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
  • 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
• • 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
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/321—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer with at least one metal alloy 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
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/321—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer with at least one metal alloy layer
  • C23C28/3215—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer with at least one metal alloy layer 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
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/325—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer with layers graded in composition or in physical properties
• • 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
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide 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
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
  • C23C28/3455—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer with a refractory ceramic layer, e.g. refractory metal oxide, ZrO2, rare earth oxides or a thermal barrier system comprising at least one refractory oxide layer

Definitions

• the present invention relates to protective coatings for components exposed to high temperatures, such as components of a gas turbine engine. More particularly, this invention is directed to a process for forming a bond coat of a thermal barrier coating system, and specifically a dense multilayer bond coat having a desirable level of surface roughness to promote mechanical interlocking between the bond coat and a thermal barrier coating deposited on the bond coat.
• the operating environment within a gas turbine engine is both thermally and chemically hostile.
• Significant advances in high temperature alloys have been achieved through the formulation of iron, nickel and cobalt-base superalloys though components formed from such alloys often cannot withstand long service exposures if located in certain high-temperature sections of a gas turbine engine, such as the turbine, combustor or augmentor. Examples of such components include buckets and nozzles in the turbine section of a gas turbine engine.
• a common solution is to protect the surfaces of such components with an environmental coating system, such as an aluminide coating, an overlay coating or a thermal barrier coating (TBC) system.
• TBC thermal barrier coating
• the latter includes a layer of thermal-insulating ceramic (thermal barrier coating, or TBC) adhered to the superalloy substrate with an environmentally-resistant bond coat.
• Metal oxides such as zirconia (Zr ⁇ 2) that is partially or fully stabilized by yttria (Y2O3), magnesia (MgO) or another oxide, have been widely employed as the material for the thermal-insulating ceramic layer.
• the ceramic layer is typically deposited by air plasma spray (APS), vacuum plasma spray (VPS) (also called low pressure - 2 - plasma spray (LPPS)), or a physical vapor deposition (PVD) technique, such as electron beam physical vapor deposition (EBPVD) which yields a strain-tolerant columnar grain structure.
• APS is often preferred over other deposition processes because of low equipment cost and ease of application and masking.
• the adhesion mechanism for plasma-sprayed ceramic layers is by mechanical interlocking with a bond coat having a relatively rough surface, preferably about 350 microinches to about 750 microinches (about 9 to about 19 m) Ra.
• Bond coats are typically formed from an oxidation- resistant alloy such as MCrAlY where M is iron, cobalt and/or nickel, or from a diffusion aluminide or platinum aluminide that forms an oxidation-resistant intermetallic, or a combination of both. Bond coats formed from such compositions protect the underlying superalloy substrate by forming an oxidation barrier for the underlying superalloy substrate.
• the aluminum content of these bond coat materials provides for the slow growth of a dense adherent aluminum oxide layer (alumina scale) at elevated temperatures. This oxide scale protects the bond coat from oxidation and enhances bonding between the ceramic layer and bond coat.
• bond coats are typically applied by thermal spraying, e.g., APS, VPS and high velocity oxy-fuel (HVOF) techniques, all of which entail deposition of the bond coat from a metal powder.
• thermal spraying e.g., APS, VPS and high velocity oxy-fuel (HVOF) techniques, all of which entail deposition of the bond coat from a metal powder.
• HVOF high velocity oxy-fuel
• VPS processes typically employ powders having a very fine particle size distribution, with the result that as-sprayed VPS bond coats are dense but have relatively smooth surfaces (typically 200 to 350 microinches (about 4 to - 3 - about 9 m)) Ra. Consequently, plasma-sprayed ceramic layers do not adhere well to VPS bond coats.
• air plasma possesses a higher heat capacity in the presence of air.
• the higher heat capacity of the APS process enables the melting of relatively large particles, permitting the use of metal powders that yield bond coats having a rougher surface than is possible with VPS.
• the adhesion of a ceramic layer to an APS bond coat is enhanced by the rough APS bond coat surface, e.g., in the 350 to 750 microinch (about 9 to about 19 m) Ra range suitable for plasma-sprayed ceramic layers.
• the particle size distribution of such powders is Gaussian as a result of the sieving process, and is typically broad in order to provide finer particles that fill the interstices between larger particles to reduce porosity.
• Bond coats deposited by HVOF techniques are very sensitive to particle size distribution of the powder because of the relatively low spray temperature of the HVOF process. Accordingly, HVOF process parameters are adjusted to spray powders having a very narrow range of particle size distribution.
• a coarse powder must be used in an HVOF process.
• the resulting bond coat typically exhibits relatively high porosity and poor bonding between sprayed particles.
• a finer powder must typically be used, with the result that a thermal barrier coating does not adhere well - 4 - to the bond coat due to the bond coat lacking surface features that provide micro-roughness.
• a bond coat of a thermal barrier coating (TBC) system for components designed for use in a hostile thermal environment, such as turbine buckets and nozzles, combustor components, and augmentor components of a gas turbine engine. Also provided is a method of depositing the bond coat, which produces an adequate surface roughness for adhering a plasma-sprayed ceramic layer while also producing a bond coat that is sufficiently dense to inhibit diffusion of oxygen and other oxidizing agents to the component substrate. Consequently, bond coats produced by the method of this invention are protective and yield thermal barrier coating systems that are highly resistant to spallation.
• TBC thermal barrier coating
• the method generally entails forming a bond coat by depositing a first bond coat layer on a suitable substrate using a HVOF technique employing a first metallic powder having a maximum particle size of 55 micrometers, a suitable range being about 20 to 55 m.
• the resulting bond coat layer has a surface roughness of about 200 to about 450 microinches (about 5 to about 11 m) Ra.
• the first bond coat layer Prior to exposure to a high-temperature oxidizing environment, the first bond coat layer is heat treated in a vacuum or inert atmosphere to densify the first bond coat layer and diffusion bond the particles.
• a second bond coat layer is then deposited on the first bond coat layer by air plasma spraying a second metallic powder of particles having a size of from about 35 to about 110 micrometers.
• the particles are deposited to cause the second bond coat layer to have a porosity of less than 5% of theoretical density and a macro-surface roughness of about 450 to about 750 microinches (about 11 to about 19 m) Ra.
• the first and second bond coat layers Prior to exposure to a high-temperature oxidizing environment, the first and second bond coat layers are heat treated in a vacuum or inert atmosphere to diffusion bond the second bond coat layer to the first bond coat layer. Thereafter, a thermal-insulating ceramic layer can be deposited that adheres to the bond coat through mechanical interlocking with the rough surface of the second bond coat layer.
• the surface roughness of the resulting bi-layer bond coat is attributable to particles of the second metallic powder being incompletely melted during deposition, yielding a macro-surface roughness of at least about 450 microinches Ra.
• the finer particles of the second metallic powder fill the interstices between the larger particles to a degree sufficient to achieve a density of at least about 95% of theoretical.
• the finer particles of the second metallic powder also contribute to the micro-surface roughness of the bond coat, which has been determined to greatly enhance the adhesion of the thermal barrier coating when combined with the macro-surface roughness provided by the coarser particles.
• the method of this invention produces a low-porosity bond coat having a surface roughness necessary for a plasma-sprayed ceramic layer of a thermal barrier coating system. Accordingly, bond coats produced by the present invention are able to adhere plasma-sprayed ceramic layers, such that the thermal barrier coating system exhibits a desirable level of spallation resistance while inhibiting oxidation of the underlying substrate. - 6 -
• Figure 1 schematically represents a thermal barrier coating system having a bi-layer bond coat deposited in accordance with this invention.
• the present invention is generally applicable to metal components that are protected from a thermally and chemically hostile environment by a thermal barrier coating (TBC) system.
• TBC thermal barrier coating
• Notable examples of such components include the high and low pressure turbine nozzles and blades, shrouds, combustor liners and augmentor hardware of gas turbine engines, and buckets of industrial turbine engines. While the advantages of this invention are particularly applicable to turbine engine components, the teachings of this invention are generally applicable to any component on which a thermal barrier may be used to thermally insulate the component from its environment.
• FIG. 1 A partial cross-section of a turbine engine component 10 having a thermal barrier coating system 14 in accordance with this invention is represented in Figure 1.
• the coating system 14 is shown as including a thermal-insulating ceramic layer 18 bonded to a substrate 12 with a bi-layer bond coat 16.
• the substrate 12 may be formed of an iron, nickel or cobalt-base superalloy, though it is foreseeable that other high temperature materials could be used.
• the ceramic layer 18 is deposited by plasma spraying techniques, such as air plasma spraying (APS) and vacuum plasma spraying (VPS), the latter of which is also known as low pressure plasma spraying (LPPS).
• APS air plasma spraying
• VPS vacuum plasma spraying
• a preferred material for the ceramic layer 18 is an yttria-stabilized zirconia (YSZ), though other ceramic materials could be used, including yttria, partially stabilized - 7 - zirconia, or zirconia stabilized by other oxides, such as magnesia (MgO), ceria (Ce ⁇ 2) or scandia (SC2O3).
• YSZ yttria-stabilized zirconia
• MgO magnesia
• Ce ⁇ 2 ceria
• SC2O3 scandia
• the bond coat 16 must be oxidation-resistant so as to protect the underlying substrate 12 from oxidation and to enable the plasma-sprayed ceramic layer 18 to more tenaciously adhere to the substrate 12. In addition, the bond coat 16 must be sufficiently dense to inhibit the diffusion of oxygen and other oxidizing agents to the substrate 12. Prior to or during deposition of the ceramic layer 18, an alumina (AI2O3) scale (not shown) may be formed on the surface of the bond coat 16 by exposure to elevated temperatures, providing a surface to which the ceramic layer 18 tenaciously adheres.
• the bond coat 16 preferably contains alumina- and/or chromia-formers, i.e., aluminum, chromium and their alloys and intermetallics.
• Preferred bond coat materials include MCrAI and MCrAlY, where M is iron, cobalt and/or nickel.
• the bond coat 16 must have a sufficiently rough surface, preferably at least 350 microinches (about 9 m) Ra in order to mechanically interlock the ceramic layer 18 to the bond coat 16.
• the present invention produces the bond coat 16 to have sufficient density and surface roughness by depositing a first bond coat layer 16a using a high velocity oxy-fuel (HVOF) process and a relatively fine powder having a relatively narrow particle size distribution, followed by a second bond coat layer 16b deposited by air plasma spraying (APS) and using a coarser powder having a relatively broader particle size distribution.
• HVOF high velocity oxy-fuel
• APS air plasma spraying
• prior art HVOF bond coats are typically either too smooth to adequately adhere a plasma-sprayed bond coat, or have adequate surface roughness but at the expense of lower coating density and poor integrity, while prior art APS bond coats can be deposited to have adequate surface roughness but undesirably high porosity, e.g., less than 95% of theoretical density.
• the present invention provides a dense multilayer - 8 - bond coat 16 having desirable surface roughness, e.g., at least 350 microinches Ra.
• the HVOF and APS processes of this invention require the use of two metal powders with different particle size distributions.
• At least the second bond coat layer 16b, and preferably both bond coat layers 16a and 16b are formed of an oxide scale-forming metal composition, such as an aluminum-containing intermetallic, chromium-containing intermetallic, MCrAI, MCrAlY, or a combination thereof.
• a particularly suitable composition for both bond coat layers 16a and 16b has a nominal composition, in weight percent, of about 22% chromium, about 10% aluminum, about 1 % yttrium, the balance nickel and incidental impurities.
• the HVOF bond coat layer 16a provides a very dense barrier to oxidation as a result of the fine powder having a narrow particle size distribution range, while the second layer 16b has a desirable micro-surface roughness and macro- surface roughness attributable to the finer and coarser particles, respectively, present in the powder used with the APS process.
• the resulting combination of micro- and macro-roughness has been found to promote the mechanical interlocking capability of the bond coat 16 with the subsequently-applied ceramic layer 18.
• the powder for the HVOF process has a maximum particle size of about 55 m.
• a preferred particle size distribution is, in weight percent, about 19% particles from 44 to 55 m, about 42% particles from 31 to 44 m, about 31 % particles from 22 to 31 m, and about 5% particles from 16 to 22 m.
• Preferred parameters include a spray rate of about three to eight pounds (about 1.4 to 3.6 kg) per hour, a spray distance of about five to twelve inches (about 0.13 to 0.30 meter), a fuel gas mixture of oxygen, hydrogen and nitrogen, and a maximum surface temperature of about 350 F (about 175 C).
• the powder for the APS process preferably has a particle size range of about 35 to 110 m.
• a preferred particle size distribution is, in weight percent, about 5% particles from 75 to 90 m, about 25% - 9 - particles from 63 to 75 m, about 50% particles from 53 to 63 m, about 15% particles from 45 to 53 m, and about 5% particles from 38 to 45 m.
• Preferred parameters include a spray rate of about twenty to sixty grams per minute, a spray distance of about three to six inches (about 0.08 to 0J5 meter), and a current level of about 350 to 650 amps using a gas mixture of hydrogen and nitrogen.
• a suitable thickness for the HVOF bond coat layer 16a is about 100 to about 300 micrometers.
• the HVOF process and powder described above produce a bond coat layer 16a having a surface roughness of about 200 to about 450 microinches (about 5 to about 11 m) Ra and a density of at least about 99% of theoretical.
• the bond coat layer 16a Prior to exposure to a high-temperature oxidizing environment, the bond coat layer 16a is heat treated to diffusion bond the powder particles and densify the bond coat layer 16a.
• the heat treatment also preferably diffusion bonds the layer 16a to the substrate 12.
• a preferred treatment is a temperature of about 950 C to about 1150 C and a duration of about one to about six hours in a vacuum or inert atmosphere.
• the bond coat layer 16a is also preferably degreased to remove all dirt, grease and other potential contaminants.
• the APS bond coat layer 16b is then deposited on the
• the HVOF bond coat layer 16a using the above-described process and powder.
• the preferred APS powder described above contains a sufficient amount of coarser particles to produce an adequate surface macro-roughness for the bond coat 16, and a sufficient amount of finer particles to yield an adequate surface micro-roughness for adhesion of the ceramic layer 18 and also fill the interstices between the coarser particles to increase the density of the APS bond coat layer 16b.
• the resulting bond coat 16 has a surface roughness of about 350 microinches to about 750 microinches (about 9 to about 19 m) Ra.
• the bond coat layer 16b Prior to exposure to a high-temperature oxidizing environment, the bond coat layer 16b is also subjected to a heat treatment sufficient to diffusion bond the APS bond coat layer 16b to the HVOF bond coat layer 16a.
• a preferred treatment is a temperature of about 950 C to about 1150 C and a duration of about - 10 - one to about six hours in a vacuum or inert atmosphere, and yields a coating density of at least about 95% of theoretical (i.e., porosity of not more than 5%).
• a suitable thickness for the APS bond coat layer 16b is about 100 to about 300 micrometers.
• the substrate material for all specimens was a nickel-base superalloy having a nominal composition, in weight percent, of 14 Cr, 9.5 Co, 3 Al, 4.9 Ti, 1.5 Mo, 3.8 W, 2.8 Ta, 0.010 C, balance Ni and incidental impurities.
• the bond coat composition for all specimens was the NiCrAIY material described above, having a nominal composition, in weight percent, of about 22% chromium, about 10% aluminum, about 1 % yttrium, the balance nickel and incidental impurities.
• the HVOF and APS bond coat layers of this invention were deposited from powders having the preferred particle size distributions stated above, while the powder deposited by VPS had a particle size range of about 10 to about 90 m.
• the HVOF process parameters included a hydrogen gas flow of about 1600 standard cubic feet per hour (scfh), an oxygen gas flow of about 450 scfh, a nitrogen gas flow of about 800 scfh, and a carrier (nitrogen) gas flow of about 30 scfh.
• the APS process parameters included a nitrogen gas flow of about 125 scfh, a hydrogen gas flow of about 9 scfh, and a carrier (nitrogen) gas flow of about 20 scfh (two injectors, 10 scfh per injector).
• the HVOF and APS bond coat layers had thicknesses of about 200 and about 100 m, respectively, while the VPS bond coats had thicknesses of about 300 m. All specimens were heat treated at about 1080 C for a duration of about four hours in a vacuum after each deposition step.
• the bond coats of this invention were characterized by a surface roughness of about 450 to 600 microinches Ra and a density (APS layer) of about 98% of theoretical, while the VPS bond coats were characterized by a surface roughness of about 450 to 600 microinches Ra and a density of about 99% of theoretical.
• furnace testing was performed. Some of the specimens were subjected to thermal cycle testing that consisted of 45 minute cycles at about 2000 F (about 1095 C) over a 20-hour period, by which spallation resistance of the ceramic layer was evidenced by the number of thermal cycles survived before spallation. A second test entailed subjecting specimens to 2000 F for 1000 hours, by which depletion of aluminum in the substrate was determined by post-test examination. The results of the furnace tests are summarized below.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Inorganic Chemistry (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Ceramic Engineering (AREA)
• Coating By Spraying Or Casting (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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• 1999
  • 1999-02-26 WO PCT/US1999/004339 patent/WO1999043861A1/en active IP Right Grant
  • 1999-02-26 DE DE69925590T patent/DE69925590T2/de not_active Expired - Fee Related
  • 1999-02-26 EP EP99908549A patent/EP1076727B1/en not_active Expired - Lifetime
  • 1999-02-26 CZ CZ20004537A patent/CZ300909B6/cs not_active IP Right Cessation

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