EP1386018A2 - Method for treating ferrous alloy parts in order to improve the rubbing properties thereof without causing hardness loss or deformation - Google Patents

Method for treating ferrous alloy parts in order to improve the rubbing properties thereof without causing hardness loss or deformation

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Publication number
EP1386018A2
EP1386018A2 EP02727644A EP02727644A EP1386018A2 EP 1386018 A2 EP1386018 A2 EP 1386018A2 EP 02727644 A EP02727644 A EP 02727644A EP 02727644 A EP02727644 A EP 02727644A EP 1386018 A2 EP1386018 A2 EP 1386018A2
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EP
European Patent Office
Prior art keywords
coating
ferrous alloy
fractal dimension
deformation
improve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP02727644A
Other languages
German (de)
French (fr)
Other versions
EP1386018B1 (en
Inventor
Stéphane CHOMER
Jean-Paul Terrat
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hydromecanique et Frottement SAS
Original Assignee
Centre Stephanois de Recherches Mecaniques Hydromecanique et Frottement SA
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Publication of EP1386018A2 publication Critical patent/EP1386018A2/en
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Publication of EP1386018B1 publication Critical patent/EP1386018B1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12951—Fe-base component
    • Y10T428/12958—Next to Fe-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
    • Y10T428/263—Coating layer not in excess of 5 mils thick or equivalent
    • Y10T428/264—Up to 3 mils
    • Y10T428/265—1 mil or less

Definitions

  • the present invention relates to a method of treating ferrous alloy parts to improve their friction properties, mainly their resistance to seizing and sticking, without the risk of losing their hardness or deformation.
  • the invention applies to steel or cast iron parts with high mechanical characteristics, that is to say, whose tempering temperature is less than 200 ° C.
  • lubricants consists in separating the surfaces in contact with a film which promotes sliding and the elimination of calories.
  • the film of lubricant prevents the appearance of micro-welds responsible for seizing and transfer of material.
  • the lubricant film must have a thickness greater than the height of the surface roughness. The thickness of the film largely depends on the surface physicochemical properties and the morphology of the surfaces on a microscopic scale.
  • the machined raw steel has surface characteristics such that the thickness of the lubricant films is generally insufficient to ensure continuous lubrication when the loads or speeds become high.
  • the physicochemical properties of compounds such as iron phosphate or iron sulfide are responsible for the better wetting of lubricants, the surface energy of these constituents being much greater than that of steel. These constituents also have a low shear strength as well as an excellent ability to accommodate, which allows them to improve the running-in conditions and the wear resistance of the contacts subjected to surface fatigue.
  • Electrolytic sulfurization in molten salts in brine is taught in FR-A-1 406 530.
  • Sulfurization at low temperature is carried out in a mixture of molten salts at a temperature around 200 ° C with the assistance of an anodic electrolysis leading to the formation of hexagonal iron sulfide FeS.
  • An object of the invention is to obtain ferrous alloy parts having improved friction properties under extreme conditions of pressure and speed, mainly their resistance to seizing and sticking without loss of their hardness or deformation.
  • the Applicant has surprisingly found that for ferrous alloy parts comprising an iron sulphide coating, the fractal dimension of the surface of the iron sulphide coating plays a role. preponderant, and in any case much more influential than that of stoichiometry, crystal structure or even purity.
  • the Applicant has therefore developed a process for obtaining a piece of ferrous alloy bearing a very high seizing charge with a very low dispersion as well as a high number of cycles, consisting in depositing on said piece a coating of sulphide of iron having an appropriate thickness and Fe / S ratio, characterized in that the coating is selected from those whose surface has a fractal dimension at least equal to 2.6.
  • the parts obtained according to the process of the present invention support a seizing load according to the FAVILLE LEVALLY machine test according to standard AST -D-2670 at least equal to approximately 3000 daN with a tolerance at most equal to approximately 5% and a number of cycles according to the Hamsler test at least equal to about 300.
  • the coating is selected from those whose surface has a fractal dimension of between 2.65 and 2.75.
  • the coating is selected from those having a stoichiometry corresponding to an Fe / S ratio of between approximately 0.69 and 0.85.
  • the coating will also be favorably selected from those having a thickness of less than about 15 ⁇ m, better still, less than about 6 ⁇ m.
  • the fractal dimension is obtained from a roughness meter, for example a non-contact confocal type 3D roughness meter, the characteristics of which are as follows: Lateral resolution 300 nm
  • the data obtained using the roughness meter are then introduced into a specific calculation algorithm which extracts the mathematical quantities necessary for obtaining the fractal dimension.
  • a high resolution roughness meter is essential to guarantee an accurate measurement of the fractal dimension.
  • a contactless roughness tester is also important to use a contactless roughness tester to ensure that no change in surface morphology has been produced when measuring roughness profiles.
  • the iron sulfide coatings of ferrous alloy parts are obtained by treatments known to those skilled in the art, for example by electrolytic sulfurization in a bath of molten salts according to patent FR-A-1 406 530, or else sulfurization in brine or sulfurization in a salt bath, as the Applicant has demonstrated in its experiments.
  • the present invention also relates to the parts selected according to the method described.
  • Example 1 illustrates the invention without limitation.
  • Cylindrical specimens (cylinders) with a diameter of 6.35 mm and a height of 40 mm made of hardened rectified hardened 16 NC6 steel were treated under the conditions below:
  • test pieces have a coating of iron sulphide.
  • the test pieces are then oiled and then subjected to the test on a FAVILLE LEVALLY machine (according to ASTM-D-2670) by rotating the treated cylinder between two jaws of hardened and hardened 16NC6 steel without additional treatment.
  • the test consists in increasing the load applied to the cylinder until seizure appears. seizure, the tests having been reproduced 5 times in order to evaluate the average seizure load as well as the measurement dispersion.
  • Each cylinder is characterized before the tests in order to determine the fractal size of the surface of the coating after treatment.
  • the fractal dimension is obtained from a 3D roughness tester of the non-contact confocal type, the characteristics of which are as follows: Lateral resolution 300 nm
  • the data obtained using the roughness meter are then introduced into a specific calculation algorithm which extracts the mathematical quantities necessary for obtaining the fractal dimension.
  • the coatings whose surface has a fractal dimension at least equal to 2.6 are selected.
  • the parts (cylinders) according to the invention have a seizure load according to the FAVILLE LEVALLY machine test according to standard ASTM-D-2670 at least equal to approximately 3000 daN.
  • the cylinders coated with iron sulphide according to the invention have a seizure charge approximately 3 times greater than the best results obtained hitherto with slightly fractal iron sulphide.
  • Example 2 Tests were carried out according to DIN standard 51350 (parts 1 to 5) on a machine known as a "4-ball machine" to complete the seizure tests and check the influence of the Fe / S ratio and the thickness of the layer. iron sulfide.
  • Hardened case-hardened CrMo4 steel discs for HRC 60 with a diameter of 60 mm and a thickness of 10 mm were treated under conditions 1, 2 and 3 described in Example 1 and an additional condition described below: Condition 4: Sulfurization in brine.
  • the coatings are selected from those whose surface has a fractal dimension at least equal to 2.6.
  • the coatings are selected from those whose surface has a fractal dimension at least equal to 2.6.

Abstract

A method for obtaining a ferrous alloy part that supports a very high seizure load with very low dispersion includes steps of covering the part with an iron sulphide coating having an appropriate thickness and Fe/S ratio, where the coating is selected from among those with surfaces having a fractal dimension that is at least equal to 2.6.

Description

"Procédé de traitement de pièces en alliage ferreux pour améliorer leurs propriétés frottantes, sans perte de leur dureté ni déformation" "Process for treating ferrous alloy parts to improve their friction properties, without losing their hardness or deformation"
La présente invention concerne un procédé de traitement de pièces en alliage ferreux pour améliorer leurs propriétés frottantes, principalement leur résistance au grippage et au collage, sans risque de perte de leur dureté ni de déformation.The present invention relates to a method of treating ferrous alloy parts to improve their friction properties, mainly their resistance to seizing and sticking, without the risk of losing their hardness or deformation.
L'invention s'applique aux pièces en acier ou en fonte à hautes caractéristiques mécaniques, c'est-à-dire, dont la température de revenu est inférieure à 200°C.The invention applies to steel or cast iron parts with high mechanical characteristics, that is to say, whose tempering temperature is less than 200 ° C.
L'homme du métier sait que deux pièces en acier frottant l'une contre l'autre en l'absence de lubrifiant vont gripper très rapidement. L'homme du métier sait également que le rôle des lubrifiants consiste à séparer les surfaces en contact par un film qui favorise le glissement et l'élimination des calories. Le film de lubrifiant permet de prévenir l'apparition des micro soudures responsables du grippage et du transfert de matière. Pour être efficace, le film de lubrifiant doit avoir une épaisseur supérieure à la hauteur des rugosités de surface. L'épaisseur du film dépend en grande partie des propriétés physico-chimiques superficielles et de la morphologie des surfaces à l'échelle microscopique. Cependant, l'acier brut d'usinage a des caractéristiques de surface telles que l'épaisseur des films de lubrifiant est généralement insuffisante pour assurer une lubrification continue lorsque les charges ou les vitesses deviennent importantes.Those skilled in the art know that two steel parts rubbing against each other in the absence of lubricant will seize up very quickly. Those skilled in the art also know that the role of lubricants consists in separating the surfaces in contact with a film which promotes sliding and the elimination of calories. The film of lubricant prevents the appearance of micro-welds responsible for seizing and transfer of material. To be effective, the lubricant film must have a thickness greater than the height of the surface roughness. The thickness of the film largely depends on the surface physicochemical properties and the morphology of the surfaces on a microscopic scale. However, the machined raw steel has surface characteristics such that the thickness of the lubricant films is generally insufficient to ensure continuous lubrication when the loads or speeds become high.
Des traitements à la surface des aciers ont été mis au point dans le but d'améliorer soit l'absorption du lubrifiant soit les caractéristiques anti-soudure ou encore les deux à la fois. Deux catégories de traitement sont aujourd'hui utilisées dans l'industrie mécanique pour améliorer la rétention de lubrifiant : la phosphatation et la sulfuration à basse température. La phosphatation est principalement destinée à accroître la résistance au grippage des contacts lubrifiés, la sulfuration confère en plus des propriétés d'inhibition de soudure à la surface grâce à la formation de sulfure de fer (FeS hexagonal), et les propriétés anti-grippage sont alors supérieures à celles obtenues avec la phosphatation. Les propriétés physico-chimiques de composés tels le phosphate de fer ou le sulfure de fer sont à l'origine du meilleur mouillage des lubrifiants, l'énergie superficielle de ces constituants étant bien supérieure à celle de l'acier. Ces constituants présentent en outre une faible résistance au cisaillement ainsi qu'une excellente aptitude à l'accommodation, ce qui leur permet d'améliorer les conditions de rodage et la tenue à l'usure des contacts soumis à la fatigue de surface.Surface treatments of the steels have been developed with the aim of improving either the absorption of the lubricant or the anti-weld characteristics or both. Two categories of treatment are used today in the mechanical industry to improve the retention of lubricant: phosphating and sulfurization at low temperature. Phosphatation is mainly intended to increase the seizure resistance of the lubricated contacts, the sulfurization confers in addition properties of inhibition of solder on the surface thanks to the formation of iron sulphide (hexagonal FeS), and the anti-seizure properties are then superior to those obtained with phosphating. The physicochemical properties of compounds such as iron phosphate or iron sulfide are responsible for the better wetting of lubricants, the surface energy of these constituents being much greater than that of steel. These constituents also have a low shear strength as well as an excellent ability to accommodate, which allows them to improve the running-in conditions and the wear resistance of the contacts subjected to surface fatigue.
La sulfuration électrolytique en sels fondus dans une saumure est enseignée dans le FR-A-1 406 530.Electrolytic sulfurization in molten salts in brine is taught in FR-A-1 406 530.
La sulfuration à basse température est réalisée dans un mélange de sels fondus à une température autour de 200°C avec l'assistance d'un électrolyse anodique conduisant à la formation de sulfure de fer hexagonal FeS.Sulfurization at low temperature is carried out in a mixture of molten salts at a temperature around 200 ° C with the assistance of an anodic electrolysis leading to the formation of hexagonal iron sulfide FeS.
Ce dernier procédé est enseigné dans le brevet de la DemanderesseThis latter process is taught in the Applicant's patent
FR-A-2 050 754.FR-A-2 050 754.
Néanmoins, les pièces comportant un revêtement selon l'art antérieur ne répondent plus aux nouvelles exigences, en particulier en ce qui concerne les mécanismes mis en œuvre dans les nouvelles générations de moteurs à injection directe.However, the parts comprising a coating according to the prior art no longer meet the new requirements, in particular as regards the mechanisms implemented in the new generations of direct injection engines.
Un objet de l'invention est d'obtenir des pièces en alliage ferreux ayant des propriétés frottantes améliorées dans des conditions extrêmes de pression et de vitesse, principalement leur résistance au grippage et au collage sans perte de leur dureté ni déformation.An object of the invention is to obtain ferrous alloy parts having improved friction properties under extreme conditions of pressure and speed, mainly their resistance to seizing and sticking without loss of their hardness or deformation.
Cet objet, ainsi que d'autres qui apparaîtront à la lecture de la description ci-après, est satisfait par le procédé de la présente invention.This object, as well as others which will appear on reading the description below, is satisfied by the method of the present invention.
La Demanderesse a constaté de façon surprenante que pour des pièces en alliage ferreux comportant un revêtement en sulfure de fer, la dimension fractale de la surface du revêtement de sulfure de fer jouait un rôle prépondérant, et en tout cas bien plus influent que celui de la stœchiométrie, de la structure cristalline ou encore de la pureté.The Applicant has surprisingly found that for ferrous alloy parts comprising an iron sulphide coating, the fractal dimension of the surface of the iron sulphide coating plays a role. preponderant, and in any case much more influential than that of stoichiometry, crystal structure or even purity.
La Demanderesse a donc mis au point un procédé d'obtention d'une pièce en alliage ferreux supportant une charge de grippage très élevée avec une dispersion très faible ainsi qu'un nombre de cycles élevé, consistant à déposer sur ladite pièce un revêtement de sulfure de fer ayant une épaisseur et un rapport Fe/S appropriés, caractérisé en ce que l'on sélectionne le revêtement parmi ceux dont la surface a une dimension fractale au moins égale à 2,6. Par exemple, les pièces obtenues selon le procédé de la présente invention supportent une charge de grippage selon le test sur machine FAVILLE LEVALLY selon la norme AST -D-2670 au moins égale à environ 3000 daN avec une tolérance au plus égale à environ 5 % et un nombre de cycles selon le test de Hamsler au moins égal à environ 300. L'homme du métier déterminera aisément l'épaisseur et le rapport Fe/S appropriés. Comme le montrent les Exemples ci-après, une épaisseur trop faible est insuffisante pour garantir la résistance au grippage malgré une dimension fractale au moins égale à 2,6, et une épaisseur trop élevée empêche d'obtenir une dimension fractale au moins égale à 2,6. Ces paramètres devront être ajustés expérimentalement, au cas par cas.The Applicant has therefore developed a process for obtaining a piece of ferrous alloy bearing a very high seizing charge with a very low dispersion as well as a high number of cycles, consisting in depositing on said piece a coating of sulphide of iron having an appropriate thickness and Fe / S ratio, characterized in that the coating is selected from those whose surface has a fractal dimension at least equal to 2.6. For example, the parts obtained according to the process of the present invention support a seizing load according to the FAVILLE LEVALLY machine test according to standard AST -D-2670 at least equal to approximately 3000 daN with a tolerance at most equal to approximately 5% and a number of cycles according to the Hamsler test at least equal to about 300. A person skilled in the art will easily determine the appropriate thickness and Fe / S ratio. As shown in the Examples below, a thickness that is too small is insufficient to guarantee seizure resistance despite a fractal dimension at least equal to 2.6, and a thickness that is too high prevents the obtaining of a fractal dimension at least equal to 2 6. These parameters will have to be adjusted experimentally, on a case-by-case basis.
Avantageusement, on sélectionne le revêtement parmi ceux dont la surface a une dimension fractale comprise entre 2,65 et 2,75.Advantageously, the coating is selected from those whose surface has a fractal dimension of between 2.65 and 2.75.
Dans un mode de réalisation préféré de l'invention, on sélectionne le revêtement parmi ceux ayant une stœchiométrie correspondant à un rapport Fe/S compris entre environ 0,69 et 0,85.In a preferred embodiment of the invention, the coating is selected from those having a stoichiometry corresponding to an Fe / S ratio of between approximately 0.69 and 0.85.
Le revêtement sera également favorablement sélectionné parmi ceux ayant une épaisseur inférieure à environ 15 μm, mieux encore, inférieure à environ 6 μm.The coating will also be favorably selected from those having a thickness of less than about 15 μm, better still, less than about 6 μm.
La dimension fractale est obtenue à partir d'un rugosimètre, par exemple un rugosimètre 3D de type confocal sans contact dont les caractéristiques sont les suivantes : Résolution latérale 300 nmThe fractal dimension is obtained from a roughness meter, for example a non-contact confocal type 3D roughness meter, the characteristics of which are as follows: Lateral resolution 300 nm
Résolution verticale 30 nmVertical resolution 30 nm
Débattement vertical 1 mm1 mm vertical travel
Les données obtenues à l'aide du rugosimètre sont ensuite introduites dans un algorithme de calcul spécifique qui en extrait les grandeurs mathématiques nécessaires à l'obtention de la dimension fractale. II faut noter que l'usage d'un rugosimètre de grande résolution est essentiel pour garantir une mesure précise de la dimension fractale. Il est également important d'utiliser un rugosimètre sans contact pour garantir qu'aucune modification de la morphologie de surface n'a été produite lors de la mesure des profils de rugosité. Les revêtements en sulfure de fer des pièces en alliage ferreux sont obtenus par des traitements connus de l'homme du métier, par exemple par sulfuration électrolytique en bain de sels fondus selon brevet FR-A-1 406 530, ou bien sulfuration dans une saumure ou encore sulfuration en bain de sels comme la Demanderesse l'a démontré dans ses expérimentations. La présente invention concerne également les pièces sélectionnées selon le procédé décrit.The data obtained using the roughness meter are then introduced into a specific calculation algorithm which extracts the mathematical quantities necessary for obtaining the fractal dimension. It should be noted that the use of a high resolution roughness meter is essential to guarantee an accurate measurement of the fractal dimension. It is also important to use a contactless roughness tester to ensure that no change in surface morphology has been produced when measuring roughness profiles. The iron sulfide coatings of ferrous alloy parts are obtained by treatments known to those skilled in the art, for example by electrolytic sulfurization in a bath of molten salts according to patent FR-A-1 406 530, or else sulfurization in brine or sulfurization in a salt bath, as the Applicant has demonstrated in its experiments. The present invention also relates to the parts selected according to the method described.
Les Exemples suivants illustrent l'invention de façon non limitative. Exemple 1The following examples illustrate the invention without limitation. Example 1
Des éprouvettes cylindriques (cylindres) de diamètre 6,35 mm et de hauteur 40 mm en acier 16 NC6 cémenté trempé rectifié ont été traitées dans les conditions ci-dessous :Cylindrical specimens (cylinders) with a diameter of 6.35 mm and a height of 40 mm made of hardened rectified hardened 16 NC6 steel were treated under the conditions below:
Condition 1 : Sulfuration électrolytique en sels fondus selon brevet FR-A-1 406 530 - Température de traitement : 190°CCondition 1: Electrolytic sulfurization in molten salts according to patent FR-A-1 406 530 - Treatment temperature: 190 ° C.
- Temps d'immersion : 15 minutes- Immersion time: 15 minutes
- Composition de la saumure (% massique) : SCN" = 62,75 %- Composition of brine (% by mass): SCN " = 62.75%
Na+ = 7,1 % K+ = 30,15 % - Densité de courant : 2,8 à 3,2 A/dm2 Condition 2 : Sulfuration dans une saumureNa + = 7.1% K + = 30.15% - Current density: 2.8 to 3.2 A / dm 2 Condition 2: Sulfurization in brine
- Température de traitement : 100 à 135°C- Processing temperature: 100 to 135 ° C
- Temps d'immersion : 3 à 10 heures - Composition de la saumure (% massique) : OH" = 8,50 %- Immersion time: 3 to 10 hours - Composition of brine (% by mass): OH " = 8.50%
S2O8 2- = 12,10 % S2O3 2" = 8,86 % CI- = 1 ,52 % Na+ = 19,02 % Condition 3 : Sulfuration en bain de selsS 2 O 8 2 - = 12.10% S 2 O 3 2 " = 8.86% CI- = 1.52% Na + = 19.02% Condition 3: Sulfurization in salt bath
- Température de traitement : 180 à 280° C- Processing temperature: 180 to 280 ° C
- Temps d'immersion : 1 ,5 à 3 heures- Immersion time: 1.5 to 3 hours
- Composition de la saumure (% massique) : OH" = 2,10 %- Composition of brine (% by mass): OH " = 2.10%
S2O8 2" = 24,20 % S2O3 2- = 17,75 %S 2 O 8 2 " = 24.20% S 2 O 3 2 - = 17.75%
HSO4 "= 33,75 % NH4 = = 6,25 % Na+ = 15,95 % Après traitement, les eprouvettes comportent un revêtement de sulfure de fer. Les eprouvettes sont ensuite huilées puis soumises au test sur machine FAVILLE LEVALLY (selon ASTM-D-2670) en faisant tourner le cylindre traité entre deux mors en acier 16NC6 cémenté et trempé sans traitement supplémentaire. Le test consiste à faire croître la charge appliquée sur le cylindre jusqu'à apparition du grippage. On détermine alors la charge de grippage, les essais ayant été reproduits 5 fois afin d'évaluer la charge moyenne de grippage ainsi que la dispersion de mesure.HSO 4 " = 33.75% NH 4 = = 6.25% Na + = 15.95% After treatment, the test pieces have a coating of iron sulphide. The test pieces are then oiled and then subjected to the test on a FAVILLE LEVALLY machine (according to ASTM-D-2670) by rotating the treated cylinder between two jaws of hardened and hardened 16NC6 steel without additional treatment. The test consists in increasing the load applied to the cylinder until seizure appears. seizure, the tests having been reproduced 5 times in order to evaluate the average seizure load as well as the measurement dispersion.
Chaque cylindre est caractérisé avant les essais afin de déterminer la grandeur fractale de la surface du revêtement après traitement. La dimension fractale est obtenue à partir d'un rugosimètre 3D de type confocal sans contact dont les caractéristiques sont les suivantes : Résolution latérale 300 nmEach cylinder is characterized before the tests in order to determine the fractal size of the surface of the coating after treatment. The fractal dimension is obtained from a 3D roughness tester of the non-contact confocal type, the characteristics of which are as follows: Lateral resolution 300 nm
Résolution verticale 30 nmVertical resolution 30 nm
Débattement vertical 1 mm1 mm vertical travel
Les données obtenues à l'aide du rugosimètre sont ensuite introduites dans un algorithme de calcul spécifique qui en extrait les grandeurs mathématiques nécessaires à l'obtention de la dimension fractale.The data obtained using the roughness meter are then introduced into a specific calculation algorithm which extracts the mathematical quantities necessary for obtaining the fractal dimension.
Selon l'invention, on sélectionne les revêtements dont la surface a une dimension fractale au moins égale à 2,6.According to the invention, the coatings whose surface has a fractal dimension at least equal to 2.6 are selected.
Les résultats obtenus sont groupés dans le Tableau I suivant et comparés, dans les mêmes conditions d'essai. A titre comparatif, des eprouvettes non traitées grippent dès le démarrage de l'essai. The results obtained are grouped in the following Table I and compared, under the same test conditions. By way of comparison, untreated test pieces seize up at the start of the test.
TableauBoard
Les pièces (cylindres) conformes à l'invention présentent une charge de grippage selon le test sur machine FAVILLE LEVALLY selon la norme ASTM-D-2670 au moins égale à environ 3000 daN. The parts (cylinders) according to the invention have a seizure load according to the FAVILLE LEVALLY machine test according to standard ASTM-D-2670 at least equal to approximately 3000 daN.
On observe en outre que les cylindres revêtus de sulfure de fer conforme à l'invention ont une charge de grippage environ 3 fois supérieure aux meilleurs résultats obtenus jusqu'alors avec du sulfure de fer peu fractal.It is further observed that the cylinders coated with iron sulphide according to the invention have a seizure charge approximately 3 times greater than the best results obtained hitherto with slightly fractal iron sulphide.
Par ailleurs, la dispersion des résultats est 4 fois moins grande lorsque le sulfure de fer à une grandeur (dimension) fractale supérieure à 2,6. Exemple 2 Des essais ont été conduits selon la norme DIN 51350 (parties 1 à 5) sur machine dite "machine 4 billes" pour compléter les tests de grippage et vérifier l'influence du rapport Fe/S et de l'épaisseur de la couche de sulfure de fer.Furthermore, the dispersion of the results is 4 times less when the iron sulfide has a fractal size (dimension) greater than 2.6. Example 2 Tests were carried out according to DIN standard 51350 (parts 1 to 5) on a machine known as a "4-ball machine" to complete the seizure tests and check the influence of the Fe / S ratio and the thickness of the layer. iron sulfide.
Des disques en acier 15 CrMo4 cémenté trempé pour HRC 60 de diamètre 60 mm et d'épaisseur 10 mm ont été traités dans les conditions 1 , 2 et 3 décrites dans l'Exemple 1 et une condition supplémentaire décrite ci-après : Condition 4 : Sulfuration dans une saumure.Hardened case-hardened CrMo4 steel discs for HRC 60 with a diameter of 60 mm and a thickness of 10 mm were treated under conditions 1, 2 and 3 described in Example 1 and an additional condition described below: Condition 4: Sulfurization in brine.
- T° de traitement : 100 à 130°C- Treatment temperature: 100 to 130 ° C
- Temps d'immersion : 3 h10- Immersion time: 3 h 10
- Composition de la saumure (% massique) : OH" = 10,52% S2O8 2" = 9,8 %- Composition of brine (% by mass): OH " = 10.52% S 2 O 8 2" = 9.8%
S2O3 2" = 5,74 % CI' = 0,55 % Na+ = 19,12 % Après traitement, les pièces comportent un revêtement de sulfure de fer. Les essais sont conduits dans un bain d'huile minérale pure à 60° C. Les charges de grippage moyennes et les dispersions obtenues avec 5 essais sont regroupées dans le tableau suivant. La dimension fractale de la surface du revêtement a été mesurée à l'aide du même dispositif que celui décrit à l'Exemple 1. Les résultats sont donnés dans le Tableau II. Tableau IIS 2 O 3 2 " = 5.74% CI ' = 0.55% Na + = 19.12% After treatment, the parts have a coating of iron sulfide. The tests are carried out in a bath of pure mineral oil at 60 ° C. The average binding loads and the dispersions obtained with 5 tests are grouped in the following table: The fractal dimension of the surface of the coating was measured using the same device as that described in Example 1 The results are given in Table II. Table II
Selon l'invention, on sélectionne les revêtements parmi ceux dont la surface a une dimension fractale au moins égale à 2,6. According to the invention, the coatings are selected from those whose surface has a fractal dimension at least equal to 2.6.
On constate qu'en sélectionnant en outre des pièces ayant un revêtement dont le rapport Fe/S est dans la plage 0,69 à 0,85 la charge de grippage et la dispersion ne sont pas affectées. Il en est de même pour des épaisseurs du revêtement comprises entre 1 ,5 et 15 μm. En revanche, une épaisseur de 0,5 μm est insuffisante pour garantir une résistance au grippage, et, pour une épaisseur de 20 μm il n'est pas possible d'obtenir du sulfure de fer de grandeur fractale au moins égale à 2,6. Exemple 3It can be seen that by further selecting parts having a coating whose Fe / S ratio is in the range 0.69 to 0.85, the seizing charge and the dispersion are not affected. The same is true for coating thicknesses of between 1.5 and 15 μm. On the other hand, a thickness of 0.5 μm is insufficient to guarantee seizure resistance, and for a thickness of 20 μm it is not possible to obtain iron sulfide of fractal size at least equal to 2.6 . Example 3
Pour caractériser la pertinence de la sélection des pièces ayant un revêtement de sulfure de fer fractal à supporter des conditions difficiles de contacts avec lubrification aléatoire, un essai de simulation a été conduit en faisant glisser deux cylindres de diamètre identique l'un contre l'autre à une vitesse de 5 m.s'1 sous une pression de 1200 MPa. Le contact est alimenté en huile 600 NS à 80° C (16 cSt) pendant la phase de rodage de 1 heure puis la lubrification est arrêtée. La lubrification est remise en service dès que le coefficient de frottement atteint la valeur critique de 0,085 (frottement en lubrification limite) puis est à nouveau stoppée lorsque celui-ci atteint une valeur stabilisée autour de 0,04. L'opération est ensuite répétée et le nombre de cycles avant grippage irréversible est comptabilisé.To characterize the relevance of the selection of parts with a fractal iron sulfide coating to withstand difficult contact conditions with random lubrication, a simulation test was conducted by sliding two cylinders of identical diameter against each other at a speed of 5 ms ' 1 under a pressure of 1200 MPa. The contact is supplied with 600 NS oil at 80 ° C (16 cSt) during the 1 hour running-in phase, then the lubrication is stopped. Lubrication is put back into service as soon as the friction coefficient reaches the critical value of 0.085 (friction in limit lubrication) then is stopped again when this reaches a stabilized value around 0.04. The operation is then repeated and the number of cycles before irreversible seizure is counted.
Les cylindres ont été traités et sélectionnés dans les conditions 1 , 2 et 3 décrites précédemment. La dimension fractale de la surface du revêtement de chaque cylindre a été mesurée à l'aide du dispositif décrit dans l'Exemple 1. Les résultats obtenus sont regroupés dans le Tableau III. TableauThe cylinders were treated and selected under conditions 1, 2 and 3 described above. The fractal dimension of the surface of the coating of each cylinder was measured using the device described in Example 1. The results obtained are collated in Table III. Board
Selon l'invention, on sélectionne les revêtements parmi ceux dont la surface a une dimension fractale au moins égale à 2,6. According to the invention, the coatings are selected from those whose surface has a fractal dimension at least equal to 2.6.

Claims

Revendications claims
1. Procédé d'obtention d'une pièce en alliage ferreux supportant une charge de grippage très élevée avec une tolérance très faible ainsi qu'un nombre de cycles élevé, consistant à déposer sur ladite pièce un revêtement de sulfure de fer ayant une épaisseur et un rapport Fe/S appropriés, caractérisé en ce que l'on sélectionne le revêtement parmi ceux dont la surface a une dimension fractale au moins égale à 2,6. 1. Method for obtaining a piece of ferrous alloy bearing a very high binding load with a very low tolerance as well as a high number of cycles, consisting in depositing on said piece a coating of iron sulfide having a thickness and an appropriate Fe / S ratio, characterized in that the coating is selected from those whose surface has a fractal dimension at least equal to 2.6.
2. Procédé selon la revendication 1 , caractérisé en ce que l'on sélectionne le revêtement parmi ceux dont la surface a une dimension fractale comprise entre 2,65 et 2,75.2. Method according to claim 1, characterized in that the coating is selected from those whose surface has a fractal dimension between 2.65 and 2.75.
3. Procédé selon l'une des revendications 1 et 2, caractérisé en ce que l'on sélectionne le revêtement parmi ceux ayant une stœchiométrie correspondant à un rapport Fe/S compris entre environ 0,69 et 0,85.3. Method according to one of claims 1 and 2, characterized in that the coating is selected from those having a stoichiometry corresponding to an Fe / S ratio between about 0.69 and 0.85.
4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que l'on sélectionne le revêtement parmi ceux ayant une épaisseur inférieure à environ 15 μm.4. Method according to any one of claims 1 to 3, characterized in that the coating is selected from those having a thickness less than about 15 microns.
5. Procédé selon la revendication 4, caractérisé en ce que l'on sélectionne le revêtement parmi ceux ayant une épaisseur inférieure à environ 6 μm.5. Method according to claim 4, characterized in that the coating is selected from those having a thickness of less than about 6 μm.
6. Pièce obtenue selon l'une quelconque des revendications 1 à 5. 6. Part obtained according to any one of claims 1 to 5.
EP02727644A 2001-04-04 2002-03-28 Method for treating ferrous alloy parts in order to improve the rubbing properties thereof without causing hardness loss or deformation Expired - Lifetime EP1386018B1 (en)

Applications Claiming Priority (3)

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FR0104580 2001-04-04
FR0104580A FR2823227B1 (en) 2001-04-04 2001-04-04 PROCESS FOR TREATING FERROUS ALLOY PARTS TO IMPROVE THEIR FRICTIONAL PROPERTIES WITHOUT LOSS OF HARDNESS OR DEFORMATION
PCT/FR2002/001091 WO2002081769A2 (en) 2001-04-04 2002-03-28 Method for treating ferrous alloy parts in order to improve the rubbing properties thereof without causing hardness loss or deformation

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EP1386018B1 EP1386018B1 (en) 2010-05-19

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FR2860806B1 (en) * 2003-10-14 2006-01-06 Stephanois Rech Mec PROCESS FOR TREATING SULFURATION OF FERROUS ALLOY PARTS
FR2909102B1 (en) 2006-11-24 2009-03-06 Hef Soc Par Actions Simplifiee PROCESS FOR THE SULFURATION OF FERROUS ALLOY PARTS IN AQUEOUS SOLUTION
CN102084018B (en) * 2009-06-29 2013-12-11 新日铁住金株式会社 Zinc-aluminum galvanized iron wire and manufacturing method therefor

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US5981934A (en) * 1996-09-12 1999-11-09 Canon Kabushiki Kaisha Photovoltaic element having a transparent conductive layer with specified fractal dimension and fractal property
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ES2344832T3 (en) 2010-09-08
US20040146753A1 (en) 2004-07-29
WO2002081769A2 (en) 2002-10-17
CA2443005A1 (en) 2002-10-17
TWI275664B (en) 2007-03-11
US7172794B2 (en) 2007-02-06
AU2002257854A1 (en) 2002-10-21
MY137691A (en) 2009-02-27
JP2004526059A (en) 2004-08-26
DE60236425D1 (en) 2010-07-01
JP4545376B2 (en) 2010-09-15
FR2823227B1 (en) 2004-04-02
CA2443005C (en) 2009-02-03

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