EP0043742A1 - Method of gas-chromizing steels - Google Patents

Method of gas-chromizing steels Download PDF

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Publication number
EP0043742A1
EP0043742A1 EP81400804A EP81400804A EP0043742A1 EP 0043742 A1 EP0043742 A1 EP 0043742A1 EP 81400804 A EP81400804 A EP 81400804A EP 81400804 A EP81400804 A EP 81400804A EP 0043742 A1 EP0043742 A1 EP 0043742A1
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Prior art keywords
chromium
powder
gas
carbon content
ferro
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German (de)
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EP0043742B1 (en
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Robert Leveque
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Creusot Loire SA
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Creusot Loire SA
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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
    • C23C12/00—Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material surfaces

Definitions

  • the present invention relates to an improvement in chromium-plating by gas of steels with more than 0.2% carbon, more especially structural steels and tool steels.
  • the aim of the present invention is to produce single-phase layers of Cr 2 (C, N) by reducing the surface supply of chromium.
  • the subject of the invention is an improvement to the gas chromium-plating process of steels with more than 0.2% carbon, consisting of the three successive treatments according to the prior patent, this improvement having the aim of reducing 'superficial supply of chromium, and being characterized in that, in the gas chromization treatment using a cement based on ferro-chromium at 50% / 75% chromium, with a particle size between 0.5 millimeter and 4 millimeters, a ferro-chromium is chosen whose carbon content is between 1% and 3%, and is preferably close to 2%.
  • the cement used in the gas chromization treatment consists of a mixture pulverulent of a ferro-chromium powder having a chromium content of between 50% and 75%, a carbon content of between 1% and 3%, and a particle size of between 0.5 millimeter and 4 millimeters, without aluminous binder nor magnesium, and of an ammonium chloride powder, the latter powder being in said pulverulent mixture at a concentration of between 0.5% and 1.5%.
  • the cement used in the gas chromization treatment consists of a powder mixture of the same ferro-chromium powder as above, and a powder of magnesium chloride or ammonium fluoride, the latter powder being in said pulverulent mixture at a concentra between 0.5% and 1.5%.
  • the main improvement introduced by the present invention with respect to the prior patent consists in using only ferro-chromium whose carbon content is between 1% and 3%, and is preferably close to 2% .
  • This presence of ferro-chromium carbon makes it possible to obtain, in gas chromization, a perfectly single-phase layer of chromium carbonitrides Cr 2 (C, N), and to avoid the formation of carbides M 23 C 6 (M denoting a metal such as iron (Fe), chromium (Cr), nickel (Ni), etc.).
  • a secondary improvement according to the present invention compared to the previous patent consists, for steels with a carbon content of between 0.20% and 0.35%, while retaining ammonium chloride as halide, to use it at a slightly increased concentration, between 0.5% and 1.5%, instead of 0.4% to 1%.
  • Another improvement according to the present invention compared to the prior patent consists, for steels with a carbon content greater than 0.35%, of replacing ammonium chloride either with magnesium chloride or with ammonium fluoride, which are more stable halides than ammonium chloride.
  • the first example relates to a chromium-molybdenum-vanadium steel, of the 32 CDV 13 type, therefore with 0.32% carbon.
  • This steel underwent the first sequence of ionic nitriding under the conditions defined above and more precisely between 520 and 530 ° C, for 30 hours, under a partial nitrogen pressure of between 0.1 and 0.5 millibar, the pressure of work being between 2.5 and 8 millibars. Under these conditions, the average nitrogen content of the steel between 50 and 200 microns deep reaches 2.1% and the nitrided layer does not contain iron nitrides or chromium nitrides.
  • the second example relates to a chromium-molybdenum-vanadium steel of the type 40 CDV 12, therefore with 0.40% carbon.
  • This steel underwent the first sequence of ionic nitriding under the conditions which were specified during the description of the first example.
  • the 40 CDV 12 steel sample thus nitrided is introduced into a case hardening box where the second phase of the treatment will take place, which is a gas chromization.
  • the cementing agent consists of 99% ferrochrome with 65/70% chromium and 2% carbon with an average particle size of around 2.7 mm (extremes: 0.5 and 4 mm) and 1% chloride of magnesium, which, when the temperature rises, will decompose to give the active vapor of chromium chloride CrC1 2 .
  • the enclosure is brought to an average temperature of 950 ° C for a period of 15 hours and the subsequent heat treatment of the steel part is carried out immediately after the chromization phase.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

A process for the chromization by gas of steels containing more than 0.2% of carbon, consisting of three successive treatments, the chromization treatment proper employing a cement having a ferrochrome base containing between 1% and 3% of carbon, and preferably 2%. The process is particularly useful in the chromization of structural and tool steels.

Description

La présente invention concerne un perfectionnement à la chromisation par voie gazeuse des aciers à plus de 0,2 % de carbone, plus spécialement les aciers de construction et les aciers à outils.The present invention relates to an improvement in chromium-plating by gas of steels with more than 0.2% carbon, more especially structural steels and tool steels.

Dans une demande de brevet antérieur, la demanderesse a décrit un procédé de chromisation en trois temps successifs, constitués de préférence ainsi :

  • 1°/ Une nitruration ionique, à une température comprise entre 450 et 650°C, utilisant une atmosphère réactive d'azote et d'hydrogène sous une pression partielle d'azote au plus égale à 1,5 millibar et sous une pression gazeuse totale comprise entre 2 et 10 millibars.
  • 2°/ Une chromisation à une température comprise entre 900° et 1000°C avec un cément constitué par du ferrochrome avec une teneur en chrome allant de 50 à 75 % et dont 1a granulométrie est comprise entre 0,5 et 4 mm, sans liant alumineux ni magnésien, mélangé à un halogénure.
  • 3°/ Un traitement thermique de trempe à une température comprise entre 800 et 1000°C et de revenu entre 580 et 650°C selon le niveau de résistance demandé pour le substrat.
In an earlier patent application, the applicant has described a chromization process in three successive stages, preferably consisting of:
  • 1 ° / An ionic nitriding, at a temperature between 450 and 650 ° C, using a reactive atmosphere of nitrogen and hydrogen under a partial pressure of nitrogen at most equal to 1.5 millibar and under a total gas pressure between 2 and 10 millibars.
  • 2 ° / Chromization at a temperature between 900 ° and 1000 ° C with a cement formed by ferrochrome with a chromium content ranging from 50 to 75% and whose particle size is between 0.5 and 4 mm, without binder aluminous or magnesian, mixed with a halide.
  • 3 ° / A quenching heat treatment at a temperature between 800 and 1000 ° C and tempering between 580 and 650 ° C depending on the level of resistance required for the substrate.

Il est ainsi possible d'augmenter sensiblement l'épaisseur des couches chromisées de haute dureté dans le cas des aciers alliés ayant plus de 0,2 % de carbone. En effet, grâce à cette innovation, il est possible de réaliser des couches d'épaisseur égale à 50 microns alors que dans le meilleur des cas, la chromisation classique permet d'atteindre 20 microns. D'autre part, l'innovation selon le brevet antérieur intéresse également la structure des couches :

  • - dans la chromisation classique, les revêtements sont constitués de deux types de carbures : M23C6, plus riche en chrome, vers la surface, et M7C3, plus pauvre en chrome, vers le substrat métallique.
  • - A la suite du traitement en trois stades faisant l'objet du brevet principal, les revêtements sont constitués essentiellement par le carbo- nitrure de chrome Cr2(C, N), dont la très forte teneur en chrome (Cr compris entre 75 et 85 %), le niveau élevé de dureté, compris entre 2000 et 2500 Vickers (sous 50 grammes) et la structure hexagonale avec le plan de base de la maille dirigé parallèlement à la surface du substrat, en font,un composé particulièrement intéressant pour tous les problèmes où l'on recherche une bonne résistance à la fois à la corrosion, au frottement et à l'usure.
It is thus possible to appreciably increase the thickness of the chromium layers of high hardness in the case of alloy steels having more than 0.2% of carbon. In fact, thanks to this innovation, it is possible to produce layers with a thickness equal to 50 microns, while in the best case, conventional chromization allows 20 microns to be reached. On the other hand, the innovation according to the prior patent also concerns the structure of the layers:
  • - in conventional chromization, the coatings consist of two types of carbides: M 23 C 6 , richer in chromium, towards the surface, and M 7 C 3 , poorer in chromium, towards the metallic substrate.
  • - Following the three-stage treatment covered by the main patent, the coatings consist essentially of chromium carbon nitride Cr 2 (C, N), of which the very high chromium content (Cr between 75 and 85%), the high level of hardness, between 2000 and 2500 Vickers (under 50 grams) and the hexagonal structure with the base plane of the mesh directed parallel to the surface of the substrate, make it a particularly interesting compound for all problems where good resistance is sought at the same time to corrosion, to friction and to wear.

Toutefois, dans les conditions opératoires décrites dans le brevet antérieur, l'obtention de couches monphasées de Cr2 (C, N) peut être délicate dans certains cas en raison de l'apport trop important de chrome en surface par rapport au flux d'azote provenant du substrat qui a subi la première phase de nitruration ionique. Il en résulte que sur les joints des formations basaltiques de Cr2(C, N) se forme localement le carbure M23C6, et la présence dans le revêtement de ce deuxième composé a plusieurs inconvénients :

  • - augmentation sensible de la rugosité superficielle,
  • - augmentation du risque d'amorçage de fissures à l'interface entre les deux constituants M23c6 et Cr2 (C, N), d'où possibilité d'écaillage et de corrosion localisée.
However, under the operating conditions described in the previous patent, obtaining single-phase layers of Cr 2 (C, N) can be difficult in certain cases due to the too large supply of chromium at the surface in relation to the flux of nitrogen from the substrate which has undergone the first phase of ionic nitriding. It follows that on the joints of the basaltic formations of Cr 2 (C, N) locally forms the carbide M 23 C 6 , and the presence in the coating of this second compound has several drawbacks:
  • - significant increase in surface roughness,
  • - increased risk of crack initiation at the interface between the two constituents M 23 c 6 and Cr 2 (C, N), hence the possibility of chipping and localized corrosion.

Le but de la présente invention est la réalisation de couches monophasées de Cr2 (C, N) par une réduction de l'apport superficiel de chrome.The aim of the present invention is to produce single-phase layers of Cr 2 (C, N) by reducing the surface supply of chromium.

A cet effet, l'invention a pour objet un perfectionnement au procédé de chromisation par voie gazeuse des aciers à plus de 0,2 % de carbone, constitué des trois traitements successifs selon le brevet antérieur, ce perfectionnement ayant pour but une réduction de l'apport superficiel de chrome, et étant caractérisé en ce que, dans le traitement de chromisation gazeuse utilisant un cément à base de ferro-chrome à 50 %/75 % de chrome, avec une granulométrie comprise entre 0,5 millimètre et 4 millimètres, on choisit un ferro-chrome dont la teneur en carbone est comprise entre 1 % et 3 %, et est de préférence voisine de 2 %.To this end, the subject of the invention is an improvement to the gas chromium-plating process of steels with more than 0.2% carbon, consisting of the three successive treatments according to the prior patent, this improvement having the aim of reducing 'superficial supply of chromium, and being characterized in that, in the gas chromization treatment using a cement based on ferro-chromium at 50% / 75% chromium, with a particle size between 0.5 millimeter and 4 millimeters, a ferro-chromium is chosen whose carbon content is between 1% and 3%, and is preferably close to 2%.

Suivant une caractéristique particulière de l'invention, qui ne s'applique qu'aux aciers dont la teneur en carbone est comprise entre 0,20 % et 0,35 %, le cément utilisé dans le traitement de chromisation gazeuse est constitué par un mélange pulvérulent d'une poudre de ferro-chrome présentant une teneur en chrome comprise entre 50 % et 75 %, une teneur en carbone comprise entre 1 % et 3 %, et une granulométrie comprise entre 0,5 millimètre et 4 millimètres, sans liant alumineux ni magnésien, et d'une poudre de chlorure d'ammonium, cette dernière poudre se trouvant dans ledit mélange pulvérulent à une concentration comprise entre 0,5 % et 1,5 %.According to a particular characteristic of the invention, which only applies to steels whose carbon content is between 0.20% and 0.35%, the cement used in the gas chromization treatment consists of a mixture pulverulent of a ferro-chromium powder having a chromium content of between 50% and 75%, a carbon content of between 1% and 3%, and a particle size of between 0.5 millimeter and 4 millimeters, without aluminous binder nor magnesium, and of an ammonium chloride powder, the latter powder being in said pulverulent mixture at a concentration of between 0.5% and 1.5%.

Suivant une autre caractéristique particulière de l'invention, qui ne s'applique qu'aux aciers dont la teneur en carbone est supérieure à 0,35 %, le cément utilisé dans le traitement de chromisation gazeuse est constitué par un mélange pulvérulent de la même poudre de ferro-chrome que cr-dessus, et d'une poudre de chlorure de magnésium ou de fluorure d'ammonium, cette dernière poudre se trouvant dans ledit mélange pulvérulent à une concentration comprise entre 0,5 % et 1,5 %.According to another particular characteristic of the invention, which only applies to steels whose carbon content is greater than 0.35%, the cement used in the gas chromization treatment consists of a powder mixture of the same ferro-chromium powder as above, and a powder of magnesium chloride or ammonium fluoride, the latter powder being in said pulverulent mixture at a concentra between 0.5% and 1.5%.

Comme on le comprend, le perfectionnement principal introduit par la présente invention par rapport au brevet antérieur consiste à n'utiliser que des ferro-chromes dont la teneur en carbone est comprise entre 1 % et 3 %, et est de préférence voisine de 2 %. Cette présence du carbone du ferro-chrome permet d'obtenir en chromisation gazeuse une couche parfaitement monophasée de carbonitrures de chrome Cr2 (C, N), et d'éviter la formation de carbures M23C6 (M désignant un métal tel que le fer (Fe), le chrome (Cr), le nickel (Ni), etc ...).As will be understood, the main improvement introduced by the present invention with respect to the prior patent consists in using only ferro-chromium whose carbon content is between 1% and 3%, and is preferably close to 2% . This presence of ferro-chromium carbon makes it possible to obtain, in gas chromization, a perfectly single-phase layer of chromium carbonitrides Cr 2 (C, N), and to avoid the formation of carbides M 23 C 6 (M denoting a metal such as iron (Fe), chromium (Cr), nickel (Ni), etc.).

Un perfectionnement secondaire selon la présente invention par rapport au brevet antérieur consiste, pour les aciers à teneur en carbone comprise entre 0,20 % et 0,35 %, tout en conservant comme halogénure le chlorure d'ammonium, à l'utiliser à une concentration un peu accrue, comprise entre 0,5 % et 1,5 %, au lieu de 0,4 % à 1 %.A secondary improvement according to the present invention compared to the previous patent consists, for steels with a carbon content of between 0.20% and 0.35%, while retaining ammonium chloride as halide, to use it at a slightly increased concentration, between 0.5% and 1.5%, instead of 0.4% to 1%.

Un autre perfectionnement selon la présente invention par rapport au brevet antérieur consiste, pour les aciers à teneur en carbone supérieure à 0,35 %, à remplacer le chlorure d'ammonium soit par du chlorure de magnésium, soit par du fluorure d'ammonium, qui sont des halogénures plus stables que le chlorure d'ammonium.Another improvement according to the present invention compared to the prior patent consists, for steels with a carbon content greater than 0.35%, of replacing ammonium chloride either with magnesium chloride or with ammonium fluoride, which are more stable halides than ammonium chloride.

Pour bien faire comprendre l'intérêt de l'invention selon la présente invention, en vue de réaliser des couches monophasées de Cr2(C, N), voici deux exemples relatifs à deux aciers qui, par leur teneur en carbone, se situent de part et d'autre de la limite de 0,35 % précédemment définie.To clearly understand the advantage of the invention according to the present invention, with a view to producing single-phase layers of Cr 2 (C, N), here are two examples relating to two steels which, by their carbon content, are of on either side of the 0.35% limit previously defined.

Le premier exemple est relatif à un acier au chrome-molybdène- vanadium, du type 32 CDV 13, donc à 0,32 % de carbone. Cet acier a subi la première séquence de nitruration ionique dans les conditions précédemment définies et plus précisément entre 520 et 530°C, pendant 30 heures, sous une pression partielle d'azote comprise entre 0,1 et 0,5 millibar, la pression de travail étant comprise entre 2,5 et 8 millibars. Dans ces conditions, la teneur moyenne en azote de l'acier entre 50 et 200 microns de profondeur atteint 2,1 % et la couche nitrurée ne contient pas de nitrures de fer ni de nitrures de chrome.The first example relates to a chromium-molybdenum-vanadium steel, of the 32 CDV 13 type, therefore with 0.32% carbon. This steel underwent the first sequence of ionic nitriding under the conditions defined above and more precisely between 520 and 530 ° C, for 30 hours, under a partial nitrogen pressure of between 0.1 and 0.5 millibar, the pressure of work being between 2.5 and 8 millibars. Under these conditions, the average nitrogen content of the steel between 50 and 200 microns deep reaches 2.1% and the nitrided layer does not contain iron nitrides or chromium nitrides.

L'échantillon d'acier 32CDV 13 ainsi nitruré est introduit dans une caisse de cémentation où va se faire la deuxième phase du traitement, qui est une chromisation gazeuse. L'agent de cémentation est constitué par 99 % de firro-chrome à 65/70 % de chrome et 2 % de carbone, dont la'granulométrie moyenne est voisine de 2,7 mm (extrêmes : 0,5 et 4 mm) et 1 % de chlorure d'ammonium, qui, lors de la montée en température, va se décomposer pour donner la vapeur active de chlorure de chrome CrC12. L'enceinte est portée à une température moyenne de 950°C pendant une durée de 15 heures, et le traitement thermique ultérieur de la pièce d'acier est effectué immédiatement après la phase de chromisation. Dans ces conditions, on obtient une couche parfaitement monophasée de carbonitrures de chrome Cr2 (C, N) dont l'épaisseur est voisine de 50 microns. Les caractéristiques de cette couche sont les suivantes :

  • - dureté voisine de 2500 Hv dans l'échelle Vic kers sous une charge de 50 grammes,
  • - composition chimique très homogène sur toute son épaisseur avec : 77 % Cr, 10 % Fe, 10 % N et 3 % C.
  • - structure basaltique avec le plan des basaltes dirigé parallèlement au plan de base de la maille hexagonale,
  • - très bonne rugosité superficielle avec un RT inférieur à 4 microns. (le RT est un paramètre qui caractérise la rugosité superficielle d'une surface par la distance qui sépare les plus hauts reliefs des creux les plus profonds notés sur l'enregistrement).
  • - absence de défauts ou de porosités entre les basaltes de Cr2 (C, N).
The 32CDV 13 steel sample thus nitrided is introduced into a case hardening box where the second phase of the treatment will be carried out, which is a gas chromization. The cementation agent consists of 99% firro-chromium with 65/70% chromium and 2% carbon, the average particle size of which is close to 2.7 mm (extremes: 0.5 and 4 mm) and 1% ammonium chloride, which, when the temperature rises, will decompose ser to give the active vapor of chromium chloride CrC1 2 . The enclosure is brought to an average temperature of 950 ° C for a period of 15 hours, and the subsequent heat treatment of the steel part is carried out immediately after the chromization phase. Under these conditions, a perfectly single-phase layer of chromium carbonitrides Cr 2 (C, N) is obtained, the thickness of which is close to 50 microns. The characteristics of this layer are as follows:
  • - hardness close to 2500 Hv in the Vic kers scale under a load of 50 grams,
  • - very homogeneous chemical composition over its entire thickness with: 77% Cr, 10% Fe, 10% N and 3% C.
  • - basalt structure with the basalt plane directed parallel to the base plane of the hexagonal mesh,
  • - very good surface roughness with an RT of less than 4 microns. (the RT is a parameter which characterizes the surface roughness of a surface by the distance which separates the highest reliefs from the deepest hollows noted on the recording).
  • - absence of defects or porosities between the basalts of Cr 2 (C, N).

Une telle structure est évidemment très favorable pour tous les problèmes où l'on recherche à la fois :

  • - une bonne résistance à la corrosion (donnée par la teneur en chrome et l'absence de défauts superficiels),
  • - une bonne résistance au frottement et à l'usure (donnée par la dureté du composé, sa structure cristallographique et la rugosité superficielle).
Such a structure is obviously very favorable for all the problems where one seeks at the same time:
  • - good resistance to corrosion (given by the chromium content and the absence of surface defects),
  • - good resistance to friction and wear (given by the hardness of the compound, its crystallographic structure and the surface roughness).

Le deuxième exemple est relatif à un acier au chrome-molybdène- vanadium du type 40 CDV 12, donc à 0,40 % de carbone. Cet acier a subi la première séquence de nitruration ionique dans les conditions qui ont été précisées lors de la description du premier exemple.The second example relates to a chromium-molybdenum-vanadium steel of the type 40 CDV 12, therefore with 0.40% carbon. This steel underwent the first sequence of ionic nitriding under the conditions which were specified during the description of the first example.

L'échantillon d'acier 40 CDV 12 ainsi nitruré est introduit dans une caisse de cémentation où va se faire la deuxième phase du traitement, qui est une chromisation gazeuse. L'agent de cémentation est constitué par 99 % de ferrochrome à 65/70 % de chrome et 2 % de carbone dont la granulométrie moyenne est voisine de 2,7 mm (extrêmes : 0,5 et 4 mm) et 1 % de chlorure de magnésium, qui, lors de la montée en température, va se décomposer pour donner la vapeur active de chlorure de chrome CrC12.The 40 CDV 12 steel sample thus nitrided is introduced into a case hardening box where the second phase of the treatment will take place, which is a gas chromization. The cementing agent consists of 99% ferrochrome with 65/70% chromium and 2% carbon with an average particle size of around 2.7 mm (extremes: 0.5 and 4 mm) and 1% chloride of magnesium, which, when the temperature rises, will decompose to give the active vapor of chromium chloride CrC1 2 .

L'enceinte est portée à une température moyenne de 950°C pendant une durée de 15 heures et le traitement thermique ultérieur de la pièce d'acier est effectué immédiatement après la phase de chromisation.The enclosure is brought to an average temperature of 950 ° C for a period of 15 hours and the subsequent heat treatment of the steel part is carried out immediately after the chromization phase.

Dans ces conditions, on obtient une couche parfaitement monophasée de carbonitrures de chrome Cr2(C, N) dont l'épaisseur est voisine de 40 microns et dont les caractéristiques sont les mêmes que celles qui ont été décrites dans le premier exemple.Under these conditions, a perfectly single-phase layer of chromium carbonitrides Cr 2 (C, N) is obtained, the thickness of which is close to 40 microns and the characteristics of which are the same as those which were described in the first example.

Il est bien entendu que l'on peut, sans sortir du cadre de l'invention, imaginer des variantes et perfectionnements de détails, de même qu'envisager l'emploi de moyens équivalents.It is understood that it is possible, without departing from the scope of the invention, to imagine variants and refinements of details, as well as to envisage the use of equivalent means.

Claims (5)

1.- Perfectionnement à un procédé de chromisation des aciers constitué de trois traitements successifs : une nitruration ionique d'une couche superficielle d'épaisseur comprise entre 100 et 350 microns, réalisée dans une atmosphère constituée par un mélange d'azote et d'hydrogène, à une température comprise entre 450°C et 650°C, pendant une durée comprise entre 5 et 40 heures, de façon à obtenir entre 1,5 % et 2,5 % d'azote dans la couche nitrurée ; une chromisation gazeuse, d'une durée comprise entre 5 et 30 heures, et réalisée à des températures comprises entre 850 et 11000C ; un traitement thermique comprenant une trempe à l'huile de la pièce chromisée suivie d'un revenu à une température comprise entre 600° et 650°C, d'une durée comprise entre 30 minutes et 10 heures ; ledit perfectionnement étant caractérié en ce que, dans le traitement de chromisation gazeuse utilisant un cément à base de ferro-chrome à teneur en chrome comprise entre 50 % et 75 %, avec une granulométrie comprise entre 0,5 millimètre et 4 millimètres, on choisit un ferro-chrome dont la teneur en carbone est comprise entre 1 % et 3 %.1.- Improvement to a chromizing process for steels consisting of three successive treatments: ionic nitriding of a surface layer with a thickness between 100 and 350 microns, carried out in an atmosphere consisting of a mixture of nitrogen and hydrogen , at a temperature between 450 ° C and 650 ° C, for a period between 5 and 40 hours, so as to obtain between 1.5% and 2.5% of nitrogen in the nitrided layer; gas chromization, lasting between 5 and 30 hours, and carried out at temperatures between 850 and 1100 ° C .; a heat treatment comprising an oil quenching of the chromized part followed by tempering at a temperature between 600 ° and 650 ° C, lasting between 30 minutes and 10 hours; said improvement being characterized in that, in the gas chromization treatment using a cement based on ferro-chromium with chromium content between 50% and 75%, with a particle size between 0.5 millimeter and 4 millimeters, one chooses a ferro-chromium whose carbon content is between 1% and 3%. 2.- Perfectionnement selon la revendication 1, applicable aux aciers dont la teneur en carbone est comprise entre 0,20 % et 0,35 %, caractérisé en ce que le cément utilisé dans le traitement de chromisation gazau- se est constitué par un mélange pulvérulent d'une poudre de ferro-chrome présentant une teneur en chrome comprise entre 50 % et 75 %, une teneur en carbone comprise entre 1 % et 3 %, et une granulométrie comprise entre 0,5 millimètre et 4 millimètres, sans liant alumineux ni magnésien, et d'une poudre de chlorure d'ammonium, cette dernière poudre se trouvant dans ledit mélange pulvérulent à une concentration comprise entre 0,5 % et 1,5 %.2. Improvement according to claim 1, applicable to steels whose carbon content is between 0.20% and 0.35%, characterized in that the cement used in the gas chromium-plating treatment consists of a mixture pulverulent of a ferro-chromium powder having a chromium content of between 50% and 75%, a carbon content of between 1% and 3%, and a particle size of between 0.5 millimeter and 4 millimeters, without aluminous binder nor magnesium, and of an ammonium chloride powder, the latter powder being in said pulverulent mixture at a concentration of between 0.5% and 1.5%. 3.- Perfectionnement selon la revendication 1, applicable aux aciers dont la teneur en carbone est supérieure à 0,35 %, caractérisé en ce que le cément utilisé dans le traitement de chromisation gazeuse est constitué par un mélange pulvérulent d'une poudre de ferro-chrome présentant une teneur en chrome comprise entre 50 % et 75 %, une teneur en carbone comprise entre 1 % et 3 %, et une granulométrie comprise entre 0,5 millimètre et 4 millimètres, et d'une poudre de chlorure de magnésium, cette dernière poudre se trouvant dans ledit mélange pulvérulent à une concentration comprise entre 0,5 % et 1,5 %.3. Improvement according to claim 1, applicable to steels whose carbon content is greater than 0.35%, characterized in that the cement used in the gas chromization treatment consists of a pulverulent mixture of a ferro powder -chrome having a chromium content of between 50% and 75%, a carbon content of between 1% and 3%, and a particle size of between 0.5 millimeter and 4 millimeters, and of a magnesium chloride powder, the latter powder being in said pulverulent mixture at a concentration of between 0.5% and 1.5%. 4.- Perfectionnement selon la revendication 1, applicable aux aciers dont la teneur en carbone est supérieure à 0,35 %, caractérisé en ce que le cément utilisé dans le traitement de chromisation gazeuse est constitué par un mélange pulvérulent d'une poudre de ferro-chrome présentant une teneur en chrome comprise entre 50 % et 75 %, une teneur en carbone comprise entre 1 % et 3 %, et une granulométrie comprise entre 0,5 millimètre et 4 millimètres, et d'une poudre de fluorure d'ammonium, cette dernière poudre se trouvant dans ledit mélange pulvérulent à une concentration comprise entre 0,5 % et 1,5 %.4. Improvement according to claim 1, applicable to steels whose carbon content is greater than 0.35%, characterized in that the cement used in the gas chromization treatment is cons titrated by a pulverulent mixture of a ferro-chromium powder having a chromium content of between 50% and 75%, a carbon content of between 1% and 3%, and a particle size of between 0.5 millimeter and 4 millimeters , and an ammonium fluoride powder, the latter powder being in said pulverulent mixture at a concentration of between 0.5% and 1.5%. 5.- Perfectionnement selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le ferro-chrome utilisé dans le traitement de chromisation gazeuse présente une teneur en carbone de 2 %.5. Improvement according to any one of claims 1 to 4, characterized in that the ferro-chromium used in the gas chromization treatment has a carbon content of 2%.
EP81400804A 1980-05-29 1981-05-21 Method of gas-chromizing steels Expired EP0043742B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81400804T ATE6675T1 (en) 1980-05-29 1981-05-21 METHOD OF INCHROMING STEEL VIA THE GAS PHASE.

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FR8011950 1980-05-29
FR8011950A FR2483468A2 (en) 1980-05-29 1980-05-29 IMPROVEMENT IN THE CHROMIZATION OF STEELS BY GAS

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EP0043742A1 true EP0043742A1 (en) 1982-01-13
EP0043742B1 EP0043742B1 (en) 1984-03-14

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JP (1) JPS5719373A (en)
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DE (1) DE3162611D1 (en)
FR (1) FR2483468A2 (en)
ZA (1) ZA812835B (en)

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WO1986007614A1 (en) * 1985-06-17 1986-12-31 Kabushiki Kaisha Toyota Chuo Kenkyusho Method of treating the surface of iron alloy materials
WO2013075769A1 (en) 2011-11-22 2013-05-30 Märkisches Werk GmbH Process for producing a protective chromium layer

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JPS61291962A (en) * 1985-06-17 1986-12-22 Toyota Central Res & Dev Lab Inc Surface treatment of iron alloy material
GB2204327B (en) * 1987-05-01 1991-07-31 Nii Tekh Avtomobil Promy Deposition of diffusion carbide coatings on iron-carbon alloy articles
JPH0248397A (en) * 1988-08-09 1990-02-19 Kayaba Ind Co Ltd Autobalance type lifting gear
US6162513A (en) * 1996-04-19 2000-12-19 Korea Institute Of Science And Technology Method for modifying metal surface
US6209481B1 (en) 1996-08-30 2001-04-03 University Of Maryland Baltimore County Sequential ion implantation and deposition (SIID) system
JP4488840B2 (en) * 2004-08-30 2010-06-23 本田技研工業株式会社 Method for forming hard nitride layer, and roller chain and silent chain obtained by this method

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EP0010484A1 (en) * 1978-10-25 1980-04-30 Creusot-Loire Improvement in the chromising of steel in the gaseous phase

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US3249456A (en) * 1962-11-09 1966-05-03 Union Carbide Corp Diffusion coating process
US3282746A (en) * 1963-11-18 1966-11-01 Formsprag Co Method of hardening wear surfaces and product
DE2255997A1 (en) * 1971-11-16 1973-05-24 Toyoda Chuo Kenkyusho Kk PROCESS FOR INCHROMATING OBJECTS MADE OF IRON AND FERROUS ALLOYS
EP0010484A1 (en) * 1978-10-25 1980-04-30 Creusot-Loire Improvement in the chromising of steel in the gaseous phase

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986007614A1 (en) * 1985-06-17 1986-12-31 Kabushiki Kaisha Toyota Chuo Kenkyusho Method of treating the surface of iron alloy materials
WO2013075769A1 (en) 2011-11-22 2013-05-30 Märkisches Werk GmbH Process for producing a protective chromium layer

Also Published As

Publication number Publication date
ATE6675T1 (en) 1984-03-15
JPS5719373A (en) 1982-02-01
DE3162611D1 (en) 1984-04-19
FR2483468B2 (en) 1982-07-16
ZA812835B (en) 1982-04-28
JPS6145700B2 (en) 1986-10-09
EP0043742B1 (en) 1984-03-14
US4357182A (en) 1982-11-02
FR2483468A2 (en) 1981-12-04

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