Classifications

• • 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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
  • C23C10/34—Embedding in a powder mixture, i.e. pack cementation
  • C23C10/36—Embedding in a powder mixture, i.e. pack cementation only one element being diffused
  • C23C10/48—Aluminising
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • 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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
  • C23C10/34—Embedding in a powder mixture, i.e. pack cementation
  • C23C10/52—Embedding in a powder mixture, i.e. pack cementation more than one element being diffused in one step
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
  • C23C10/34—Embedding in a powder mixture, i.e. pack cementation
  • C23C10/52—Embedding in a powder mixture, i.e. pack cementation more than one element being diffused in one step
  • C23C10/54—Diffusion of at least chromium
  • C23C10/56—Diffusion of at least chromium and at least aluminium
• • 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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/60—After-treatment

Definitions

• the present invention relates to the production of a protective coating against corrosion on a substrate having cavities.
• Thermal spraying techniques such as plasma or flame projection involves sending molten or partially melted particles, at high speed, to the surface of the part to be protected.
• the coating is constructed in successive layers. These techniques can only be used on open or easily accessible surfaces.
• the vapor phase deposition techniques use a gaseous precursor of the coating to be produced.
• This precursor may be produced in the direct vicinity of the surface to be coated (carburized pack) or transported via a gas to the surface to be coated (out of pack, CVD from a bottle or gaseous mixture, etc.).
• the main difficulties encountered for the carburizing pack are related to the filling of parts having a complex geometry or very small dimensions (a few mm) with the cementum powder (precursor mixture of the coating).
• the main limitations of the techniques using gaseous precursors concern the rapid depletion of the gaseous mixture in reactive species resulting in heterogeneities of chemical composition and / or thickness of the coating. It is very difficult to obtain a homogeneous coating on large surfaces or in complex geometries.
• Physical vapor deposition techniques involve evaporating the component (s) of the coating prior to condensing them on the surface of the part to be coated. Evaporation is usually done by bombarding a target with a high energy beam (electrons or ions). The distance between the target and the surface to be coated is a major parameter for the homogeneity of the thickness of the deposit. These techniques are very difficult to use on parts of complex geometry or on non-accessible surfaces.
• the carburizing pack is a very old process for making a coating on a part.
• the latter is placed in a bed of cementum powder, which is a mixture of products capable of generating a reactive atmosphere at high temperature.
• This cementum should be placed close to the surface to be coated to produce a homogeneous coating in thickness and chemical composition.
• Coatings are conventionally made on parts having cavities of a few centimeters by filling the part with the cementum powder.
• a problem is to improve the deposition processes by pack cementation to allow their use for the substrate coating having cavities.
• a solution of the present invention consists in the use of a cementum in a pack-cementation deposition process on a substrate having cavities of minimum equivalent diameter e cm , characterized in that the cementum consists of spherical particles presenting each a diameter d such that d ⁇ e cm / 10.
• the size of the cement particles can be measured by laser granulometry or sieves to ensure that no particle or agglomerate of cement particles exceeds the maximum size required.
• a disagglomeration step may be necessary to "break" the agglomerates of elementary particles that may exceed the maximum size required.
• the equivalent diameters of the particles are conventionally comprised between ⁇ at 1 mm, preferably between ⁇ at ⁇ .
• the equivalent diameter is defined as the diameter of the cylinder or circle that fits into the smallest section giving access to the surface to be coated. Indeed, the latter does not necessarily have a standard form. Depending on the case, the use according to the invention may have one or more of the following characteristics:
• the cementum consists of spherical particles each having a diameter d such that d ⁇ e cm / 10.
• the cementum comprises a precursor of the element to be deposited, an activating agent and an inert diluent
• the cementum comprises 10 to 60% of metal powder as precursor of the element to be deposited, 5 to 40% of activating agent, and a complement of 100% of inert diluent, the inert diluent preferably comprising refractory oxides,
• the metal powder is made of aluminum or a mixture of aluminum with particles of Ni x Al y or of
• the cementum comprises a precursor of the element to be deposited, a stripping flux, and an inert diluent.
• the cement comprises an organic or inorganic binder.
• the organic binder may be PVA polyvinyl acetate and the inorganic binder may be SiO 2.
• the organic or inorganic binder be used during a step of atomizing the powder mixture. This optional step improves the flowability of the powder and thus the filling of the piece. It is to form spherical agglomerates of the powder mixture. This step will preferably be carried out under an inert atmosphere in order to prevent the surface oxidation of the metal powders which may be harmful for the deposition.
• the inert compound does not chemically intervene in the formation of the coating. Its main function is to avoid the densification of the cementum which would prevent its elimination after deposit. It is usually a very stable refractory compound. Its content is the complement of the other two.
• the solution according to the invention allows the realization of a deposit by pack cementation on parts of complex geometry and in inaccessible cavities.
• the cementum used in the context of the invention has a very good flowability to fill the smallest gaps (diameter ⁇ 1mm) and distribute evenly within the entire cavity to be coated.
• the particle size distribution and the morphology of the cement particles are the main parameters to ensure a good flowability of the mixture.
• the particle size distribution is adjusted according to the equivalent diameter of the smallest passage of the cavity.
• morphology spherical shapes which can be obtained by different grinding techniques for powders or powder mixture.
• An atomization treatment of the powder mixture may also be used to form spheres of the powder mixture.
• organic additives may be used to ensure a good cohesion of the spheres and a homogeneous dispersion of the elements of the mixture.
• the present invention also relates to two methods of depositing a coating by pack cementation on a substrate having cavities of minimum equivalent diameter e cm .
• the first method of depositing a coating by pack cementation on a substrate having cavities of minimum equivalent diameter e cm comprises the following successive steps:
• step b) introducing into the cavities of the substrate the cementum prepared in step a) by a vibratory system;
• the substrate-cement element is heated to a temperature below the melting temperature of the metal powder for a period of at least 6 hours at about 650 ° C for aluminum.
• the substrate-cement element is heated to a temperature of between 900 ° C. and 1150 ° C., preferably greater than 980 ° C.
• step c) the substrate-cement element is heated at about 650 ° C. for at least 6 hours.
• the first method may have one or more of the following characteristics:
• the particles of the cementum prepared in step a) are pre-activated by mechano-synthesis; preactivation makes it possible to increase the chemical reactivity of the precursor particles.
• This treatment facilitates the reaction between the precursor and the activator and therefore the deposition.
• the coating recovered in step g) comprises NiAl
• the coating recovered in step g) has a thickness of between 15 and
• the second method of depositing a coating by pack cementation on a substrate having cavities of minimum equivalent diameter e cm comprises the following successive steps:
• a cementitious consisting of a stripping flux and spherical particles of an inert diluent and a metal powder is prepared, said spherical particles each having a diameter d such that d ⁇ e cm / 10;
• step b) introducing into the cavities of the substrate the cementum prepared in step a) by a vibratory system;
• the substrate-cementation unit is heated to a temperature above the melting temperature of the pickling stream, under a primary vacuum or under an inert atmosphere (Ar), for a period of between 10 min and 2 h;
• the cement is subjected to a washing step so as to remove the cement residue
• the second method may have one or more of the following characteristics:
• the washing step e) is carried out by means of an acidified aqueous solution.
• the coating recovered in step f) comprises NiAl 3 .
• said process comprises, before step e), a step of heating the substrate-cementation unit at a temperature of between 900 ° C. and 1150 ° C., preferably greater than 980 ° C.
• the coating recovered in step f) comprises NiAl.
• the coating recovered in step f) has a thickness between 5 ⁇ and 200 ⁇ , preferably between 5 ⁇ and 80 ⁇ .
• FIG 1 shows schematically the different steps of the first method according to the invention.
• the first process consists in the use of a powder mixture consisting of the activating agent (5%), an inert diluent (Alumina, silica, etc.) and a metal to be deposited, a metal powder ( between 10 and 60%) which may be either pure aluminum or an Al + NIA1 or AlCr mixture and whose particles may or may not have been "pre-activated” by mechano-synthesis.
• the granulometry of the mixture is then adjusted so that it can be introduced into the channels by a vibratory system.
• the assembly is then brought to a temperature below the melting temperature of the metal to be deposited for a period of at least 6 hours.
• the assembly is again subjected to a vibration step for extracting the residual powder.
• the coating consists of a surface enrichment of aluminum substrate whose composition is close to NiAl 3 .
• the thicknesses obtained vary between 5 and 10 ⁇ depending on the time during which the first heating step was carried out.
• the part thus coated is brought to a temperature of between 900 ° C. and 1150 ° C., preferably greater than 980 ° C., so as to obtain the NiAl composition in a superficial edge of thickness ranging from 15 to 25 ⁇ m ( Figure 3).
• FIG. 2 schematizes the different steps of the second method according to the invention.
• the second method consists in the use of a powder mixture consisting of a low-melting pickling flux (K A1F 6 -KA1F 4 ) which is the element which has the lowest melting point of the mixture constituting the cement and particles of an inert diluent and a pure metal powder or aluminum alloy. (10 to 60% of metal powders, 40% of stripping flux and the balance of inert diluent).
• K A1F 6 -KA1F 4 low-melting pickling flux
• the whole is introduced by vibration as in the case of the first method and is heated to a high temperature, lower than the melting of the metal phase, but greater than that of the stripping flux for a time that varies from a few minutes to one or two hours. .
• the coating is obtained either under primary vacuum or inert controlled atmosphere (argon).
• the residues are then extracted by washing directly after the heat treatment step.
• the apparatus can be washed with a chemical solution (acidified aqueous).
• the coating thus obtained corresponds to a phase of composition close to NiAl which can be converted into NiAl in a subsequent annealing step at a temperature between 900 ° C and 1150 ° C, preferably at 980 ° C.
• the appearance of the coating is shown in FIG.
• the powder mixtures can be stored for long periods of time in a desiccator under a primary vacuum or in a dry chamber under a neutral gas sweep and are immediately ready for use.
• the inert diluent is selected from powders of refractory inert materials, more preferably from refractory mineral oxides, such as alumina, silica, magnesia and mixtures thereof, which are commonly used in cementation.
• refractory inert materials more preferably from refractory mineral oxides, such as alumina, silica, magnesia and mixtures thereof, which are commonly used in cementation.
• the substrate which can be provided with such a coating is generally chosen from metal substrates, for example iron or nickel base, alloy (s) substrates or superalloy (s), composite substrates comprising one or more metals and / or alloy (s) and / or superalloy (s) containing Ni to react with the deposited Al and form NiAl.
• metal substrates for example iron or nickel base, alloy (s) substrates or superalloy (s), composite substrates comprising one or more metals and / or alloy (s) and / or superalloy (s) containing Ni to react with the deposited Al and form NiAl.
• the substrate may be previously superficially enriched in Ni for example by electrolytic deposition.
• the treatments are generally carried out under a neutral or reducing atmosphere, for example under an atmosphere of hydrogen and / or argon, preferably under an argon atmosphere, or under an argon atmosphere with, for example, from 5 to 10% of argon. hydrogen.
• the pressure used during the treatment may be atmospheric pressure or a reduced pressure, for example a pressure of 10 " atm of argon.
• the coatings obtained by the processes according to the invention give the substrates an excellent resistance to corrosion, even within each substrate cavity regardless of its size.
• the photos of FIG. 3 show two samples of HR120 alloy, one (the one on the right) coated with the coating produced according to the second method according to the invention and the other (the left one) uncoated. These samples were subjected to a corrosive atmosphere consisting of (in% vol.): 15% CO, 5% CO 2 , 55% H 2 , 25% H 2 O, at a pressure of 21 bar absolute and a temperature of 650 ° C. After 4700 hours of exposure, it is clear that the coating deposited according to the second method of the invention can protect the alloy from corrosion.

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• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Engineering & Computer Science (AREA)
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• Crystallography & Structural Chemistry (AREA)
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• Physics & Mathematics (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Powder Metallurgy (AREA)
• Chemically Coating (AREA)
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• 2013
  • 2013-02-13 FR FR1351227A patent/FR3001976B1/fr not_active Expired - Fee Related
• 2014
  • 2014-02-04 US US14/767,795 patent/US20150368782A1/en not_active Abandoned
  • 2014-02-04 CN CN201480008464.5A patent/CN105164303B/zh not_active Expired - Fee Related
  • 2014-02-04 EP EP14708611.0A patent/EP2956566B1/de active Active
  • 2014-02-04 WO PCT/FR2014/050193 patent/WO2014125187A1/fr not_active Ceased
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• 2015
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