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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
  • C23C28/021—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer
  • C23C28/022—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer with at least one MCrAlX layer
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
  • C23C28/028—Including graded layers in composition or in physical properties, e.g. density, porosity, grain size
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas

Definitions

• the invention relates to a method of depositing the bond coating according to the preamble of claim 1.
• MCrAIY protective overlay coatings are widely known in the prior art. They are a family of high temperature coatings, wherein M is selected from one or a combination of iron, nickel and cobalt.
• US-A-3,528,861 or US-A-4,585,481 are disclosing such kind of oxidation resistant coatings.
• US-A-4,152,223 discloses such method of coating and the coating itself.
• MCrAIY coatings which are based on a ⁇ / ⁇ '-gamma/gamma prime-structure.
• the advantages of ⁇ / ⁇ '-coatings is that they have a negligible thermal expansion mismatch with alloy of the underlying turbine article.
• the ⁇ / ⁇ '-coating are more convenient compared to the ⁇ / ⁇ -type of MCrAIY-coatings.
• a higher thermal fatigue resistance in coatings is most desirable since failure of the most turbine blades and vanes at elevated temperature is typically thermal fatigue driven.
• the ⁇ / ⁇ '-type of MCrAIY coatings known e.g. from US-A-4,973,445, are relatively new.
• the unique feature of this type of ⁇ / ⁇ '-coatings is that their thermal expansion mismatch is close to zero in combination with a high ductility, what make these coatings more resistant to thermal fatigue.
• the limitations are the low aluminum content and hence their low reservoir of aluminum.
• Thermal-Barrier-Coatings are known from different patents.
• US-A-4,055,705, US-A-4,248,940, US-A-4,321,311 or US-A-4,676,994 disclose a TBC-coating for the use in the turbine blades and vanes.
• the ceramics used are yttria stabilized zirconia and applied by plasma spray (US-A-4,055,705, US-A-4,248,940) or by electron beam process (US-A-4,321,311, US-A-4,676,994) on top of the MCrAIY bond coat.
• US-A-5,894,053 developed a process for applying a particulate metallic adhesion layer for ceramic thermal barrier coatings to metallic components.
• the essential content of the patent is a process of forming a roughened surface by applying particulate materials on the surface using binder, principally soldering power.
• the disadvantages of the process are the depression of the melting point of coating by soldering, a potential fatigue debits of the bond coating and the fluxing of the Thermally Grown Oxide (TGO) by the soldering material.
• TGO Thermally Grown Oxide
• a method of depositing a bond MCrAIY-coating according to the preamble of claim 1 was found, wherein before the TBC is applied, an inner layer on top of the surface of the article consisting of ⁇ / ⁇ '-MCrAlY is deposited using powder in the size range from 5 to 65 ⁇ m and an outer bond coating layer on top of the inner layer, which outer layer is more coarse than the inner layer and consisting of ⁇ -NiAl or ⁇ / ⁇ -MCrAlY or ⁇ / ⁇ '-MCrAlY, is deposited using powder in the size range from 30 to 125 ⁇ m.
• the inner layer on top of the surface of the article is deposited using powder in the size range from 15 to 50 ⁇ m, most preferable below 30 ⁇ m, and the outer layer on top of the inner layer is deposited using powder with a particle size from 35 to 90 ⁇ m.
• the outer bond coating layer is deposited using a powder which is more coarse then the underlying inner layer, the surface roughness and the TBC adherence is significantly increased.
• the deposited bond coating can be heat-treated at temperatures up to 1140°C, which is possible in air, argon, vacuum or an environment conductive to form the alumina scale, which further increases the TBC adherence. Beside that the heat-treatment stabilizes the coating.
• the outer layer can as well be aluminized using a pack or an out of pack gas phase diffusion process.
• the coating can be applied by a galvanic or plasma spray or any other conventional Plasma Vapor Deposition (PVD) method used for deposition of overlay and bond coatings.
• PVD Plasma Vapor Deposition
• the bond MCrAIY-coating consists of two different layers.
• An inner layer on top of the surface of the article consisting of MCrAIY with a structure of ⁇ / ⁇ '.
• the inner layer is deposited with a powder in the size range from 5 to 65 ⁇ m.
• An outer layer on top of the inner layer consists of ⁇ -NiAl, ⁇ / ⁇ -MCrAlY or even of ⁇ / ⁇ '-MCrAlY. But, in contradiction to the inner layer, the outer layer is deposited with a coarse powder in the size range from 30 to 125 ⁇ m.
• a ceramic coating such as TBC is deposited on top of the outer bond coating layer. Due to the fact that the outer bond coating layer is deposited using a powder which is more coarse then the underlying inner layer, the surface roughness and the TBC adherence is significantly increased.
• the inner layer on top of the surface of the article is deposited using powder in the size range from 15 to 50 ⁇ m, most preferable below 30 ⁇ m, and the outer layer on top of the inner layer is deposited using powder with a particle size from 35 to 90 ⁇ m.
• the technology disclosed in this invention directly translates lifetime improvement by increasing TBC adherence due to enhanced surface roughness of the external layer.
• the composition microstructure of the outer layer can also be independently adjusted to allow formation of an alumina scale beneath the TBC.
• An example is the use of ⁇ -NiAl or ⁇ / ⁇ -MCrAlY or even ⁇ / ⁇ '-MCrAlY as the outer layer.
• the inner layer of ⁇ / ⁇ '-MCrAlY comprises one or a combination of Y, Hf, Zr and Si with (wt-%) 0.01 - 5% Y+Hf+Zr+Si and one or a combination of Ta, Fe, Ga, Mg and Ca.
• the outer layer may consist of a ⁇ -NiAl outer layer and the ⁇ -NiAl may contain aluminum from about 20 to 33 wt.-%, which falls in the single phase range of NiAl phase diagram.
• the ⁇ -NiAl has a high oxidation resistance which can be further enhanced by a minor elemental addition. This is known e.g. from the patents US-A-4,610,736, US-A-5,116,438, US-A-5,516,380, US-A-5,116,691, US-A-4,961,905, US-A-4,478,791 or US-A-5,215,831.
• a possible content of the inner layer of ⁇ -NiAl is (wt-%) 0.001 - 0.5% Y, 0.001 - 0.5% Hf, 0.001 - 0.5% Zr, 0.1 - 1.5% Si, 0 - 1.0% Ca, 0 - 1.0% Mg, 0 - 4% Ga, 0 - 4% Fe, 0.1 - 4.0% Ta.
• the deposited bond coating may be heat-treated at temperatures of up to 1140°C, which can be done in air, argon, vacuum or an environment conductive to form the alumina scale, which further increases the TBC adherence. Beside that the heat-treatment stabilizes the microstructure of the coating. Thereby, the 1140°C heat-treatment has been found to be most advantageous to fully stabilize the microstructure.
• the 1140°C heat-treatment can also be used to pre-form alumina prior to TBC deposition.
• the outer layer can be aluminized using a pack or an out of pack gas phase diffusion process.
• the coating can be applied by a galvanic or plasma spray or any other conventional PVD method used for deposition of overlay and bond coatings.

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Cited By (14)

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Citations (4)

• 2001
  • 2001-05-25 EP EP01112646A patent/EP1260608A1/en not_active Withdrawn
• 2002
  • 2002-05-23 JP JP2002149052A patent/JP2003055753A/ja active Pending

Patent Citations (4)

Non-Patent Citations (2)

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