EP0015813A1 - Process for boronizing articles made of metal or cermet, and articles provided with a boronized surface - Google Patents

Process for boronizing articles made of metal or cermet, and articles provided with a boronized surface Download PDF

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Publication number
EP0015813A1
EP0015813A1 EP80400252A EP80400252A EP0015813A1 EP 0015813 A1 EP0015813 A1 EP 0015813A1 EP 80400252 A EP80400252 A EP 80400252A EP 80400252 A EP80400252 A EP 80400252A EP 0015813 A1 EP0015813 A1 EP 0015813A1
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EP
European Patent Office
Prior art keywords
agent
parts
enclosure
gaseous
fluorinated
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EP80400252A
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German (de)
French (fr)
Inventor
François Henri Joannes Thevenot
Patrice Marie Victor Goeuriot
Julian Haworth Driver
Jean-Paul Raymond Lebrun
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NOUVELLE des Ets PARTIOT - SOFRATER Ste
Association pour la Recherche et le Developpement des Methodes et Processus Industriels
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NOUVELLE des Ets PARTIOT - SOFRATER Ste
Association pour la Recherche et le Developpement des Methodes et Processus Industriels
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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
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
    • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates
    • 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
    • C23C8/60—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 solids, e.g. powders, pastes
    • C23C8/62—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 solids, e.g. powders, pastes only one element being applied
    • C23C8/68—Boronising
    • 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
    • C23C8/60—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 solids, e.g. powders, pastes
    • C23C8/62—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 solids, e.g. powders, pastes only one element being applied
    • C23C8/68—Boronising
    • C23C8/70—Boronising of ferrous surfaces
    • 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
    • Y10T428/12965—Both containing 0.01-1.7% carbon [i.e., steel]
    • 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
    • Y10T428/12972—Containing 0.01-1.7% carbon [i.e., steel]
    • Y10T428/12979—Containing more than 10% nonferrous elements [e.g., high alloy, stainless]
    • 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
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
    • Y10T428/2495—Thickness [relative or absolute]
    • Y10T428/24967—Absolute thicknesses specified

Definitions

  • the subject of the invention is a process for treating parts of material from the group consisting of alloys of metals of the iron family (Fe, Ni, Co) and by cermets, in which the parts are brought to an operating temperature of of the order of 850 to 1150 ° C. in the presence of a solid boronizing agent and the boronization is activated by simultaneously subjecting the parts to the action of contact of the current of a gaseous fluorinated agent under operating conditions of pressure and temperature defined.
  • the subject of the invention is also a device for implementing the method and parts boronated on the surface.
  • the parts borided by this known process keep traces of powder stuck due to the appearance of a molten phase, so that they must be subjected to an additional treatment to remove the powder. more or less sintered, more or less adherent on their surface.
  • the activating agent which is consumed, being in the treatment bed, it must be regenerated, for example by quarters, with a new powder after each treatment operation.
  • the object of the invention is to propose a new very economical process and a new device making it possible to avoid the abovementioned drawbacks, in particular by obtaining a single-phase layer as regards carbon steels, and by obtaining clean parts without powder adhesion in all cases.
  • the gaseous fluorinated agent containing trifluorinated boroxole is produced by making pass the starting gas through a pulverulent mass of mineral oxides free of cationic impurities, such as simple or complex oxides of silicon, aluminum and magnesium, for example a silica sand, brought to a temperature at least equal to 450 ° C.
  • the agent introduced into the mass brought to at least 450 ° C. is boron trifluoride
  • the effluent will contain trifluorinated boroxole according to the reaction, in which MO is the simple or complex oxide.
  • the fluorinated agent is diluted in a neutral carrier gas.
  • the boriding agent can be, not only B 4 C l but any boron carbide B n C, in which n is between 4 and 10. It is also according to an advantageous characteristic of the invention that it will be possible to choose to enrich or deplete in B 10 the boron of the solid boronizing agent and / or of the gaseous fluorinating agent of activation or starting gas. In this way, it will be possible to obtain parts with more or less high effective cross section for neutron shutdown by enriching with B 10 with high effective cross section or with B 11 very transparent to neutrons.
  • the solid boronizing agent and the parts to be boronized are subjected to the contact action of the stream of gaseous fluorinated agent outside mutual contact.
  • This embodiment is decisive for enabling the production of clean parts free of more or less sintered powder. This embodiment therefore operates in the gas phase, as will be explained below, hence saving and ease of implementation.
  • the solid boriding agent present with the parts to be borided is interposed in the stream of the gaseous fluorinated agent upstream from the parts to be borided.
  • This embodiment will allow the parts to be borided to be placed directly in a treatment enclosure in order to expose them to the gaseous phase alone. treatment.
  • the solid boronizing agent and the parts to be boronized are out of mutual contact, it is however possible that the solid boronizing agent is arranged in the form of pulverulent solid material constituting treatment bed for the parts to be boronized, as it is known per se.
  • the invention also relates to the parts of carbon steels having undergone a boriding treatment on the surface to a thickness of about 20 to 200 ⁇ m covered with a single-phase layer of Fe 2 B crystals of acicular formation.
  • An installation according to the invention comprises a reactor 1 made of refractory steel.
  • a reactor 1 made of refractory steel.
  • the bottom enclosure 3 is intended to contain the parts to be boronized 6.
  • L the upper enclosure 2 is intended to contain a pulverulent mass of mineral oxides 7.
  • the reactor 1 is in an oven 8, the temperature of which is regulated, in a manner known per se, by means of a thermocouple 9.
  • a pipe 10, controlled by a valve 11 is inserted into the upper wall of the reactor 1, so as to open into the enclosure 2.
  • the enclosure 3 and the reactor 1 are closed, at the bottom, by porous parcels, respectively 12 and 13, the porous wall 13 being closed, on its other face, by a pipe 14 for discharging gaseous effluents.
  • the valve 11 is connected, for the supply of gas, to two gaseous sources, respectively a source 15 of compressed boron trifluoride and a source 16 of diluent inert gas, such as argon or nitrogen. These two sources 15 and 16 are connected to the valve 11 through two flow meters 17 and 18 discharging on a pipe com mune 19.
  • the pipe 14 arrives on a valve 20 connected to a pressure gauge 21 and to a washer assembly 22 by a pipe 23.
  • a distribution valve 25 between a pipe d discharge 26 and a recycling pipe 27, which brings part of the gas effluent to valve 11, which is then a mixing valve.
  • the lower enclosure 3 In the embodiment of FIG. 1, provision has been made for the lower enclosure 3 to contain the boriding agent 5 in the form of a bed coating the parts, as is known per se. But according to the embodiment of Figure 2, the lower enclosure 3 does not contain any powdery or granular bed. In this case, the parts 6 and the solid boronizing agent are separated from each other, the agent is arranged in the form of sintered elements 30 suspended in the lower enclosure 3.
  • the preferred embodiment is that of Figures 3 and 4 which differs from the previous one, by the presence of a retaining grid 31 disposed in the upper part of the lower enclosure 3 for an interposed bed solid borating agent 33 in powder form with a particle size of 1 to 2 ⁇ m on the path of the gaseous activating agent supplied through the powdery mass of mineral oxides 7.
  • the embodiment of FIG. 3 is suitable for small parts which can be coated with powdered silicon carbide 34, as an inert agent.
  • FIG. 4 we simply omitted to place the bed of silicon carbide to deposit the part or parts 6 directly in the enclosure 3.
  • a boronizing agent of known type consisting of a powder of B 4 C at a particle size of 1 to 100 ⁇ m mixed with a powder of silicon carbide of 100 has been placed in enclosure 3. ⁇ m in mass proportion from 2/98 to 100/0.
  • enclosure 2 we put a pure silica sand washed with acids 90% of which passes through a 2 mm sieve.
  • the enclosure is scanned with a neutral gas, nitrogen or argon, at the same time as the temperature is raised.
  • the BF 3 gas possibly diluted, is sent when the temperature reaches approximately 500 to 950 ° C. The latter is chosen as the boronization temperature.
  • the duration of the passage of the activating gas varies from half to the entire time this stay of the parts at 950 ° C., said residence time having been approximately 5 hours. Simultaneously, the temperature of the silica bed 7 was brought to about 850 ° C.
  • FIG. 1 the installation of FIG. 1 was modified as shown in FIGS. 2, 3 and 4.
  • Example 3 In the embodiment of FIG. 2, a piece of carbon steel 6 was placed in the presence, but without contact, of hot sintered pieces 30 made of ⁇ boron, B 4 C and B 10 C. We sent BF 3 through the sand bed 7 of enclosure 2 for 18 h while maintaining the temperature of enclosure 3 at 1000 ° C. FIG. 7 shows a micrographic section of the steel thus borided.
  • Example 4 In the embodiment of FIG. 3, two parts, one made of carbon steel, the other of chromium-nickel 18/10, were placed in the SiC bed of enclosure 3. BF 3 was surrounded by the sand bed 7 of enclosure 2 for 2.5 h while maintaining the temperature of enclosure 3 at 1020 ° C.
  • FIG. 8 shows a micrographic section of the carbon steel thus boronized and in FIG. 9 a section of the chrome-nickel steel thus boronized.
  • FIG. 10 shows a micrographic section of the external surface of the workpiece and in FIG. 11 a micrographic section of the surface of the notch with a saw.
  • FIG. 7 shows the appearance of the borated layer obtained in the case of the reactor of Example 3.
  • the progression of the dendrites is not perpendicular to the surface but has been disturbed by the presence of a phase which appears as perlite after cooling.
  • the boronization speed therefore has an important influence on the progression of the boronized layer in the matrix and the growth direction [001] is not absolute.
  • this part is boronised (FIGS. 10 and 11), not only on the two external faces (90 to 120 ⁇ m), but also on the internal faces defined by the saw cuts.
  • a micrograph of these internal faces shows a borated layer of variable thickness and of discontinuous acicular character which is explained by the only intervention of a gas phase.
  • the invention has made it possible to develop an original process making it possible to boron all steels up to tool steels with total reliability.
  • the previous processes led to poor quality parts on mild steels (formation of two layers FeB + Fe 2 B), the flexibility of the process of the invention combined with the use of an activation moderator (Si0 2 ) allows, including in industrial conditions, to produce parts of consistent and satisfactory quality.
  • Mechanical tests have shown that the behavior of the layers obtained on tool steel was of very good quality.
  • boronization of stainless steel to chromium-nickel 18.10 remains of weak effect.
  • durations, percentages and particle sizes given in the previous description are not limiting. They can be varied as a function of the desired greater or lesser speed of formation and thickness of the layer. Some of these factors have only a slight influence, such as, for example, the particle size of B 4 C and of SiC.
  • boron carbides other than B 4 C such as borides B n C, in which n is between 4 and 10.
  • the main phase detected by X-ray diffraction is CoB; the mixed boride W 2 CoB 2 also seems to be present, on the other hand W 2 B 5 is absent.
  • W-Co mixed borides
  • FIG 12 there is shown a particularly simple embodiment of a reactor for implementing the method of the invention.
  • the lower part of the reactor constitutes the enclosure 3 closed by a watertight cover 40 with seal 41 cooled with water.
  • the enclosure 2 is produced in the form of a container which can be fitted into the reactor before fitting the cover 40.
  • the bottom of the enclosure 2 comprises the grid 4 for retaining the sand and letting the activation gas pass and a grid 31 for retain boron carbide, preferably powdery.
  • a pipe 10 fixed to the enclosure 2 crosses the cover to bring BF 3 through the sand of the enclosure2.
  • the cover is crossed by a central chimney 14 which also crosses, in a sealed manner, the enclosure 2 to end near the bottom of the reactor under a grid 12 for retaining the parts to be borided.
  • the temperature probe 9 can be placed in the chimney 14.

Abstract

L'invention concerne un procédé et un dispositif de boruration de pièces en métal ou cermet et des pièces boturées en surface. On dispose les pièces dans une enceinte 3 entre 850 et 1150°C et on les soumet, en présence de carbure de bore, à un courant gazeux de boroxole trifluoré (BOF)3. Le carbure de bore est avantageusement pulvérulent et hors de contact des pièces à borurer.The invention relates to a method and a device for boriding metal or cermet parts and parts botured on the surface. The parts are placed in an enclosure 3 between 850 and 1150 ° C. and they are subjected, in the presence of boron carbide, to a gas stream of trifluorinated boroxole (BOF) 3. Boron carbide is advantageously powdery and out of contact with the parts to be borided.

Description

L'invention a pour objet un procédé de traitement de pièces en matériau du groupe constitué par les alliages de métaux de la famille du fer (Fe, Ni, Co) et par les cermets, dans lequel on porte les pièces à une température opératoire de l'ordre de 850 à 1150°C en présence d'un agent borurant solide et on active la boruration en soumettant simultanément les pièces à l'action de contact du courant d'un agent fluoré gazeux dans des conditions opératoires de pression et de température définies. L'invention a également pour objet un dispositif pour la mise en oeuvre du procédé et des pièces borurées en surface.The subject of the invention is a process for treating parts of material from the group consisting of alloys of metals of the iron family (Fe, Ni, Co) and by cermets, in which the parts are brought to an operating temperature of of the order of 850 to 1150 ° C. in the presence of a solid boronizing agent and the boronization is activated by simultaneously subjecting the parts to the action of contact of the current of a gaseous fluorinated agent under operating conditions of pressure and temperature defined. The subject of the invention is also a device for implementing the method and parts boronated on the surface.

On connaît par le brevet français N° 2 018 609 et son équivalent U.S. 3 673 005, un procédé du type rappelé ci-dessus pour la boruration des aciers, dans lequel l'activateur est un fluoroborate mélangé à l'agent borurant en présence de borax et éventuellement additionné d'un agent diluant constitué par de l'alumine. Toute la réaction se passe en phase solide et permet d'obtenir un revêtement dans lequel on observe deux phases, l'une de FeB, l'autre de Fe2B. Mais les structures cristallines différentes de ces deux phases créent'des tensions nuisibles à la bonne tenue au refroidissement, d'autant plus que la phase FeB est plus fragile, d'où risques d'écaillage du revêtement. On observe, d'autre part, que les pièces borurées par ce procédé connu gardent des traces de poudre collée du fait de l'apparition d'une phase fondue, si bien qu'il faut leur faire subir un traitement supplémentaire pour éliminer la poudre plus ou moins frittée, plus ou moins adhérente sur leur surface. En outre l'agent activateur, qui est consommé, se trouvant dans le lit de traitement, il faut régénérer celui-ci, par exemple par quarts, avec une poudre neuve après chaque opération de traitement.We know from French Patent No. 2,018,609 and its equivalent US 3,673,005, a process of the type mentioned above for the boriding of steels, in which the activator is a fluoroborate mixed with the boriding agent in the presence of borax and optionally added with a diluting agent consisting of alumina. The whole reaction takes place in the solid phase and makes it possible to obtain a coating in which two phases are observed, one of FeB, the other of Fe 2 B. But the different crystal structures of these two phases create harmful tensions. good resistance to cooling, especially since the FeB phase is more fragile, hence the risk of chipping of the coating. It is observed, on the other hand, that the parts borided by this known process keep traces of powder stuck due to the appearance of a molten phase, so that they must be subjected to an additional treatment to remove the powder. more or less sintered, more or less adherent on their surface. In addition, the activating agent, which is consumed, being in the treatment bed, it must be regenerated, for example by quarters, with a new powder after each treatment operation.

On sait, par ailleurs, que le même procédé est applicable avec les mêmes avantages et inconvénients aux cermets, notamment au carbure de tungstène ou de titane pris dans une matrice de cobalt. On se reportera, par exemple à l'article G.L. ZHUNKOVSKII et al. Boronizing of cobalt and some cobalt base alloys. Soviet powder metal- lurgy - 11, (1972) p. 888-90, et à l'article O. KNOTEK et al. Surface layers on cobalt base alloys by boron diffusion. Thin solid films, 45 (1977) p. 331-9.It is known, moreover, that the same process is applicable with the same advantages and disadvantages to cermets, in particular to tungsten carbide or titanium taken from a cobalt matrix. Reference is made, for example, to the article GL ZHUNKOVSKII et al. Boronizing of cobalt and some cobalt base alloys. Soviet powder metal- lurgy - 11, (1972) p. 888-90, and in article O. KNOTEK et al. Surface layers on cobalt base alloys by boron diffusion. Thin solid films, 45 (1977) p. 331-9.

Le but de l'invention est de proposer un nouveau procédé très économique et un nouveau dispositif permettant d'éviter les inconvénients précités, notamment par obtention d'une couche monophasée en ce qui concerne les aciers au carbone, et par obtention de pièces propres sans adhésion de poudre dans tous les cas.The object of the invention is to propose a new very economical process and a new device making it possible to avoid the abovementioned drawbacks, in particular by obtaining a single-phase layer as regards carbon steels, and by obtaining clean parts without powder adhesion in all cases.

Ces buts sont atteints, selon l'invention, par un procédé du type décrit au début, grâce au fait que l'agent fluoré gazeux contient du boroxole trifluoré (BOF)3. Cet agent d'activation présente de nombreux avantages qui apparaîtront plus loin.These aims are achieved, according to the invention, by a process of the type described at the start, thanks to the fact that the gaseous fluorinated agent contains trifluorinated boroxole (BOF) 3 . This activating agent has many advantages which will appear below.

Selon l'invention, il est avantageux d'utiliser comme gaz de départ le trifluorure de bore BF3 ou un mélange gazeux contenant BF3 et, selon un mode de réalisation préféré, on produit l'agent fluoré gazeux contenant du boroxole trifluoré en faisant passer le gaz de départ à travers une masse pulvérulente d'oxydes minéraux exempts d'impuretés cationiques, tels qu'oxydes simples ou complexes de silicium, d'aluminium et de magnésium, par exemple un sable de silice, portée à une température au moins égale à 450°C.According to the invention, it is advantageous to use as starting gas boron trifluoride BF 3 or a gas mixture containing BF 3 and, according to a preferred embodiment, the gaseous fluorinated agent containing trifluorinated boroxole is produced by making pass the starting gas through a pulverulent mass of mineral oxides free of cationic impurities, such as simple or complex oxides of silicon, aluminum and magnesium, for example a silica sand, brought to a temperature at least equal to 450 ° C.

De cette façon, il n'y a plus d'inconvénients dus à la consommation interne de l'agent d'activation, puisque celui-ci est amené de l'extérieur. De cette façon, également, et selon la vitesse de passage de l'agent fluoré d'activation à travers la masse pulvérulente d'oxydes, on observe une modération de l'action de l'agent gazeux effluent de ladite masse. Si, comme ce sera le plus économique selon l'invention, l'agent introduit dans la masse portée à au moins 450°C est le trifluorure de bore, l'effluent contiendra du boroxole trifluoré selon la réaction,

Figure imgb0001
dans laquelle MO est l'oxyde simple ou complexe.In this way, there are no more disadvantages due to the internal consumption of the activating agent, since it is brought from the outside. In this way, too, and depending on the speed of passage of the fluorinated activating agent through the pulverulent mass of oxides, a moderation of the action of the effluent gaseous agent of said mass is observed. If, as will be the most economical according to the invention, the agent introduced into the mass brought to at least 450 ° C. is boron trifluoride, the effluent will contain trifluorinated boroxole according to the reaction,
Figure imgb0001
 in which MO is the simple or complex oxide.

Dans tous les cas, c'est une grande simplification selon l'invention de séparer l'agent borurant fort peu consommé, un agent modérateur également fort peu consommé et l'agent activateur.In all cases, it is a great simplification according to the invention to separate the borating agent which is very little consumed, a moderating agent also very little consumed and the activating agent.

Il est avantageux d'amener à débit réglable, et de préférence à une pression voisine de la pression atmosphérique, l'agent fluoré d'activation au contact des pièces à borurer.It is advantageous to bring the fluorinated activating agent at adjustable pressure, and preferably at a pressure close to atmospheric pressure, in contact with the parts to be borided.

Selon un mode de réalisation, l'agent fluoré est dilué dans un gaz vecteur neutre.According to one embodiment, the fluorinated agent is diluted in a neutral carrier gas.

Selon un mode de réalisation, l'agent borurant peut être, non seulement B4Cl mais tout carbure de bore BnC, dans lequel n est compris entre 4 et 10. C'est également selon une caractéristique avantageuse de l'invention qu'on pourra choisir d'enrichir ou appauvrir en B10 le bore de l'agent borurant solide et/ou de l'agent fluoré gazeux d'activation ou gaz de départ. De cette façon on pourra obtenir des pièces à plus ou moins forte section efficace réglée d'arrêt des neutrons en enrichissant en B10 à forte section efficace ou en B11 très transparent aux neutrons.According to one embodiment, the boriding agent can be, not only B 4 C l but any boron carbide B n C, in which n is between 4 and 10. It is also according to an advantageous characteristic of the invention that it will be possible to choose to enrich or deplete in B 10 the boron of the solid boronizing agent and / or of the gaseous fluorinating agent of activation or starting gas. In this way, it will be possible to obtain parts with more or less high effective cross section for neutron shutdown by enriching with B 10 with high effective cross section or with B 11 very transparent to neutrons.

Selon un mode de réalisation préféré de l'invention, l'agent borurant solide et les pièces à borurer sont soumis à l'action de contact du courant d'agent fluoré gazeux hors de contact mutuel. Ce mode de réalisation est déterminant pour permettre l'obtention de pièces propres exemptes de poudre plus ou moins frittée. Ce mode de réalisation opère donc en phase gazeuse, comme il sera exposé plus loin, d'où économie et facilité de mise en oeuvre.According to a preferred embodiment of the invention, the solid boronizing agent and the parts to be boronized are subjected to the contact action of the stream of gaseous fluorinated agent outside mutual contact. This embodiment is decisive for enabling the production of clean parts free of more or less sintered powder. This embodiment therefore operates in the gas phase, as will be explained below, hence saving and ease of implementation.

A cet effet, il est avantageux que l'agent borurant solide présent avec les pièces à borurer soit interposé dans le courant de l'agent fluoré gazeux en amont des pièces à borurer. Ce mode de réalisation permettra de disposer directement dans une enceinte de traitement les pièces à borurer pour les y exposer à la seule phase gazeuse de traitement. Mais, pour les très petites pièces, on pourra les disposer cependant dans un lit constitué par une masse inerte granuleuse ou pulvérulente, telle que le carbure de silicium.To this end, it is advantageous that the solid boriding agent present with the parts to be borided is interposed in the stream of the gaseous fluorinated agent upstream from the parts to be borided. This embodiment will allow the parts to be borided to be placed directly in a treatment enclosure in order to expose them to the gaseous phase alone. treatment. However, for very small parts, they can however be placed in a bed constituted by a granular or powdery inert mass, such as silicon carbide.

Bien que, selon le mode de réalisation préféré, l'agent borurant solide et les pièces à borurer soient hors de contact mutuel, il est cependant possible que l'agent borurant solide soit disposé sous forme de matière solide pulvérulente constituant lit de traitement pour les pièces à borurer, comme il est connu en soi.Although, according to the preferred embodiment, the solid boronizing agent and the parts to be boronized are out of mutual contact, it is however possible that the solid boronizing agent is arranged in the form of pulverulent solid material constituting treatment bed for the parts to be boronized, as it is known per se.

Il est avantageux de recycler, au moins partiellement, l'agent fluoré gazeux d'activation.It is advantageous to recycle, at least partially, the gaseous fluorinating activating agent.

Un dispositif particulièrement approprié pour la mise en oeuvre de l'invention comporte :

  • - une première enceinte de traitement de boruration,
  • - des moyens de chauffage de ladite première enceinte à une température de l'ordre de 850 à 1150°C,
  • - une seconde enceinte pour une masse pulvérulente ou granuleuse d'oxydes minéraux,
  • - des moyens de chauffage de ladite seconde enceinte à au moins 450°C environ,
  • - des moyens d'amenée d'un gaz fluoré dans ladite seconde enceinte,
  • - un passage de transfert de l'effluent gazeux fluoré de la seconde enceinte à la première enceinte,
  • - des moyens d'évacuation de l'effluent gazeux fluoré de ladite première enceinte.
A device particularly suitable for implementing the invention comprises:
  • - a first boronization treatment enclosure,
  • means for heating said first enclosure to a temperature of the order of 850 to 1150 ° C,
  • - a second enclosure for a powdery or granular mass of mineral oxides,
  • means for heating said second enclosure to at least approximately 450 ° C.,
  • means for supplying a fluorinated gas into said second enclosure,
  • a passage for the transfer of the fluorinated gaseous effluent from the second enclosure to the first enclosure,
  • - means for discharging the fluorinated gaseous effluent from said first enclosure.

L'invention concerne également les pièces d'aciers au carbone ayant subi en surface un traitement de boruration sur une épaisseur d'environ 20 à 200 pm recouvertes d'une couche monophasée de cristaux de Fe2B de formation aciculaire.The invention also relates to the parts of carbon steels having undergone a boriding treatment on the surface to a thickness of about 20 to 200 μm covered with a single-phase layer of Fe 2 B crystals of acicular formation.

D'autres caractéristiques et avantages ressortiront de la description, qui sera donnée ci-après, uniquement à titre d'exemples, de modes de réalisation de l'invention. On se reportera à cet effet aux dessins et micrographies annexés, dans lesquels :

  • - La figure 1 est un schéma d'ensemble d'une installation selon l'invention pour la mise en oeuvre du procédé selon l'invention,
  • - les figures 2, 3 et 4 sont des coupes partielles à plus grande échelle, de la partie du réacteur de la figure 1 contenant les deux enceintes décrites plus loin,
  • - les figures 5 à 11 sont des coupes micrographiques d'aciers borurés par le procédé de l'invention,
  • - la figure 12 est une vue en coupe, à plus grande échelle, d'une variante pour le réacteur compris dans le schéma de la figure 1.
Other characteristics and advantages will emerge from the description, which will be given below, only by way of examples, of embodiments of the invention. For this purpose, reference is made to the drawings and attached micrographs, in which:
  • FIG. 1 is an overall diagram of an installation according to the invention for implementing the method according to the invention,
  • FIGS. 2, 3 and 4 are partial sections on a larger scale, of the part of the reactor of FIG. 1 containing the two enclosures described below,
  • FIGS. 5 to 11 are micrographic sections of boron steels by the process of the invention,
  • FIG. 12 is a sectional view, on a larger scale, of a variant for the reactor included in the diagram of FIG. 1.

Une installation selon l'invention comprend un réacteur 1 en acier réfractaire. Dans ce réacteur sont disposés, du haut vers le bas, deux enceintes 2 et 3 simplement séparées par une grille de retenue 4 disposée au fond de l'enceinte 2. L'enceinte inférieure 3 est destinée à contenir les pièces à borurer 6. L'enceinte supérieure 2 est destinée à contenir une masse pulvérulente d'oxydes minéraux 7. Le réacteur 1 est dans un four 8 dont la température est régulée, de façon connue en soi, grâce à un thermocouple 9.An installation according to the invention comprises a reactor 1 made of refractory steel. In this reactor are arranged, from top to bottom, two enclosures 2 and 3 simply separated by a retaining grid 4 disposed at the bottom of the enclosure 2. The bottom enclosure 3 is intended to contain the parts to be boronized 6. L the upper enclosure 2 is intended to contain a pulverulent mass of mineral oxides 7. The reactor 1 is in an oven 8, the temperature of which is regulated, in a manner known per se, by means of a thermocouple 9.

Une canalisation 10, commandée par une vanne 11 est piquée dans la paroi supérieure du réacteur 1, de façon à déboucher dans l'enceinte 2. L'enceinte 3 et le réacteur 1 sont fermés, en bas, par des parcis poreuses, respectivement 12 et 13, la paroi poreuse 13 étant fermée, sur son autre face, par une canalisation 14 d'évacuation des effluents gazeux.A pipe 10, controlled by a valve 11 is inserted into the upper wall of the reactor 1, so as to open into the enclosure 2. The enclosure 3 and the reactor 1 are closed, at the bottom, by porous parcels, respectively 12 and 13, the porous wall 13 being closed, on its other face, by a pipe 14 for discharging gaseous effluents.

La vanne 11 est raccordée, pour l'alimentation en gaz, à deux sources gazeuses, respectivement une source 15 de trifluorure de bore comprimé et une source 16 de gaz inerte diluant, tel qu'argon ou azote. Ces deux sources 15 et 16 sont raccordées à la vanne 11 à travers deux débimètres 17 et 18 débitant sur une canalisation commune 19.The valve 11 is connected, for the supply of gas, to two gaseous sources, respectively a source 15 of compressed boron trifluoride and a source 16 of diluent inert gas, such as argon or nitrogen. These two sources 15 and 16 are connected to the valve 11 through two flow meters 17 and 18 discharging on a pipe com mune 19.

De son côté la canalisation 14 arrive sur une vanne 20 raccordée à un manomètre 21 et à un ensemble laveur 22 par une canalisation 23. A la sortie de la canalisation 24, il est possible d'ajouter une vanne de répartition 25 entre une canalisation d'évacuation 26 et une canalisation de recyclage 27, qui ramène une partie de l'effluent gaz à la vanne 11, qui est alors une vanne mélangeuse.For its part, the pipe 14 arrives on a valve 20 connected to a pressure gauge 21 and to a washer assembly 22 by a pipe 23. At the outlet of the pipe 24, it is possible to add a distribution valve 25 between a pipe d discharge 26 and a recycling pipe 27, which brings part of the gas effluent to valve 11, which is then a mixing valve.

Dans le mode de réalisation de la figure 1, on a prévu que l'enceinte inférieure 3 devrait contenir l'agent borurant 5 sous forme de lit enrobant les pièces, comme il est connu en soi. Mais selon le mode de réalisation de la figure 2, l'enceinte inférieure 3 ne contient aucun lit pulvérulent ou granuleux. Dans ce cas les pièces 6 et l'agent borurant solide sont séparés l'un de l'autre, l'agent est disposé sous forme d'éléments frittés 30 suspendus dans l'enceinte inférieure 3.In the embodiment of FIG. 1, provision has been made for the lower enclosure 3 to contain the boriding agent 5 in the form of a bed coating the parts, as is known per se. But according to the embodiment of Figure 2, the lower enclosure 3 does not contain any powdery or granular bed. In this case, the parts 6 and the solid boronizing agent are separated from each other, the agent is arranged in the form of sintered elements 30 suspended in the lower enclosure 3.

Mais, selon l'invention, le mode de réalisation préféré est celui des figures 3 et 4 qui diffère de la précédente, par la présence d'une grille de retenue 31 disposée dans la partie supérieure de l'enceinte inférieure 3 pour un lit interposé d'agent borurant solide 33 pulvérulent à la granulométrie de 1 à 2 µm sur le trajet de l'agent gazeux d'activation amené à travers la masse pulvérulente d'oxydes minéraux 7. Le mode de réalisation de la figure 3 convient pour les petites pièces qu'on peut enrober de carbure de silicium pulvérulent 34, comme agent inerte. A la figure 4, on a tout simplement omis de placer le lit de carbure de silicium pour déposer la ou les pièces 6 directement dans l'enceinte 3.But, according to the invention, the preferred embodiment is that of Figures 3 and 4 which differs from the previous one, by the presence of a retaining grid 31 disposed in the upper part of the lower enclosure 3 for an interposed bed solid borating agent 33 in powder form with a particle size of 1 to 2 μm on the path of the gaseous activating agent supplied through the powdery mass of mineral oxides 7. The embodiment of FIG. 3 is suitable for small parts which can be coated with powdered silicon carbide 34, as an inert agent. In FIG. 4, we simply omitted to place the bed of silicon carbide to deposit the part or parts 6 directly in the enclosure 3.

Dans l'installation de la figure 1 on a disposé, dans l'enceinte 3, un agent borurant de type connu consistant en une poudre de B4C à une granulométrie de 1 à 100 µm mélangée avec une poudre de carbure de silicium de 100 µm en proportion massique de 2/98 à 100/0. Dans l'enceinte 2 on a mis un sable de silice pure lavé aux acides dont 90% passent au tamis de 2 mm. Après avoir mis des pièces à traiter dans le lit de l'enceinte 3, on balaye l'enceinte avec un gaz neutre, azote ou argon, en même temps qu'on élève la température. Puis on envoie le gaz BF3, éventuellement dilué, lorsque la température atteint 500 à 950°C environ. Cette dernière est choisie comme température de boruration. La durée du passage du gaz activateur varie de la moitié à la totalité du temps ce séjour des pièces à 950°C, ledit temps de séjour ayant été d'environ 5 heures. Simultanément, la température du lit 7 de silice était portée à environ 850°C.In the installation of FIG. 1, a boronizing agent of known type consisting of a powder of B 4 C at a particle size of 1 to 100 μm mixed with a powder of silicon carbide of 100 has been placed in enclosure 3. µm in mass proportion from 2/98 to 100/0. In enclosure 2 we put a pure silica sand washed with acids 90% of which passes through a 2 mm sieve. After placing the parts to be treated in the bed of enclosure 3, the enclosure is scanned with a neutral gas, nitrogen or argon, at the same time as the temperature is raised. Then the BF 3 gas, possibly diluted, is sent when the temperature reaches approximately 500 to 950 ° C. The latter is chosen as the boronization temperature. The duration of the passage of the activating gas varies from half to the entire time this stay of the parts at 950 ° C., said residence time having been approximately 5 hours. Simultaneously, the temperature of the silica bed 7 was brought to about 850 ° C.

Exemples 1 et 2 Il a été essayé avec une proportion massique B4C/SiC de 20/80 deux aciers au carbone à 0,1% et 0,35% respectivement désignés, XC 10 et XC 35, selon désignation AFNOR. Après refroidissement, les pièces ont été examinées en laboratoire.Examples 1 and 2 It was tested with a mass proportion B 4 C / SiC of 20/80 two carbon steels at 0.1% and 0.35% respectively designated, XC 10 and XC 35, according to AFNOR designation. After cooling, the parts were examined in the laboratory.

On a pu constater (voir les coupes micrographiques aux figures 5 et 6) que, dans les deux cas, les pièces étaient recouvertes d'une couche A monophasée de 170 µm de cristaux de Fe2B orientés avec formation de dents pénétrant bien dans le métal C en y constituant une formation aciculaire. Une couche B de 10 µm seulement de cristaux de FeB/Fe2B non orientés recouvrait la couche de Fe2B et n'était donc pas de nature à y provoquer des tensions nuisibles, puisque, comme dans les procédés connus, cette couche peut être éliminée par simple sablage au jet, ou même conservée telle quelle comme s'éliminant à l'usage si on peut accepter des pièces à aspect mat.We could see (see the micrographic sections in Figures 5 and 6) that, in both cases, the parts were covered with a single-phase layer A of 170 µm of Fe 2 B crystals oriented with formation of teeth penetrating well into the metal C by constituting an acicular formation there. A layer B of only 10 μm of undirected FeB / Fe 2 B crystals covered the layer of Fe 2 B and was therefore not likely to cause harmful tensions therein, since, as in the known processes, this layer can be eliminated by simple sandblasting, or even preserved as such as being eliminated in use if we can accept parts with a mat appearance.

On a obtenu ainsi des couches utiles de 170 µm, pratiquement monophasées, alors qu'avec le procédé connu, toutes choses égales par ailleurs, on a obtenu des couches de 200 µm mais biphasées avec deux couches de phases différentes fortement orientées de FeB et Fe2B dans une proportion 1/2 à 1/3.We thus obtained useful layers of 170 μm, practically single-phase, whereas with the known process, all other things being equal, we obtained layers of 200 μm but two-phase with two layers of different strongly oriented phases of FeB and Fe 2 B in a proportion 1/2 to 1/3.

On a ensuite procédé, selon le mode de réalisation préféré de l'invention en modifiant l'installation de la figure 1 comme représenté aux figures 2, 3 et 4.Then, according to the preferred embodiment of the invention, the installation of FIG. 1 was modified as shown in FIGS. 2, 3 and 4.

Exemple 3 Dans le mode de réalisation de la figure 2, on a disposé une pièce en acier au carbone 6 en présence, mais hors contact, de pièces frittées à chaud 30 en bore β, B4C et B10C. On a envoyé BF3 à travers le lit de sable 7 de l'enceinte 2 pendant 18 h en maintenant la température de l'enceinte 3 à 1000°C. On a représenté à la figure 7 une coupe micrographique de l'acier ainsi boruré.Example 3 In the embodiment of FIG. 2, a piece of carbon steel 6 was placed in the presence, but without contact, of hot sintered pieces 30 made of β boron, B 4 C and B 10 C. We sent BF 3 through the sand bed 7 of enclosure 2 for 18 h while maintaining the temperature of enclosure 3 at 1000 ° C. FIG. 7 shows a micrographic section of the steel thus borided.

Exemple 4 Dans le mode de réalisation de la figure 3, on a disposé dans le lit 34 de SiC de l'enceinte 3 deux pièces, l'une en acier au carbone, l'autre au chrome-nickel 18/10. On a envcyé BF3 à travers le lit de sable 7 de l'enceinte 2 pendant 2,5h en maintenant la température de l'enceinte 3 à 1020°C. On a représenté à la figure 8 une coupe micrographique de l'acier au carbone ainsi boruré et à la figure 9 une coupe de l'acier au chrome-nickel ainsi boruré.Example 4 In the embodiment of FIG. 3, two parts, one made of carbon steel, the other of chromium-nickel 18/10, were placed in the SiC bed of enclosure 3. BF 3 was surrounded by the sand bed 7 of enclosure 2 for 2.5 h while maintaining the temperature of enclosure 3 at 1020 ° C. FIG. 8 shows a micrographic section of the carbon steel thus boronized and in FIG. 9 a section of the chrome-nickel steel thus boronized.

Exemples 5 et 6 Dans le mode de réalisation de la figure 4, or a traité une pièce 6 en acier au carbone ayant reçu deux traits de scie de 0,5 mm sur sa tranche. On a envoyé BF3 à travers le lit de sable 7 de l'enceinte 2 pendant 2 h à 1000°C. On a représenté à la figure 10 une coupe micrographique de la surface extérieure de la pièce et à la figure 11 une coupe micrographique de la surface de l'entaille à la scie.Examples 5 and 6 In the embodiment of FIG. 4, gold treated a piece 6 of carbon steel having received two saw cuts of 0.5 mm on its edge. BF 3 was sent through the sand bed 7 of enclosure 2 for 2 h at 1000 ° C. FIG. 10 shows a micrographic section of the external surface of the workpiece and in FIG. 11 a micrographic section of the surface of the notch with a saw.

Chacune de ces opérations a conduit à la boruration des pièces en aciers présentes dans le réac- teur. L'épaisseur de la couche compacte (Fe2B seul) est assez faible dans le cas du procédé de l'exemple 3, 15 à 20 µm environ. L'étude métallographique des pièces ainsi traitées renseigne sur la morphologie de ces couches. Pour le cas du procédé de l'exemple 4 elles sont identiques à celles déjà observées aux exemples 1 et 2. La couche n'est pas plate à proprement dire (figure 9), on note l'arrêt de la boruration à certains joints de grains lorsque ceux-ci sont parallèles à la surface ou offrent un angle allant jusqu'à 120° environ avec celle-ci. La figure 7 montre l'aspect de la couche borurée obtenue dans le cas du réacteur de l'exemple 3. La progression des dendrites ne se fait pas perpendiculairement à la surface mais a été perturbée par la présence d'une phase qui apparaît comme de la perlite après refroidissement. La vitesse de boruration a donc une influence importante sur la progression de la couche borurée dans la matrice et la direction de croissance [001] n'est pas absolue.Each of these operations led to the boriding of the steel parts present in the reactor. The thickness of the compact layer (Fe 2 B alone) is fairly small in the case of the method of Example 3, 15 to 20 μm approximately. The metallographic study of the parts thus treated provides information on the morphology of these layers. In the case of the method of Example 4, they are identical to those already observed in Examples 1 and 2. The layer is not actually flat (FIG. 9), note the stopping of boriding at certain joints of grains when these are parallel to the surface or have an angle of up to about 120 ° with it. FIG. 7 shows the appearance of the borated layer obtained in the case of the reactor of Example 3. The progression of the dendrites is not perpendicular to the surface but has been disturbed by the presence of a phase which appears as perlite after cooling. The boronization speed therefore has an important influence on the progression of the boronized layer in the matrix and the growth direction [001] is not absolute.

En ce qui concerne la pièce ayant reçu des traits de scie, on constate que cette pièce est borurée (figures 10 et 11), non seulement sur les deux faces externes (90 à 120 µm), mais aussi sur les faces internes définies par les traits de scie. Une micrographie de ces faces internes montre une couche borurée d'épaisseur variable et de caractère aciculaire discontinu qui s'explique par la seule intervention d'une phase gazeuse.With regard to the part having received saw cuts, it can be seen that this part is boronised (FIGS. 10 and 11), not only on the two external faces (90 to 120 μm), but also on the internal faces defined by the saw cuts. A micrograph of these internal faces shows a borated layer of variable thickness and of discontinuous acicular character which is explained by the only intervention of a gas phase.

On tire de ces essais, la conclusion que la boruration en phase gazeuse étant parfaitement satisfaisante, il devient possible industriellement dans le r6acteur de séparer l'enceinte du générateur des agents gazeux borés (BF3 + Si02, B4C), des pièces métalliques à borurer qui peuvent être commodément disposées dans un lit de SiC ou bien le cas échéant, laissées nues.We draw from these tests, the conclusion that boruration in the gas phase being perfectly satisfactory, it becomes possible industrially in the reactor to separate the enclosure of the generator from borated gaseous agents (BF 3 + Si0 2 , B 4 C), parts metal to boron which can be conveniently arranged in a SiC bed or if necessary, left naked.

On voit que l'invention a permis de mettre au point un procédé original permettant de borurer tous les aciers jusqu'aux aciers à outil avec une fiabilité totale. Les procédés antérieurs conduisaient à des pièces de qualité médiocre sur les aciers doux (formation de deux couches FeB + Fe2B), la souplesse du procédé de l'invention alliée à l'utilisation d'un modérateur d'activation (Si02) permet, y compris dans les conditions industrielles, de réaliser des pièces de qualité suivie et satisfaisante. Des essais mécaniques ont montré que la tenue des couches obtenues sur acier d'outillage était de très benne facture. Comme avec les procédés connus, la boruration de l'acier inoxydable au chrome-nickel 18.10 reste de faible effet.It can be seen that the invention has made it possible to develop an original process making it possible to boron all steels up to tool steels with total reliability. The previous processes led to poor quality parts on mild steels (formation of two layers FeB + Fe 2 B), the flexibility of the process of the invention combined with the use of an activation moderator (Si0 2 ) allows, including in industrial conditions, to produce parts of consistent and satisfactory quality. Mechanical tests have shown that the behavior of the layers obtained on tool steel was of very good quality. As with the known methods, boronization of stainless steel to chromium-nickel 18.10 remains of weak effect.

En outre, d'un point de vue purement industriel, les avantages du procédé sont considérables : simplicité, souplesse, économie de main-d'oeuvre (non collage de la poudre aux pièces) et fiabilité totale d'après de nombreux essais effectués en vraie grandeur. Le prix de revient de l'opération est divisé par trois environ quant aux matières consommables et les manipulations sont réduites au minimum.In addition, from a purely industrial point of view, the advantages of the process are considerable: simplicity, flexibility, economy of labor (not sticking from powder to parts) and total reliability based on numerous full-scale tests. The cost of the operation is divided by approximately three as for consumable materials and handling is reduced to a minimum.

Les conditions opératoires précédentes sont les conditions préférées, mais il a été possible d'obtenir des résultats valables avec Al2O3 et MgO, étant noté toutefois que ces deux oxydes conduisent à une assez forte activité de l'effluent utilisé comme agent gazeux activateur, qui contient alors de l'anhydride borique B203. Le rôle modérateur de Si02 est finalement le plus favorable, ce qui le fait préférer.The preceding operating conditions are the preferred conditions, but it has been possible to obtain valid results with Al 2 O 3 and MgO, it being noted however that these two oxides lead to a fairly high activity of the effluent used as activating gas agent. , which then contains boric anhydride B 2 0 3 . The moderating role of Si0 2 is ultimately the most favorable, which makes it preferable.

Les durées, pourcentages et granulométries donnés dans la précédente description ne sont pas limitatifs. On pourra les faire varier en fonction de la vitesse désirée plus ou moins grande de formation et d'épaisseur de la couche. Certains de ces facteurs n'ont qu'une faible influence, comme, par exemple, la granulométrie de B4C et de SiC.The durations, percentages and particle sizes given in the previous description are not limiting. They can be varied as a function of the desired greater or lesser speed of formation and thickness of the layer. Some of these factors have only a slight influence, such as, for example, the particle size of B 4 C and of SiC.

Le demandeur a pu constater également de bons résultats avec d'autres carbures de bore que B4C, tels que les borures BnC, dans lesquels n est compris entre 4 et 10.The applicant has also been able to observe good results with boron carbides other than B 4 C, such as borides B n C, in which n is between 4 and 10.

On ne sortira pas du cadre de l'invention en alimentant en gaz activateur plusieurs enceintes de boruration 3 à partir d'une seule enceinte 2.It will not depart from the scope of the invention to supply activating gas to several boronization enclosures 3 from a single enclosure 2.

En ce qui concerne l'application de l'invention aux cermets, des essais ont été faits sur des outils au carbure de tungstène contenant des proportions variables de cobalt (ou nickel, ou fer) avec l'installation de la fig. 1. Avec un débit de BF3 de 1 à 5 1/h et en réglant la température de traitement entre 800 et 1100°C on obtient des pièces borurées.As regards the application of the invention to cermets, tests were carried out on tungsten carbide tools containing variable proportions of cobalt (or nickel, or iron) with the installation of FIG. 1. With a BF 3 flow rate of 1 to 5 1 / h and by setting the treatment temperature between 800 and 1100 ° C, borided parts are obtained.

A 950°C la phase principale détectée par diffraction des rayons X est CoB; le borure mixte W2CoB2 semble également présent, par contre W2B5 est absent. Selon la température, divers borures mixtes (W-Co) peuvent se former.At 950 ° C the main phase detected by X-ray diffraction is CoB; the mixed boride W 2 CoB 2 also seems to be present, on the other hand W 2 B 5 is absent. Depending on the temperature, various mixed borides (W-Co) can form.

Des essais d'usinage par chariotage de différents matériaux (carbone non graphité, inox Nickel --chrome 18-10, acier rapide, céramiques, ...) ont été effectués. On a observé que l'outil boruré montre une résistance à l'usure très supérieure à celle de l'outil non traité et que l'essai sur l'acier rapide montre que les outils borurés ou non se détériorent assez rapidement; toutefois, la coupe obtenue avec l'outil boruré est franche (les plaquettes non borurées ne permettent pas la coupe).Tests of machining by carriage of different materials (carbon not graphite, Nickel stainless steel - chromium 18-10, high speed steel, ceramics, ...) were carried out. It has been observed that the borated tool shows a wear resistance much higher than that of the untreated tool and that the test on high speed steel shows that the borated or non-borated tools deteriorate fairly quickly; however, the cut obtained with the borided tool is straightforward (the non-borided inserts do not allow the cut).

A la figure 12, on a représenté un mode de réalisation particulièrement simple d'un réacteur pour la mise en oeuvre du procédé de l'invention. La partie inférieure du réacteur constitue l'enceinte 3 fermée par un couvercle 40 étanche à joint 41 refroidi à l'eau. L'enceinte 2 est réalisée sous forme d'un récipient emboîtable dans le réacteur avant pose du couvercle 40. Le fond de l'enceinte 2 comprend la grille 4 pour retenir le sable et laisser passer le gaz d'activation et une grille 31 pour retenir le carbure de bore, de préférence pulvérulent. Une conduite 10 fixée à l'enceinte 2 traverse le couvercle pour amener BF3 à travers le sable de l'enceinte2.Le couvercle est traversé par une cheminée centrale 14 qui traverse également, de façon étanche, l'enceinte 2 pour aboutir près du fond du réacteur sous une grille 12 de retenue des pièces à borurer. La sonde thermométrique 9 peut être disposée dans la cheminée 14.In Figure 12, there is shown a particularly simple embodiment of a reactor for implementing the method of the invention. The lower part of the reactor constitutes the enclosure 3 closed by a watertight cover 40 with seal 41 cooled with water. The enclosure 2 is produced in the form of a container which can be fitted into the reactor before fitting the cover 40. The bottom of the enclosure 2 comprises the grid 4 for retaining the sand and letting the activation gas pass and a grid 31 for retain boron carbide, preferably powdery. A pipe 10 fixed to the enclosure 2 crosses the cover to bring BF 3 through the sand of the enclosure2. The cover is crossed by a central chimney 14 which also crosses, in a sealed manner, the enclosure 2 to end near the bottom of the reactor under a grid 12 for retaining the parts to be borided. The temperature probe 9 can be placed in the chimney 14.

Claims (18)

1) Procédé de traitement par boruration de pièces en matériau du groupe constitué par les alliages de métaux de la famille du fer (Fe, Ni, Co) et par les cermets, dans lequel on porte les pièces à une température opératoire de l'ordre de 850 à 1150°C en présence d'un agent borurant solide et on active la boruration en soumettant simultanément les pièces à l'action de contact du courant d'un agent fluoré gazeux dans des conditions opératoires de pression et de température définies, caractérisé en ce que l'agent fluoré gazeux contient du boroxole rifluoré (BOF)3.1) Method of treatment by boriding of parts of material from the group consisting of alloys of metals of the iron family (Fe, Ni, Co) and by cermets, in which the parts are brought to an operating temperature of the order from 850 to 1150 ° C in the presence of a solid boronizing agent and boriding is activated by simultaneously submitting the parts to the action of contact of the current of a gaseous fluorinated agent under defined operating conditions of pressure and temperature, characterized in that the gaseous fluorine-containing agent contains rifluorinated boroxole ( BOF ) 3 . 2) Procédé selon la revendication 1, dans lequel on utilise comme gaz de départ BF3 ou un mélange gazeux contenant BF3, caractérisé en ce qu'on produit l'agent fluoré gazeux contenant du boroxole trifluoré en faisant passer le gaz dé départ à travers une masse pulvérulente d'oxydes minéraux exempts d'impuretés cationiques, tels qu'oxyde simples ou complexes de silicium, d'aluminium et de magnésium, portée à une température au moins égale à 450°C.2) Process according to claim 1, in which BF 3 or a gaseous mixture containing BF 3 is used as the starting gas, characterized in that the gaseous fluorinated agent is produced containing trifluorinated boroxole by passing the starting gas to through a powdery mass of inorganic oxides free from cationic impurities, such simple oxide or silicon complex, aluminum and magnesium, heated to a temperature at least equal to 4 50 ° C. 3) Procédé selon la revendication 2, caractérisé en ce que la masse pulvérulente d'oxydes minéraux est constituée par un sable de silice.3) Method according to claim 2, characterized in that the pulverulent mass of mineral oxides consists of silica sand. 4) Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que l'agent fluoré gazeux d'activation est amené au contact des pièces à débit réglable.4) Method according to any one of claims 1 to 3, characterized in that the gaseous fluorinating agent of activation is brought into contact with the parts with adjustable flow. 5) Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que l'agent fluoré gazeux d'activation est amené au contact des pièces à une pression voisine de la pression atmosphérique.5) Method according to any one of claims 1 to 4, characterized in that the gaseous fluorinating activating agent is brought into contact with the parts at a pressure close to atmospheric pressure. 6) Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que l'agent fluoré gazeux d'activation et/ou le gaz de départ sont dilués dans un gaz vecteur neutre.6) Method according to any one of claims 1 to 5, characterized in that the fluorinated agent activation gases and / or the starting gas are diluted in a neutral carrier gas. 7) Procédé selon la revendication 2, caractérisé en ce que la masse pulvérulente d'oxydes minéraux est à une granulométrie sensiblement homogène comprise entre 0,1 et 2 mm environ.7) Method according to claim 2 , characterized in that the pulverulent mass of mineral oxides is at a substantially homogeneous particle size between 0.1 and 2 mm approximately. 8) Procédé selon la revendication 1, caractérisé en ce que l'agent borurant solide est un carbure de bore BnC, dans lequel n est compris entre 4 et 10.8) Method according to claim 1, characterized in that the solid boronating agent is a boron carbide B n C, in which n is between 4 and 10. 9) Procédé selon la revendication 1, caractérisé en ce que le bore de l'agent borurant solide et/ou de l'agent fluoré gazeux d'activation ou gaz de départ est enrichi ou appauvri en B10.9) Method according to claim 1, characterized in that the boron of the solid boronizing agent and / or of the gaseous fluorinating agent of activation or starting gas is enriched or depleted in B 10 . 10) Procédé selon la revendication 1, caractérisé en ce que l'agent borurant solide et les pièces à borurer sont soumis à l'action de contact du courant d'agent fluoré gazeux hors de contact mutuel.10) Method according to claim 1, characterized in that the solid boronizing agent and the parts to be boronized are subjected to the contact action of the stream of gaseous fluorinated agent out of mutual contact. 11) Procédé selon la revendication 1, caractérisé en ce que l'agent borurant solide présent avec les pièces à borurer est interposé dans le courant de l'agent fluoré gazeux en amont des pièces à borurer.11) Method according to claim 1, characterized in that the solid boriding agent present with the parts to be borided is interposed in the current of the gaseous fluorinated agent upstream of the parts to be borided. 12) Procédé selon la revendication 1, caractérisé en ce que les pièces à borurer sont disposées dans un lit constitué par une masse inerte granuleuse ou pulvérulente, telle que le carbure de silicium, pour y maintenir les pièces à borurer, comme il est connu en soi.12) Method according to claim 1, characterized in that the parts to be borided are arranged in a bed constituted by a granular or pulverulent inert mass, such as silicon carbide, to maintain the parts to be borided there, as is known in oneself. 13) Procédé selon la revendication 1, caractérisé en ce que l'agent borurant solide est disposé sous forme de matière solide pulvérulente constituant lit de traitement pour les pièces à borurer, comme il est connu en soi.13) Method according to claim 1, characterized in that the solid boriding agent is arranged in the form of pulverulent solid material constituting treatment bed for the parts to be borided, as it is known per se. 14) Procédé selon l'une quelconque des revendications 1 à 13, caractérisé en ce qu'on recycle, au moins partiellement, l'agent fluoré gazeux d'activation.14) Method according to any one of claims 1 to 13, characterized in that at least partially the fluorinated gaseous activating agent is recycled. 15) Dispositif pour la mise en oeuvre du procédé selon l'une quelconque des revendications 2 à 14 comportant une première enceinte de traitement de boruration et des moyens de chauffage de cette enceinte à une température de l'ordre de 850 à 1150°C, caractérisé en ce qu'il comporte : - une seconde enceinte pour une masse pulvérulente ou granuleuse d'oxydes minéraux, - des moyens de chauffage de ladite seconde enceinte à au moins 450°C environ, - des moyens d'amenée d'un gaz fluoré dans ladite seconde enceinte, - un passage de transfert de l'effluent gazeux fluoré de la seconde enceinte à la première enceinte, - des moyens d'évacuation de l'effluent gazeux fluoré de ladite première enceinte. 15) Device for implementing the method according to any one of claims 2 to 14 comprising a first enclosure for boriding treatment and means for heating this enclosure to a temperature of the order of 850 to 1150 ° C, characterized in that it comprises: - a second enclosure for a powdery or granular mass of mineral oxides, means for heating said second enclosure to at least approximately 450 ° C., means for supplying a fluorinated gas into said second enclosure, a passage for the transfer of the fluorinated gaseous effluent from the second enclosure to the first enclosure, - means for discharging the fluorinated gaseous effluent from said first enclosure. 16) Dispositif selon la revendication 15, caractérisé en ce qu'il comporte, dans la zone limitrophe aux deux dites enceintes, un moyen de retenue, perméable aux gaz, pour un lit interposé d'agent borurant solide fritté ou pulvérulent.16) Device according to claim 15, characterized in that it comprises, in the zone bordering on the two said enclosures, a retaining means, permeable to gases, for an interposed bed of sintered or pulverulent solid boriding agent. 17) Dispositif selon l'une quelconque des revendications 15 et 16, caractérisé en ce que le moyen d'évacuation de l'effluent gazeux de ladite première enceinte est une cheminée traversant les deux dites enceintes superposées.17) Device according to any one of claims 15 and 16, characterized in that the means for discharging the gaseous effluent from said first enclosure is a chimney passing through the two said superimposed enclosures. 18) Pièces d'aciers au carbone ayant subi en surface un traitement de boruration sur une épaisseur d'environ 20 à 200 µm caractérisées en ce qu'elles sont recouvertes d'une couche monophasée de cristaux de Fe2B de formation aciculaire.18) Parts of carbon steels having undergone a boriding treatment on the surface over a thickness of approximately 20 to 200 μm, characterized in that they are covered with a single-phase layer of Fe 2 B crystals of acicular formation.
EP80400252A 1979-02-27 1980-02-22 Process for boronizing articles made of metal or cermet, and articles provided with a boronized surface Ceased EP0015813A1 (en)

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US4289545A (en) 1981-09-15
ES8200929A1 (en) 1981-11-16
FR2450286A1 (en) 1980-09-26

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