallischen Werkstoffen bei 650 bis 1100° C. Es dient insbesondere zur Erzeugung einphasiger, harter und haftfester Boridschichten auf Stählen zur Erhöhung der Verschleißfestigkeit und zur Verbesserung der Korrosionsbeständigkeit.The invention relates to a salt bath based on alkali and / or alkaline earth metal halides for the currentless production of wear-resistant boride layers on metallic materials at 650 to 1100 ° C. It is used in particular for the production of single-phase, hard and adhesive boride layers on steels to increase wear resistance and improve corrosion resistance.
Das Borieren zum Verschleißschutz von Stahl und Refraktärmetallen ist ein schon lange bekanntes Verfahren. Durch Eindiffusion des Elementes Bor in die Oberfläche des behandelten Werkstückes und Reaktion mit dem Grundwerkstoff entstehen dichte, gleichmäßige Schichten des jeweiligen Borides, auf Eisen z.B. die Boride FeB Fe2B. Die Boride besitzen gegenüber den reinen Metallen erheblich veränderte Eigenschaften, insbesondere sind die meisten Boride sehr hart, korrosionsbeständig und damit überaus verschleißfest. Durch Diffusion sind die Boridschichten mit dem Grundwerkstoff fest verbunden. Hinsichtlich ihrer Verschleißfestigkeit sind z.B. borierte Stähle zum Teil den durch Nitrieren oder Aufkohlen behandelten Stählen überlegen. Es wurden deshalb in der Vergangenheit eine Vielzahl technischer Verfahrensvarianten entwickelt, nach denen man Boridschichten, insbesondere auf Stahl, herstellen kann.Boronizing for wear protection of steel and refractory metals has been a well-known process. Diffusion of the element boron into the surface of the treated workpiece and reaction with the base material results in dense, uniform layers of the respective boride, on iron, for example, the borides FeB Fe 2 B. The borides have significantly changed properties compared to the pure metals, in particular most are Borides are very hard, corrosion-resistant and therefore extremely wear-resistant. The boride layers are firmly connected to the base material by diffusion. With regard to their wear resistance, borated steels, for example, are partly superior to steels treated by nitriding or carburizing. A large number of technical process variants have therefore been developed in the past according to which boride layers, in particular on steel, can be produced.
In der Praxis wird fast ausschließlich das Borieren in festen Boriermitteln angewendet. Dabei werden die zu behandelnden Teile in eisernen Kästen in ein borabgebendes Pulver, meist Mischungen aus Borcarbid, Aluminiumoxid, Siliziumoxid und dgl., mit aktivierenden Zusätzen, wie Ammoniumfluorid oder Kaliumborfluorid, eingepackt (z.B. DE-PS 1.796.216). Die Kästen werden dicht verschlossen und eine zeitlang geglüht, wobei in direkten Festkörper-Feststoff-Reaktionen oder durch Transport des Bors über die Gasphase die erwünschten Boridschichten gebildet werden.In practice, boriding in solid boriding agents is used almost exclusively. The parts to be treated are packed in iron boxes in a boron-releasing powder, usually mixtures of boron carbide, aluminum oxide, silicon oxide and the like, with activating additives such as ammonium fluoride or potassium borofluoride (e.g. DE-PS 1,796,216). The boxes are tightly sealed and annealed for a while, the desired boride layers being formed in direct solid-to-solid reactions or by transporting the boron over the gas phase.
Diese Pulververfahren besitzen eine Reihe von Nachteilen.These powder processes have a number of disadvantages.
So müssen alle Teile von Hand einzeln sorgfältig in das Pulver eingesetzt werden. Weiterhin sintern die Pulver beim Glühen stark zusammen, so daß die borierten Teile sehr schlecht herauszunehmen sind und zusätzlich nachgereinigt werden müssen. Gleichzeitig werden große Mengen an Borierpulver benötigt, was den Prozeß außerordentlich verteuert. Schließlich muß man beim Borieren in Pulvern mit ungleichmäßigen Schichten rechnen. Eine Qualitätskontrolle ist durch Begutachtung eines einzelnen Teils nicht möglich, da dieses nicht repräsentativ für die Charge ist, denn die Qualität der Teile hängt im wesentlichen von der Sorgfalt beim Einlegen in das Borierpulver ab. Kleine Teile, Teile mit dünnen Bohrungen, Hinterschneidungen usw. lassen sich im Pulver überhaupt nicht oder nur mit extremem Aufwand borieren.All parts must be carefully inserted into the powder by hand. Furthermore, the powders sinter together strongly during annealing, so that the borated parts are very difficult to remove and additionally have to be cleaned. At the same time, large amounts of boron powder are required, which makes the process extremely expensive. Finally, uneven layers must be expected when boronizing in powders. A quality control is not possible by examining a single part, since this is not representative of the batch, because the quality of the parts essentially depends on the care taken when inserting them into the boron powder. Small parts, parts with thin holes, undercuts etc. cannot be borated in the powder at all or only with extreme effort.
Es hat daher nicht an Versuchen gefehlt, diese Nachteile durch andere Verfahren auszugleichen. So wurde versucht, das Borierpulver in Form einer Aufschlämmung oder Paste auf die Teile zu bringen, das Lösungsmittel zu verdampfen und die Teile in der so entstehenden Kruste aus borierenden Rückständen zu glühen (z.B. H.Kunst, O.Schaaber, Härtereitechn. Mitt. 22 (1967), 275-284).There has been no shortage of attempts to compensate for these disadvantages by other methods. Attempts have been made to apply the boron powder to the parts in the form of a slurry or paste, to evaporate the solvent and to separate the parts Glow crust from boroning residues (e.g. H.Kunst, O.Schaaber, Härtereitechn. Mitt. 22 (1967), 275-284).
Diese als Pastenverfahren bekannten Methoden sind aber nur Modifikationen des Pulverborierens und weisen den zusätzlichen Nachteil auf, daß nach der Behandlung große Mengen hartnäckiger Rückstände von den Teilen auflöst werden müssen und daß ein gleichmäßiges Aufbringen der Paste besonders bei kompliziert geformten Teilen überaus schwierig ist.However, these methods known as paste processes are only modifications of powder boriding and have the additional disadvantage that large amounts of stubborn residues have to be dissolved from the parts after the treatment and that even application of the paste is extremely difficult, particularly in the case of parts of complex shape.
Ebenso schwierig ist es, Blasenbildung beim Pastenauftrag oder Abbröckeln der Kruste beim Glühen zu vermeiden.It is equally difficult to avoid blistering when applying paste or crumbling off when annealing.
Es wurde daher auch versucht, in gasförmigen Medien zu borieren, beispielsweise mit Borhalogenid/Wasserstoffgemischen (EP-OS 76488). Man erhält so zwar Boridschichten, diese sind aber technisch unbrauchbar oder nur auf sehr aufwendige Weise herstellbar. Beim Borieren mit Borhalogeniden tritt immer eine unkontrollierbare Korrosion des Grundwerkstoffs auf, da.dieser mit dem Borhalogenid unter Bildung von Metallhalogenid und Borid reagiert. Dadurch entstehen löchrige, unterfressene Boridschichten. Das Borieren mit Diboran ist technisch wegen der extremen Explosibilität und hohen Giftigkeit dieses Gases nahezu unmöglich. Daneben ist ein Borieren mit den genannten gasförmigen Medien wegen der hohen Preise der Borverbindungen auch unwirtschaftlich.An attempt was therefore also made to borate in gaseous media, for example using boron halide / hydrogen mixtures (EP-OS 76488). Although boride layers are obtained in this way, they are technically unusable or can only be produced in a very complex manner. When boronizing with boron halides, there is always uncontrollable corrosion of the base material, which means that it reacts with the boron halide to form metal halide and boride. This creates perforated, undernourished boride layers. Boronizing with diborane is technically almost impossible due to the extreme explosiveness and high toxicity of this gas. In addition, boronizing with the gaseous media mentioned is also uneconomical because of the high prices of the boron compounds.
Aus diesen Gründen hat man versucht, durch Borieren in flüssigen Medien, besonders in geschmolzenen Salzen, die angeführten Nachteile zu vermeiden. So wurden Schmelzen auf der Basis von Alkali- und Erdalkalichloriden mit B203, Borax oder KBF4 beschrieben. In solchen Schmelzen kann ein Werkstoff jedoch nur dann boriert werden, wenn gleichzeitig eine Elektrolyse durchgeführt wird. Dabei werden die zu borierenden Werkstücke kathodisch geschaltet, der Tiegel oder ein Graphitstab dient als Anode. Diese Verfahren weisen den Nachteil auf, daß unterschiedliche Stromdichten an komplizierten Teilen ungleichmäßige Schichtdicken erzeugen. Außerdem entsteht Sauerstoff, Chlor oder Fluor an der Anode, wodurch starke Korrosion hervorgerufen wird. Weiterhin ist die Chargierung schwierig, da eine elektrische Kontaktierung der einzelnen Teile erforderlich ist. Aus diesen Gründen haben sich elektrolytische Borierverfahren in Salzschmelzen in der Technik nicht einführen lassen.For these reasons, attempts have been made to avoid the disadvantages mentioned by boriding in liquid media, especially in molten salts. For example, melts based on alkali and alkaline earth chlorides with B 2 0 3 , borax or KBF 4 have been described. In such melts, however, a material can only be borated if electrolysis is carried out at the same time. The workpieces to be borated are connected cathodically, the crucible or a graphite rod serves as an anode. These methods have the disadvantage that different current densities produce uneven layer thicknesses on complicated parts. In addition, oxygen, chlorine or fluorine is generated on the anode, which causes severe corrosion. Charging is also difficult because electrical contacting of the individual parts is required. For these reasons, electrolytic boriding processes in molten salts have not been able to be introduced in industry.
Demgegenüber ist über das Borieren in Salzschmelzen ohne Elektrolyse nur sehr wenig bekannt. In den Härtereitechn. Mitt. 17 (1962) 131-140 wird eine Schmelze aus 80 % NaCL, 15 % NaBF4 und 5 % B4C beschrieben, wobei aber gleichzeitig darauf hingewiesen wird, daß das in der Schmelze gelöste NaBF4 sehr rasch zu NaF und BF3 zerfällt, welches entweicht. Durch diese Instabilität der Schmelze läßt sich keine zeitlich konstante Borierwirkung erhalten, die Schmelze wird sehr rasch inaktiv. Die DE-OS 3118585 gibt ein Verfahren zum Borieren in Salzschmelzen ohne Elektrolyse an, bei dem das zur Borierung erforderliche Bor durch Umsetzung von Borax mit Siliziumcarbid freigesetzt wird. Wegen der Oxidation von SiC zu Si02 durch Luftsauerstoff bzw. durch Aufschluß von SiC mit Borat bildet sich in solchen Schmelzen aber sehr bald eine undurchdringliche Silikatdecke an der Badoberfläche aus.On the other hand, very little is known about boriding in molten salts without electrolysis. In the hardening techn. Mitt. 17 (1962) 131-140 describes a melt of 80% NaCL, 15% NaBF 4 and 5% B 4 C, but at the same time it is pointed out that the NaBF 4 dissolved in the melt very quickly becomes NaF and BF 3 decays, which escapes. This instability of the melt means that a boronizing effect which is constant over time cannot be obtained; the melt becomes inactive very quickly. DE-OS 3118585 specifies a process for boronization in molten salts without electrolysis, in which the boron required for the boronization is released by reacting borax with silicon carbide. Because of the oxidation of SiC to Si0 2 by atmospheric oxygen or by digestion of SiC with borate, an impenetrable silicate blanket very quickly forms on the bath surface in such melts.
Weiterhin sind stromlose Boriersalzbäder bekannt, die neben Borcarbid Borsäure und Fluoborate enthalten (GB-PS 959533) bzw. ein Alkali oder Erdalkalihalogenid und Fluoborate (US-PS 3634145). Doch auch diese Salzbäder haben sich in der Praxis nicht durchsetzen können.Electroless borating salt baths are also known which contain boric acid and fluoborates in addition to boron carbide (GB-PS 959533) or an alkali or alkaline earth metal halide and fluoborate (U.S. Patent 3,634,145). However, these salt baths have also not been able to establish themselves in practice.
Es war daher Aufgabe der vorliegenden Erfindung, ein Salzbad auf der Basis von Alkali- und/oder Erdalkalihalogeniden zur stromlosen Erzeugung verschleißfester Boridschichten auf metallischen Werkstoffen bei Temperaturen von 650 bis 1100° C zu entwickeln, das einfach und preisgünstig zu betreiben ist, keine Krusten auf der Badoberfläche bildet und haftfeste Boridschichten liefert, die insbesondere bei Stählen aus einphasigen Fe2B-schichten bestehen.It was therefore an object of the present invention to develop a salt bath based on alkali and / or alkaline earth halides for the electroless generation of wear-resistant boride layers on metallic materials at temperatures of 650 to 1100 ° C., which is simple and inexpensive to operate, without crusts forms the bath surface and provides adherent boride layers that consist of single-phase Fe 2 B layers, particularly in the case of steels.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß das Salzbad Bormonofluorid oder Verbindungen enthält, aus denen unter Badbedingungen Bormonofluorid intermediär entsteht.This object is achieved according to the invention in that the salt bath contains boron monofluoride or compounds from which boron monofluoride is formed as an intermediate under bath conditions.
Das als Boriermittel wirkende Bormonofluorid kann der Schmelze von außen zugesetzt oder vorteilhafterweise in der Schmelze selbst erzeugt werden. Im ersteren Fall leitet man das auf bekannte Weise durch Erhitzen von Bortrifluorid mit feinverteiltem Bor hergestellte gasförmige Bormonofluorid während des Borierungsprozesses in die Salzschmelze ein.The boron monofluoride which acts as a borating agent can be added to the melt from the outside or can advantageously be generated in the melt itself. In the former case, the gaseous boron monofluoride produced in a known manner by heating boron trifluoride with finely divided boron is introduced into the salt melt during the boronization process.
Besonders einfach zu betreibende stromlose Borierungsbäder erhält man, wenn das Bormonofluorid in der Salzschmelze selbst erzeugt wird. Überraschend wurde gefunden, daß man in einer inerten, gut wasserlöslichen und geringviskosen Schmelze aus Alkali- und Erdalkalichloriden borieren kann, wenn darin suspendiertes Boriermittel, wie zum Beispiel Borcarbid-Pulver durch Trifluorboroxol aktiviert und zur Abgabe von Bormonofluorid veranlaßt wird, welches seinerseits an der Bauteiloberfläche zerfällt und auf diese Weise das Bor vom Borcarbid auf das Werkstück überträgt.Electroless boronation baths that are particularly easy to operate are obtained when the boron monofluoride is generated in the molten salt itself. Surprisingly it has been found that one can boriding in an inert, highly water-soluble and handle low melt of alkali and alkaline earth chlorides, when therein, such as boron carbide powder activated suspended boriding agent by T rifluorboroxol and is caused to emit boron monofluoride, which in turn at the Component surface disintegrates and in this way transfers the boron from the boron carbide to the workpiece.
Das erforderliche Trifluorboroxol (BOF)3 wird ebenfalls in der Schmelze selbst erzeugt. Dem liegt die Erkenntnis zugrunde, daß man (BOF)3 durch Umsetzung von Boroxid oder Boraten mit Alkali-/Erdalkalifluoriden sehr gut in einer inerten Schmelze aus Alkali-/ Erdalkalichloriden erzeugen kann, wobei besonders die Anwesenheit von Bariumionen positiven Einfluß ausübt. Das auf diese Weise in sehr langsamer Reaktion und in kaum meßbarer Konzentration entstehende Trifluorboroxol setzt sich mit dem in der Schmelze suspendierten Borcarbid zu dem eigentlich borierenden Agens, dem Bormonofluorid BF um.The required trifluoroboroxol (BOF) 3 is also generated in the melt itself. This is based on the knowledge that (BOF) 3 can be produced very well in an inert melt from alkali / alkaline earth chlorides by reacting boron oxide or borates with alkali / alkaline earth fluorides, the presence of barium ions in particular having a positive influence. The trifluoroboroxol that is produced in this way in a very slow reaction and in a concentration that is barely measurable converts with the boron carbide suspended in the melt to form the boronizing agent, the boron monofluoride BF.
Vorzugsweise verwendet man daher Salzschmelzen, die neben Alkali- und/oder Erdalkalihalogeniden 1 bis 30 Gew % einer Bor-Sauerstoff-Verbindung, 1 bis 30 Gew % Alkali- und/oder Erdalkalifluoride und 1 bis 15 Gew % Borcarbid enthalten.It is therefore preferred to use molten salts which, in addition to alkali and / or alkaline earth halides, contain 1 to 30% by weight of a boron-oxygen compound, 1 to 30% by weight of alkali and / or alkaline earth fluorides and 1 to 15% by weight of boron carbide.
Das durch Umsetzen von Bor-Sauerstoff-Verbindungen mit Fluoriden entstehende Trifluorboroxol bewirkt einen langsamen, kontrollierten Aufschluß des Borcarbids, wobei borieraktives Bormonofluorid freigesetzt wird, das Bor durch Zerfall an der Werkstückoberfläche abgeben kann. Anstelle von Borcarbid können auch andere bekannte Borierungsmittel, wie amorphes Bor oder Kalziumborid, verwendet werden.The trifluoroboroxol formed by reacting boron-oxygen compounds with fluorides brings about a slow, controlled digestion of the boron carbide, wherein boron-active boron monofluoride is released, which boron can release on the workpiece surface through decay. Instead of boron carbide, other known borating agents, such as amorphous boron or calcium boride, can also be used.
Die Borierwirkung der Schmelzen kann vor allem durch Variationen der Konzentration von Boroxid bzw. Borat und von Alkali-/Erdalkalifluorid sowie durch Änderung der Temperatur und - in geringem Maß - durch Änderung der Konzentration des Borcarbids beeinflußt werden. So hat sich gezeigt, daß es mit den erfindungsgemäßen Salzschmelzen möglich ist, auf Stahl Schichten aus Fe2B zu erzeugen, ohne daß die unerwünschte borreiche Phase FeB auftritt.The boriding effect of the melts can be influenced above all by variations in the concentration of boron oxide or borate and in alkali metal / alkaline earth metal fluoride, as well as by changing the temperature and - to a small extent - by changing the concentration of the boron carbide. It has been shown that the inventive Salt melting is possible to produce layers of Fe 2 B on steel without the undesirable boron-rich phase FeB occurring.
Vorzugsweise verwendet man Salzschmelzen, die aus 30-60 Gew % BaCl2, 10-20 Gew % B203, Alkali- und/oder Erdalkaliboraten, 10- 30Gew % NaF, 10-25 Gew % NaCl und 1-15 Gew % B4C bestehen. Besonders vorteilhaft sind Salzschmelzen mit 40-55 Gew % BaCl, 5-15 Gew % B203, Alkali- und/oder Erdalkaliborat, 18-25 Gew.% NaF, 15-20 Gew.% NaCl und 4-10 Gew.% B4C.Salt melts which are composed of 30-60% by weight BaCl2, 10-20% by weight B 2 0 3 , alkali and / or alkaline earth borates, 10-30% by weight NaF, 10-25% by weight N aCl and 1-15% by weight are preferably used. B 4 C exist. Salt melts with 40-55% by weight BaCl, 5-15% by weight B 203 , alkali and / or alkaline earth borate, 18-25% by weight NaF, 15-20% by weight NaCl and 4-10% by weight B are particularly advantageous 4 C.
Die erfindungsgemäßen Salzschmelzen ermöglichen ein . äußerst einfaches Arbeiten in der Praxis. Das Salzgemisch wird in einem Schmelztiegel aus warmfesten Stahl aufgeschmolzen und das B4C durch Einleiten eines Inertgasstromes, z.B. Stickstoff, in Schwebe gehalten. Die zu borierenden Werkstücke werden an einem Chargiergestell befestigt, z.B. mit Heißluft auf 350 C vorgewärmt und danach in die Schmelze eingehängt. Bei Stählen werden gleichmäßige, sehr verschleißfeste, einphasige Schichten von Fe2B erzeugt, wobei die Schichtdicke je nach Grundwerkstoff und Behandlungsdauer variiert werden kann. Die Teile werden der Schmelze entnommen und z.B. in einem in der Härtereitechnik üblichen Abschreckbad aus Natrium- und Kaliumnitrat bei ca. 200°C abgeschreckt und danach mit Wasser gespült. Auf diese Weise gelangt kein Fluorid in die Abwässer.The molten salts according to the invention enable one. extremely simple work in practice. The salt mixture is melted in a melting crucible made of heat-resistant steel and the B 4 C is kept in suspension by introducing an inert gas stream, for example nitrogen. The workpieces to be borated are attached to a charging frame, preheated to 350 C with hot air, for example, and then hung in the melt. Steels produce uniform, very wear-resistant, single-phase layers of Fe 2 B, whereby the layer thickness can be varied depending on the base material and the duration of treatment. The parts are removed from the melt and quenched, for example in a quenching bath made of sodium and potassium nitrate, which is customary in hardening technology, and then rinsed with water. In this way, no fluoride gets into the waste water.
Das erfindungsgemäße Verfahren kann somit problemlos in die bestehende Infrastruktur einer Salzbadhärterei integriert werden, ohne daß nennenswerte Investitionen oder eine zusätzliche Abwasserbehandlung erforderlich sind. Die Arbeitsweise entspricht weitgehend der des Salzbadkohlens oder Salzbadnitrierens. Die Schmelzen sind aus relativ billigen Komponenten zusammengesetzt. Damit ist ein Borierverfahren vorhanden, das hinsichtlich der Arbeitsweise und der Kosten mit den bekannten großtechnischen Verfahren des Salzbadnitrierens und Salzbadkohlens konkurrieren kann.The method according to the invention can thus be easily integrated into the existing infrastructure of a salt bath hardening plant without significant investments or additional wastewater treatment being required. The method of operation largely corresponds to that of salt bath coal or Salt bath nitriding. The melts are composed of relatively cheap components. A boriding process is thus available which can compete with the known large-scale processes of salt bath nitriding and salt bath coaling in terms of operation and costs.
Die folgenden Beispiele geben Salzbadzusammensetzungen zur Durchführung von Borierungen an.The following examples show salt bath compositions for carrying out boronations.
In einem Tiegelofen der Größe 30/80 werden 100 kg eines Salzgemisches aus 50 kg BaCl2, 15 kg NaF, 20 kg NaCl, 5 kg B2O3 und 10 kg B4C-Pulver eingeschmolzen und das Borcarbid durch Einleiten eines Inertgasstromes suspendiert. Bei einer Behandlungstemperatur von 900 °C wird auf CK 15-Stahl bei einer Behandlungsdauer von 2 Stunden eine FeB-freie Boridschicht aus Fe2B von 60 µm Dicke erhalten.100 kg of a salt mixture of 50 kg BaCl 2 , 15 kg NaF, 20 kg NaCl, 5 kg B 2 O 3 and 10 kg B 4 C powder are melted in a crucible furnace of size 30/80 and the boron carbide is suspended by introducing a stream of inert gas . At a treatment temperature of 900 ° C., an FeB-free boride layer of Fe 2 B of 60 μm thickness is obtained on CK 15 steel with a treatment time of 2 hours.
In einem Tiegelofen der Größe 30/80 werden 100 kg eines Salzgemisches aus 50 kg BaCl2, 25 kg KF, 15 kg NaCl, 5 kg B203 und 5 kg B4C-Pulver eingeschmolzen und das Borcarbid durch Einleiten eines Inertgasstromes, z.B. Stickstoff, in Schwebe gehalten.100 kg of a salt mixture of 50 kg BaCl 2 , 25 kg KF, 15 kg NaCl, 5 kg B 2 0 3 and 5 kg B 4 C powder are melted in a crucible furnace of size 30/80 and the boron carbide is introduced by introducing an inert gas stream, eg nitrogen, kept in suspension.
Bei einer Behandlungstemperatur von 850 °C und einer Borierdauer von 2 Stunden wird auf CK-15-Stahl eine FeB-freie Boridschicht aus Fe2B von 30pm Dicke erhalten.At a treatment temperature of 850 ° C. and a boriding time of 2 hours, an FeB-free Fe 2 B boride layer of 30 μm thick is obtained on CK-15 steel.
Besonders gute Boridschichten liefern Salzschmelzen folgender Zusammensetzung: 50 kg BaCl2, 16 kg NaCl, 10 kg B2O3, 18 kg NaF und 6 kg B4C.Particularly good boride layers provide molten salts with the following composition: 50 kg BaCl 2 , 16 kg NaCl, 10 kg B 2 O 3 , 18 kg NaF and 6 kg B 4 C.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT84107296T ATE25267T1 (en) | 1983-07-26 | 1984-06-26 | SALT BATH FOR ELECTRICAL PRODUCTION OF WEAR-RESISTANT BORIDE COATINGS. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3326863 | 1983-07-26 | ||
| DE19833326863 DE3326863A1 (en) | 1983-07-26 | 1983-07-26 | SALT BATH FOR ELECTRICITY-FREE PRODUCTION OF WEAR-RESISTANT BORIDE LAYERS |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0132602A1 true EP0132602A1 (en) | 1985-02-13 |
| EP0132602B1 EP0132602B1 (en) | 1987-01-28 |
Family
ID=6204920
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP84107296A Expired EP0132602B1 (en) | 1983-07-26 | 1984-06-26 | Salt bath for the currentless production of wear-resistant boride layers |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4536224A (en) |
| EP (1) | EP0132602B1 (en) |
| JP (1) | JPS6070169A (en) |
| AT (1) | ATE25267T1 (en) |
| BR (1) | BR8403695A (en) |
| CA (1) | CA1224389A (en) |
| DE (2) | DE3326863A1 (en) |
| ES (1) | ES534584A0 (en) |
| ZA (1) | ZA845139B (en) |
Cited By (1)
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|---|---|---|---|---|
| WO2013011159A1 (en) | 2011-07-15 | 2013-01-24 | Flexngate Automotive Iberica, S.A. | Control pedal for an automotive vehicle |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| EP1587676A4 (en) * | 2002-11-15 | 2010-07-21 | Univ Utah Res Found | Integral titanium boride coatings on titanium surfaces and associated methods |
| US7459105B2 (en) * | 2005-05-10 | 2008-12-02 | University Of Utah Research Foundation | Nanostructured titanium monoboride monolithic material and associated methods |
| US20100176339A1 (en) * | 2009-01-12 | 2010-07-15 | Chandran K S Ravi | Jewelry having titanium boride compounds and methods of making the same |
| US9068260B2 (en) | 2012-03-14 | 2015-06-30 | Andritz Iggesund Tools Inc. | Knife for wood processing and methods for plating and surface treating a knife for wood processing |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU953002A1 (en) * | 1980-11-17 | 1982-08-23 | Институт Электрохимии Уральского Научного-Центра Ан Ссср | Composition for liquid boronizing of products from ferrous metals and alloys |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB959533A (en) * | 1961-10-26 | 1964-06-03 | Gen Motors Corp | Process of boronizing metal or alloy surfaces |
| US3634145A (en) * | 1968-12-09 | 1972-01-11 | Triangle Ind Inc | Case-hardened metals |
| US3936327A (en) * | 1972-09-07 | 1976-02-03 | Elektroschmelzwerk Kempten Gmbh | Boriding composition |
| SU535374A1 (en) * | 1975-01-13 | 1976-11-15 | Воронежский Ордена Ленина Государственный Университет Имени Ленинского Комсомола | Electrolyte for Boronization |
| SU676639A1 (en) * | 1977-06-06 | 1979-07-30 | Предприятие П/Я В-8857 | Composition for liquid borating |
-
1983
- 1983-07-26 DE DE19833326863 patent/DE3326863A1/en not_active Withdrawn
-
1984
- 1984-06-26 DE DE8484107296T patent/DE3462272D1/en not_active Expired
- 1984-06-26 EP EP84107296A patent/EP0132602B1/en not_active Expired
- 1984-06-26 AT AT84107296T patent/ATE25267T1/en not_active IP Right Cessation
- 1984-07-04 ZA ZA845139A patent/ZA845139B/en unknown
- 1984-07-12 US US06/630,302 patent/US4536224A/en not_active Expired - Fee Related
- 1984-07-24 ES ES534584A patent/ES534584A0/en active Granted
- 1984-07-25 CA CA000459631A patent/CA1224389A/en not_active Expired
- 1984-07-25 BR BR8403695A patent/BR8403695A/en unknown
- 1984-07-25 JP JP59153298A patent/JPS6070169A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU953002A1 (en) * | 1980-11-17 | 1982-08-23 | Институт Электрохимии Уральского Научного-Центра Ан Ссср | Composition for liquid boronizing of products from ferrous metals and alloys |
Non-Patent Citations (1)
| Title |
|---|
| HARTEREI-TECHNISCHE MITTEILUNGEN, Band 22 (1967), Rudolf Haufe Verlag 78 Freiburg und 1 Berlin, Seiten 275-284 H. KUNST und O. SCHAABER:"Beobachtungen beim Oberflachenborieren von Stahl", Rudolf Haufe Verlag, 78 Freiburg und 1 Berlin tabellen 1, 3 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013011159A1 (en) | 2011-07-15 | 2013-01-24 | Flexngate Automotive Iberica, S.A. | Control pedal for an automotive vehicle |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0132602B1 (en) | 1987-01-28 |
| US4536224A (en) | 1985-08-20 |
| CA1224389A (en) | 1987-07-21 |
| BR8403695A (en) | 1985-07-09 |
| DE3326863A1 (en) | 1985-02-07 |
| ES8600421A1 (en) | 1985-10-01 |
| DE3462272D1 (en) | 1987-03-05 |
| ES534584A0 (en) | 1985-10-01 |
| ATE25267T1 (en) | 1987-02-15 |
| JPS6070169A (en) | 1985-04-20 |
| ZA845139B (en) | 1985-02-27 |
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