EP0229325B1 - Procédé de fabrication de pièces d'acier résistant à la corrosion - Google Patents

Procédé de fabrication de pièces d'acier résistant à la corrosion Download PDF

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Publication number
EP0229325B1
EP0229325B1 EP86117233A EP86117233A EP0229325B1 EP 0229325 B1 EP0229325 B1 EP 0229325B1 EP 86117233 A EP86117233 A EP 86117233A EP 86117233 A EP86117233 A EP 86117233A EP 0229325 B1 EP0229325 B1 EP 0229325B1
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Prior art keywords
component
oxidising
iron
effected
layer
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EP86117233A
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German (de)
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EP0229325A2 (fr
EP0229325A3 (en
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Cyril Dawes
John David Smith
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ZF International UK Ltd
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Lucas Industries Ltd
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Priority claimed from EP82305400A external-priority patent/EP0077627B1/fr
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • 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
    • C23C8/08—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 only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • 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
    • C23C8/34—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 more than one step
    • 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
    • C23C8/80—After-treatment

Definitions

  • This invention relates to a method of manufacturing a corrosion resistant steel component.
  • the first salt bath heat treatment is effected for about 2 hours at 580°C in a potassium cyanide/potassium cyanate bath.
  • the second heat treatment is effected by quenching the components at 400°C for about 10 minutes in a second salt bath containing sodium hydroxide, potassium hydroxide, and sodium nitrate. This is followed by water quenching of the component. If it is important to restore the oxidized surface of the product to its original finish, it may be necessary to effect a lapping operation at this stage followed by re-treatment in the oxidizing bath for 20 minutes at about 400°C again followed by water quenching.
  • JP-A-48-75433 discloses a method of anti-corrosion surface treatment of steel where the steel is heat treated in a nitriding gaseous atmosphere in a furnace to produce an epsilon iron nitride or carbonitride surface layer thereon, and is then removed from the furnace and held in air whilst still hot for 60 to 120 seconds to produce a 2-3 ⁇ m Fe3O4 layer.
  • the component may be allowed to cool in air or it may be cooled by immersion in oil after the Fe3O4 layer has been formed.
  • GB-A-693715 discloses a process for finishing low carbon steel articles where the articles are heated in a case-hardening furnace to form a hardened surface thereon, quenched, drawn to reduce the surface hardness somewhat, and then tumbled until a polished surface is obtained.
  • a method of manufacturing a corrosion resistant non-alloy steel component comprising the steps of heat treating a non-alloy steel component in a nitriding gaseous atmosphere to produce an epsilon iron nitride or iron carbonitride surface layer thereon; and subsequently oxidising the component to provide an oxide-rich surface layer, characterized in that between the heat treating and oxidising steps the component is cooled and mechanically surface finished.
  • this step is typically effected at a temperature in the range of 550 to 720°C for up to 4 hours in an atmosphere of ammonia, ammonia and endothermic gas, ammonia and exothermic gas or ammonia and nitrogen, with the optional inclusion of at least one or carbon dioxide, carbon monoxide, air, water vapour and methane.
  • ammonia, ammonia and endothermic gas, ammonia and exothermic gas or ammonia and nitrogen with the optional inclusion of at least one or carbon dioxide, carbon monoxide, air, water vapour and methane.
  • exothermic gas and "endothermic gas” are well understood in the art. Carbon dioxide, carbon monoxide, air, water vapour and exothermic gas are oxidising gases.
  • Carbon dioxide, methane and endothermic gas are carburizing gases. It is preferred to effect the heat treatment operation so that the epsilon iron nitride surface layer has a thickness of about 25 micrometres. Thicknesses greater than about 25 micrometre can lead to exfoliation or cracking of the surface layer. Typically, such a layer thickness of about 25 micrometres can be obtained by heat treatment at 660°C for 45 minutes. Such a layer thickness may also be produced by heat treatment of 570°C for 3 hours or at 610°C for 90 minutes. However, the heat treatment temperatures and times may be employed to produce layer thicknesses less than 25 micrometres, e.g. down to 15 micrometres. For example, heat treatment of 570°C for 2 hours can be employed to produce a layer thickness of 16 to 20 micrometres.
  • Components produced by the method of the present invention have a fine surface finish without the need to have a wax protection system to give a good corrosion resistance.
  • the component after being heat treated in the nitriding gaseous atmosphere, is cooled in any desired medium, and then subjected to a lapping or other mechanical surface finishing process to a surface roughness of, for example, not more than 0.2 micrometres R a .
  • This lapping or polishing process will remove any oxide film which may have formed on the component, depending upon the medium used for cooling.
  • the component can then be oxidised at a temperature of 300 to 600°C.
  • the oxidising heat treatment is preferably effected at 350 to 450°C for about 15 to 5 minutes depending upon the temperature in unstripped exothermic gas.
  • the component is preferably heat treated at 500 to 600°C, more preferably, 550 to 600°C followed by quenching to retain nitrogen in solid solution in the ferritic matrix of the steel microstructure.
  • unstripped exothermic gas another type of oxidising atmosphere may be employed such as steam, air or other mixture of oxygen and nitrogen, carbon dioxide and nitrogen, or carbon dioxide alone or any mixture of these gases.
  • Quenching is preferably effected into an oil/water emulsion.
  • an aesthetically pleasing black finish is obtained. Quenching the component directly into an oil/water emulsion without the intermediate oxidation step does not give a black finish but a grey finish where the oxide layer is only 0.1 micrometres thick. However, quenching an already oxidised component into the oil/water emulsion does increase the degree of oxidation to a small extent and thereby darkens the colour.
  • a steel component after having had an epsilon iron nitride surface layer formed thereon by heat treatment at 570°C for about 2 hours in an atmosphere 50% ammonia and 50% endothermic gas mixture is exposed to ambient air for two seconds to effect surface oxidation and then immersed in a bath of an oil-in-water emulsion which, in this embodiment, is produced by mixing a soluble oil sold under the trade mark EVCOQUENCH GW with water in an oil:water volume ratio of 1:6.
  • the resultant product Since the component being quenched is at a temperature greater than 550°C, the resultant product has a good fatigue strength and yield strength in addition to having an aesthetically pleasing black surface with extremely good resistance to corrosion and good bearing properties in view of the absorption of oil into the surface.
  • Components produced in accordance with the invention which have been cooled after exposure to the nitriding atmosphere, polished and then oxidised are more economical to manufacture than hard chromium plating which also suffers from the disadvantage of creating effluent disposal problems. Additionally the gaseous treatment is cheaper than the above-mentioned salt bath treatment, particularly since the latter requires the double oxidising step.
  • Non-alloy steel components produced according to the present invention have a hard wear resistant layer and a surface having an extremely good resistance to humidity and salt spray corrosion. Such components also have a low coefficient of friction (similar to polished hard chromium plating) so that they are capable of being used in sliding applications. Further, such components possess a high surface tension which gives extremely low wettability which is of great help in a resisting humidity and salt spray corrosion attack and also have a pleasing aesthetic appearance (gloss blue/black according to the temperature employed in the oxidising treatment). Additionally, steel components which have been quenched from 550°C to keep nitrogen in solid solution also have good fatigue and yield strength properties.
  • the method of the invention has the advantage that, being of an all gaseous nature, the effluent problems associated with the salt bath heat treatment process are avoided.
  • the method of the invention can be performed by processors with modern gaseous atmosphere heat treatment plant without the requirement for further capital investment in plating or salt bath equipment.
  • the surface layer portion is substantially free of nitrogen atoms.
  • the surface layer portion wherein substantially all of the nitrogen atoms have been displaced by oxygen atoms extends for a depth of at least 0.2, more preferably at least 0.3, micrometre.
  • the resistance of the oxidised surface to corrosion is explained by the predominance of iron oxide, mainly in the form of Fe304 down to a depth of at least 0.1 micrometre and sometimes down to more than 1 micrometre in depth. However, to avoid oxide exfoliation, it is preferred for iron oxide to be present down to a depth not exceeding 1 micrometre.
  • the surface layer portion has a composition approaching that of Fe304 in the part of the surface layer portion immediately under the surface whilst, as the depth increases, the composition has an increasing Fe0 content.
  • a surface layer can be produced by exposing the component having the epsilon iron nitride layer thereon to air before quenching in water/oil emulsion.
  • the part of the surface layer portion immediately below the surface has a composition approaching that of Fe203 but, as the depth increases, the composition becomes progresssively closer to that of Fe304.
  • Such composition can be produced by allowing the component having the epsilon iron nitride layer thereon to cool completely in air Attention is drawn to the disclosure in a Paper entitled “Reappraisal of Nitrocarburising and Nitriding when Applied to Design and Manufacture of Non-alloy Steel Automobile Components" by C. Dawes, D.F. Tranter, and C.G.Smith presented during a symposium entitled “Heat Treatment '79' organised by The Metals Society and American Society for Metals in Birmingham on 22nd to 24th May 1979.
  • Air cooling of the material subsequent to gaseous heat treatment is mentioned in such Paper. However, this is not to be construed as meaning cooling in air, ie an oxidising atmosphere.
  • air cooling was used as a term of art to mean slow cooling and to distinguish the cooling process from oil quenching which is a fast cooling process. In fact, the "air cooling” is more accurately described as "gas cooling” since cooling was effected in the same gaseous nitriding atmosphere used during the heat treatment step to produce the epsilon layer.
  • the oil quenched samples were first vapour degreased and then all the test pieces were introduced into an Auger Electron Spectrometer which was evacuated down to a pressure of 1 x 10 ⁇ 8 torr and allowed to remain under this reduced pressure overnight to remove any gases which had been absorbed into the surface of the samples.
  • the heat treatment process to which the samples were subjected is one which produces an epsilon iron carbonitride layer to a depth well in excess of 20 micrometres.
  • the epsilon iron carbonitride layer consists of a porous and a non-porous region, the porous region extending from the surface of the sample downwardly to a depth of about 10 micrometres, and the non-porous region underlying this At a depth of 20 micrometres, the epsilon iron carbonitride layer has a typical elemental composition of 92% by weight of iron, 7.4% by weight of nitrogen, 0.4% by weight of carbon and 0.2% by weight of oxygen.
  • the elemental composition for the whole layer is consistent with the epsilon iron carbonitride region of the ternary iron-carbon-nitrogen system defined by Naumann and Langescheid (Eisenblinncher 1965, 36,677).
  • the layer of Sample 1 is also consistent with the idealized iron nitride formula Fe2N 1-x where x is 0 to 1, for the epsilon phase reported by Lightfoot and Jack in "Kinetics of Nitriding With and Without White Layer Formation" (Proceedings of Heat Treatment Conference 1973 organised by Heat Treatment and Joint Committee of the Iron and Steel Institute), the nitrogen content being between 7.5 and 11% by weight.
  • Figures 1 to 4 are graphs plotting the iron and nitrogen, iron and oxygen, or iron, oxygen and nitrogen contents in a layer region of Samples 1 to 4 respectively.
  • the layer region chosen is one which extends from 16 x 10 ⁇ 9 metres to about 400 x 10 ⁇ 9 metres from the surface.
  • the first measurement plotted on the graph is that at 16 x 10 ⁇ 9 metres, the samples having been subjected to an initial ion sputtering technique to remove foreign contaminants from the outer surface.
  • oxidation of the Samples after heat treatment either solely in air or initially in air and followed by quenching in the oil/water emulsion results in displacement of nitrogen by oxygen.
  • Displacement of nitrogen is total in the outermost surface layers portions (i.e. down to a depth which may vary between 0.1 micrometre and 1 micrometre,) depending upon the time of exposure to air while the sample is hot before quenching, and also on the cooling rate in the quench. Partial displacement of the nitrogen continues in some instances to depths in excess of 1 micrometre.
  • Samples 2 and 3 were corrosion resistant becauseof the predominance of iron oxide mainly in the form of Fe304 to depth of at least 0.1 micrometre and sometimes down to more than 1 micrometre in depth.
  • the iron to oxygen ratio at the extreme surface indicates a composition approaching that of Fe203 but as the depth increases into the layer, the composition becomes progressively closer to that of Fe304.
  • the iron to oxygen ratio suggests a structure close to Fe304 in the outer surface layer portions but increasing in Fe0 on progression inwards.
  • the first four blocks relate to exposure of nitrocarburised component at above 550°C to air for the specified time, followed by quenching in a water/oil emulsion.
  • the last block relates to quenching of a nitrocarburized component directly into oil without exposure to air.
  • Steel components according to the present invention have a corrosion resistance which is superior even to components surface treated to produce an epsilon iron nitride surface layer, oil quenched, degreased (or slow cooled under a protective atmosphere) and then dipped in a de-watering oil so that the de-watering oil is absorbed into an absorbent outer portion of the epsilon iron nitride surface layer.
  • Table 8 below compares the corrosion resistant properties of various types of steel component:- TABLE 8 SAMPLE NO SALT SPRAY RESISTANCE (HOURS) 1 0 2 17 3 96 4 150+
  • the salt spray resistance was evaluated in a salt spray test in accordance with ATSM Standard B117-64 in which the component is exposed in a salt spray chamber maintained at 95+2-3°F to a salt spray prepared by dissolving 5+/- 1 parts by weight of salt in 95 parts of distilled water and adjusting the pH of the solution such that, when atomised at 95°F, the collect solution has a pH in range of 6.5 to 7.2 After removal from the salt spray test, the components are washed under running water, dried and the incidence of red rusting is assessed. Components exhibiting any red rusting are deemed to have failed.
  • Sample 1 a plain, ie untreated steel component.
  • Sample 2 a steel component having an epsilon iron nitride surface layer produced by the first-mentioned heat treating step in the method of the invention, followed by oil quenching and degreasing (or slow cooling under a protective atmosphere).
  • Sample 3 the steel component of Sample 2 additionally dipped in a de-watering oil.
  • Sample 4 the steel component having an epsilon iron nitride layer and an oxide-rich surface layer produced in accordance with the present invention after lapping the surface to a finish of 0.2 micrometres. It is to be noted that, in the case of Sample 4, the actual salt spray resistance figure depends upon the surface finish.
  • the steel component treated is a shock absorber Piston rod with a final surface finish of 0.13 to 0.15 micrometres Ra.
  • a shock absorber Piston rod with a final surface finish of 0.13 to 0.15 micrometres Ra.
  • Such a component was found to have a salt spray resistance of 250 hours.
  • the improvement in fatigue properties will become apparent from an examination of Table 9 below:- TABLE 9 SAMPLE ENDURANCE LIMIT AT 107 Cycles N/mm2 Plain Notched 5 250 190 6 440 350 7 260 195 8 435 345
  • the fatigue property was evaluated using an NPL-type two point loading rotary beam machine employing standard 0.30" (7.6mm) diameter NPL test pieces.
  • - Sample 5 an untreated steel component.
  • Sample 6 a steel component which has an epsilon iron nitride surface layer formed thereon by heat treatment at 570°C for about 2 hours in an atmosphere of 50% ammonia and 50% endothermic gas mixture, followed by oil quenching.
  • Sample 7 a steel component having an epsilon iron nitride layer produced as in Sample 6 above, and subsequently oxidised in a sodium/potassium hydroxide/sodium nitrate salt bath mixture (sold as "Degussa ABl salt") at a temperature of 400°C as recommended by the suppliers of the salt mixture.
  • Sample 8 a steel component having an epsilon iron nitride surface layer formed by heat treatment as in Sample 6 but subsequently oxidised in steam at 540°C for 30 minutes, followed by oil quenching.
  • a shock absorber piston rod having a length of 230mm, a diameter of 12.5 mm, and an initial surface roughness of 0.13 to 0.15 micrometres Ra was manufactured by machining a bar of low carbon steel (BS970-045M10) and was heat treated for two hours at 570°C in an atmosphere of 50% ammonia and 50% endothermic gas mixture (Carbon monoxide, carbon dioxide, nitrogen and hydrogen). The rod was then cooled slowly under the protection of the same atmosphere as used in the above mentioned heat treatment. The resultant rod had a 20 micrometre thick layer of epsilon iron nitride thereon and a surface roughness of 0.64 micrometres Ra.
  • the rod was oxidised in an exothermic gas mixture containing its moisture of combustion for 10 minutes at 400°C to produce a 0.5 micrometre thick oxide-rich surface layer.
  • the piston rod was then cooled by water quenching.
  • the piston rod was found to have a salt spray resistance of 250 hours according to the above described salt spray test.
  • the rod was oxidised for 15 minutes at 400°C in the exothermic gas mixture, but during the last 5 minutes of the 15 minute cycle, sulphur dioxide was introduced into the furnace in an amount such as to give a concentration of 0.25% by volume in the furnace atmosphere.
  • sulphur dioxide was introduced into the furnace in an amount such as to give a concentration of 0.25% by volume in the furnace atmosphere.
  • Such a technique caused about 1% of the iron oxide (Fe203) on the surface of the rod to be converted to iron sulphide which gave an aesthetically pleasing shiny black surface to the rod.
  • the technique of sulphiding is not restricted to components in the form of damper rods and can be used in respect of any components on which it is desirable to have a black hard-wearing surface. With surface finishes greater than 0.25 micrometres Ra, it will be necessary to wax coat in order to produce the desired corrosion resistance.
  • the S02 content in the oxidizing furnace may be up to 1% by volume and the temperature may be in the range of 300°C to 600°C.
  • the S02 will normally be added to the furnace at some stage after the oxidizing heat treatment has started in order to convert some of the already formed iron oxide to iron sulphide.
  • the invention is particularly applicable to non-alloy steels having a low carbon content, for example up to 0.5% carbon.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Claims (9)

  1. Procédé de fabrication d'un élément en acier non allié résistant à la corrosion, comprenant les étapes de traitement thermique d'un élément en acier non allié dans une atmosphère gazeuse de nitruration pour produire sur celui-ci une couche superficielle d'epsilon nitrure de fer ou de carbonitrure de fer ; et d'oxydation subséquente de l'élément pour fournir une couche superficielle riche en oxyde, caractérisé en ce qu'entre les étapes de traitement thermique et d'oxydation, l'élément est refroidi et sa surface est finie de façon mécanique.
  2. Procédé selon la revendication 1, dans lequel la finition superficielle mécanique est effectuée de sorte que la rugosité superficielle de l'élément ne dépasse pas 0,2 µm Ra.
  3. Procédé selon la revendication 1 ou 2, dans lequel l'oxydation est effectuée en traitant thermiquement l'élément fini en surface dans une atmosphère gazeuse de 300 à 600 °C.
  4. Procédé selon la revendication 3, dans lequel l'élément est une tige de piston.
  5. Procédé selon la revendication 4, dans lequel l'oxydation est effectuée en traitant thermiquement l'élément dans un mélange de gaz exothermique contenant l'humidité de sa combustion.
  6. Procédé selon la revendication 5, dans lequel la couche superficielle riche en oxyde présente une épaisseur de 0,5 µm et est constituée par le Fe3O4.
  7. Procédé selon la revendication 4, dans lequel l'étape de finition superficielle est effectuée de sorte que l'élément, après l'étape d'oxydation, ait une surface de finition de 0,13 à 0,15 µm Ra.
  8. Procédé selon l'une quelconque des revendications 1 à 7, dans lequel le traitement thermique dans l'atmosphère gazeuse de nitruration est effectué à la température de 550 à 720 °C.
  9. Procédé selon l'une quelconque des revendications 1 à 7, dans lequel un composé contenant du soufre est introduit dans l'atmosphère oxydante pour produire du sulfure de fer, de sorte que la surface de l'élément contienne du sulfure de fer ainsi que de l'oxyde de fer.
EP86117233A 1981-10-15 1982-10-11 Procédé de fabrication de pièces d'acier résistant à la corrosion Expired - Lifetime EP0229325B1 (fr)

Applications Claiming Priority (9)

Application Number Priority Date Filing Date Title
GB8131133 1981-10-15
GB8131133 1981-10-15
GB8138318 1981-12-18
GB8138318 1981-12-18
GB8205999 1982-02-26
GB8205999 1982-02-26
GB8220495 1982-07-15
GB8220495 1982-07-15
EP82305400A EP0077627B1 (fr) 1981-10-15 1982-10-11 Pièces en acier résistant à la corrosion et procédé de fabrication

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EP82305400.2 Division 1982-10-11

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EP0229325A2 EP0229325A2 (fr) 1987-07-22
EP0229325A3 EP0229325A3 (en) 1988-09-21
EP0229325B1 true EP0229325B1 (fr) 1995-01-04

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DE10062431A1 (de) * 2000-12-18 2002-06-20 Continental Teves Ag & Co Ohg Hydraulischer Kolben sowie Verfahren zu seiner Oberflächenbehandlung
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JP4762077B2 (ja) * 2006-08-09 2011-08-31 日本パーカライジング株式会社 鉄鋼部材の焼入れ方法、焼入れ鉄鋼部材及び焼入れ表面保護剤
DE102008047724A1 (de) * 2008-09-18 2010-03-25 Schaeffler Kg Gleitscheibe in einer Klemmkörper-Freilaufkupplung
BR112014032480A2 (pt) * 2012-06-26 2017-06-27 Cavina Fulvio Fabrizio processo e instalação para o tratamento antioxidante de superfície de peças de aço
EP4008802A1 (fr) * 2020-12-02 2022-06-08 Linde GmbH Procédé et appareil de post-traitement oxydatif d'un article nitruré ou nitrocarburé

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EP0229325A3 (en) 1988-09-21

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