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
  • C23C10/30—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes using a layer of powder or paste on the surface
• • 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
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat

Definitions

• the invention relates to a method for coating hollow bodies, in which a Powder mixture of a metal donor powder, an inert filler powder and a Activator powder is provided, the powder mixture with a to be coated inner surface of the body, e.g. from a Ni, Co or Fe base alloy, in Contact is brought and heated.
• a Powder mixture of a metal donor powder, an inert filler powder and a Activator powder is provided, the powder mixture with a to be coated inner surface of the body, e.g. from a Ni, Co or Fe base alloy, in Contact is brought and heated.
• the achievable inner layer thicknesses are also limited here, because the coating gas or the donor metal gas on its way through the cavities of the component is depleted and a Schichtdickengradient over the length of the cavity arises. Because the layer thickness of the outer coating is due to the process above that the inner coating is, the life of the components is due to the thinner Inner coating limited.
• DE 30 33 074 A1 discloses a method for diffusion coating the inner surface of cavities, in which a metallic workpiece with an aluminizing diffusion powder mixture of 15% aluminum powder having a particle size of 40 microns and 85% alumina powder having a particle size of about 200 to 300 microns and a NH 4 CL powder can be coated.
• US 5,208,071 discloses a method for aluminizing a ferritic component with an alumina slurry and subsequent heat treatment, wherein the slip of at least 10 wt .-% chromium, at least 10 wt .-% inert Filling material, at least 12 wt .-% water, a binder and a halogen activator and the coated ferritic component is finally heat treated becomes.
• the use of a slurry differs procedurally clearly from a powder pack coating process.
• the composition of the Coating powder may contain 10 to 60% chromium powder, 0.1 to 20% chromium halide and alumina.
• the problem underlying the present invention is a powder packing method to improve the genus described above so that the Layer thicknesses of the inner coating even with cavities with relative complicated geometries are sufficiently large.
• the inert filling powder with an average particle size approximately is equal to the average particle size of the metal donor powder provided will that the metal dispenser powder and the inert Grepulver be provided with an average particle size greater than 40 microns, and that a powder mixture with a proportion of the metal donor powder of 10 to 25 wt .-% is provided.
• Such Powder mixture is good free flowing and has access in narrow edges of too coating internal cavities. It can be hollow body, such as guide and blades of gas turbines made of heat-resistant Ni, Co or Fe base alloys.
• the layer thicknesses of the inner coating are also in narrow edges or gusset areas of the cavities in the range of 50 to 110 microns and ensure thus the function of the inner coating as an oxidation and corrosion protection layer.
• the metal dispenser powder and the inert Filler powders are provided with an average particle size of greater than 40 microns, whereby a good permeation of the coating gas through the bed the powder mixture can be done.
• the powder mixture is mixed with a portion of the metal donor powder of 10 to 25 wt .-% provided to prevent the clumping of the powder mixture and to ensure a good permeation through the bed.
• the metal donor powder is an alloy with a proportion of the donor metal of 20 to 80 wt .-% is provided so ensures a sufficiently thick layer due to the high donor metal content is.
• the metal dispenser powder is a mixture of an alloy with a donor metal content of 40 to 70 wt .-% and an alloy with a donor metal content of 30 to 50 wt .-% is provided so that the depletion of the metal dispenser in the two alloys stepwise, i. with temporal Delay, takes place.
• the metal donor powder and the inert filler powder can with an average or average particle size of 150 microns are provided.
• Such Powder mixture is easily pourable and fills the cavities with the to be coated Inside surfaces due to a favorable specific bulk density good. In addition, there is a good permeation of the coating gas through the bed the powder mixture.
• the hollow body of a hollow turbine vane is a Gas turbine, which is provided with an oxidation and corrosion protection layer.
• the cavity has a length of about 160 mm. Its inner surfaces are spaced between 2 and 6 mm and converge at two opposite end portions.
• a powder mixture of about 20% by weight of metal donor powder and about 80% by weight of inert filler powder is provided.
• AlCr is chosen as the metal donor powder and Al 2 O 3 as the inert filling powder.
• the melting point of AlCr is at least about 100 ° C above the coating temperature of about 800 ° C-1200 ° C, so that diffusion bonding of the metal particles to each other or clogging does not occur.
• the proportion of an activator powder is about 3 wt .-%, with AlF 3 , that is, a halide compound is selected.
• a halide compound is selected.
• CrCl 3 is also considered as a compound for the activator powder.
• Such a compound must have a low vapor pressure at the coating temperature to be maintained throughout the coating process.
• a halide compound of the donor metal here aluminum, is used to avoid agglomeration due to a chemical reaction of the halogen with the donor metal.
• the proportion of aluminum, i. of the metal dispenser, on the metal dispenser powder is 50% by weight.
• the thus prepared powder mixture is in the cavity of the vanes for Filled coating of the inner surfaces.
• the subsequent coating takes place at 1080 ° C and a hold time of 6 hours, with the outer coating, i. the coating of the outer surfaces of the vane, simultaneously in one Einicinprozeß with a conventional powder packing method or by a Gas diffusion coating process can be done.
• the Al content in the layer is in the thus deposited inner coating between 30 and 35% by weight.
• an inert filling powder (Al 2 O 3 ) having an average particle size of about 100 ⁇ m is selected, which constitutes about 80% by weight of the powder mixture.
• activator powder AlF 3 is selected and mixed with about 3 wt .-% of a powder mixture.
• the metal donor powder which has a share of about 20% by weight of the powder mixture, of two fractions.
• the first Fraction is an alloy of AlCr in which the proportion of aluminum is 50% by weight. is.
• the second fraction the proportion of the donor metal, aluminum, is lower and is 30 wt .-%.
• the Al content in the inner layers is 24 to 28 wt .-%.
• the inner layer thicknesses lie between 65 and 105 microns and thus clearly over those with conventional (Powder Pack) method achievable layer thicknesses.
• the hollow body is a hollow turbine nozzle of a gas turbine, which is provided with an oxidation and corrosion protection layer by a powder-pack coating method.
• the elongated cavity is about 180 mm long.
• the inner surfaces are spaced between 2 and 6 mm and converge at two opposite longitudinal side end portions.
• a powder mixture of about 15 wt .-% metal donor powder and just below 85 wt .-% inert filler powder is provided to coat the inner surface of the vane.
• the proportion of metal donor powder can be in the range from 10 to 25% by weight.
• the metal donor powder is AlCr and the inert filler powder is Al 2 O 3 .
• the activator powder used is a halogen compound such as AlF 3 , the proportion of which is about 3% by weight.
• the activator powder is thus a halide compound of the donor metal Al.
• the mean particle size of the inert filler powder is about the same as the mean particle size of the metal donor powder and is 150 microns.
• the share of Donor metal Al on the metal donor powder which is an alloy is 50% by weight.
• the specific gravity of such a powder pack mixture is not due to a high proportion of the metal donor powder, but due to the selected Particle size distribution high. In this bed of powder mixture there is sufficient permeation of the halide compound originating coating gases.
• the coating of the inner surface of the turbine vane is the so provided powder mixture filled in the cavity.
• the subsequent coating takes place at 1080 ° C and a holding time of 6 H. It can be used simultaneously with the outer coating, i. the coating of the outer Surface of the turbine vane, which according to a conventional powder packing method or by a gas diffusion coating process can be done. In general, the coating will be at multiple turbine vanes performed simultaneously.
• the Al content in the inner coating deposited in this way is intermediate 30 and 35 wt .-% and thus in a very advantageous range, i. it occurs z. B. no embrittlement of the layer.
• the layer thicknesses are also in narrow edges or gusset area of the cavities in the range of 60 to 110 microns, so that the function of the inner coating as oxidation and corrosion protection is guaranteed.

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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)
• Other Surface Treatments For Metallic Materials (AREA)
• Powder Metallurgy (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)

Applications Claiming Priority (3)

Publications (3)

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• 1998
  • 1998-12-10 DE DE19856901A patent/DE19856901C2/de not_active Expired - Fee Related
• 1999
  • 1999-12-09 WO PCT/DE1999/003942 patent/WO2000034547A2/de active IP Right Grant
  • 1999-12-09 DE DE59904502T patent/DE59904502D1/de not_active Expired - Lifetime
  • 1999-12-09 EP EP99967878A patent/EP1144708B1/de not_active Expired - Lifetime
  • 1999-12-09 ES ES99967878T patent/ES2192415T3/es not_active Expired - Lifetime
  • 1999-12-09 US US09/857,763 patent/US6887519B1/en not_active Expired - Lifetime

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