Patent Publication Number: US-10775115-B2

Title: Thermal spray coating method and thermal spray coated article

Description:
FIELD OF THE INVENTION 
     The present invention is directed to coating methods and coated articles. More particularly, the present invention is directed to thermal spray coating methods and thermal spray coated articles. 
     BACKGROUND OF THE INVENTION 
     Components, such as airfoils, cooling fins, and fingers, in various equipment are often subjected to increasingly high temperatures. These high temperatures can typically require a cooling mechanism to reduce component temperature and prevent damage to the component. 
     One known cooling mechanism includes cooling channels positioned near a hot surface, such as a hot gas path, of a component. In one mechanism, the cooling channels can have a cooling medium in them, such as a gas or a liquid. The cooling medium transports heat away from a region of the component to provide cooling. 
     In addition to the cooling channels, components are often thermally sprayed with an environmental coating to handle high temperatures. Applying the environmental coating can result in feedstock filling the cooling channels. Filling of the cooling channels can restrict or stop flow of the cooling medium, thereby reducing or eliminating the cooling provided by the cooling mechanism. 
     A coating method and coated article that do not suffer from one or more of the above drawbacks would be desirable in the art. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In an exemplary embodiment, a thermal spray coating method includes positioning a covering on a cooling channel of a component, and thermal spraying a feedstock onto the covering. The covering prohibits the feedstock from entering the cooling channel in the component and is not removed from the component. 
     In another exemplary embodiment, a thermal spray coating method includes providing a component comprising a substrate material, providing a cooling channel on a surface of the component, positioning a covering on the cooling channel, and thermal spraying a feedstock onto the component and the covering, the feedstock comprising a bond coat material. The covering prohibits the feedstock from entering the cooling channel. 
     In another exemplary embodiment, a thermal spray coated article includes a component, a cooling channel on a surface of the component, a covering on the cooling channel, and a thermally sprayed coating on the component. 
     Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a thermal spray coating method according to an embodiment of the disclosure. 
         FIG. 2  shows a mesh covering according to an embodiment of the disclosure. 
         FIG. 3  shows a perspective view of an article coated by a thermal spray coating method according to an embodiment of the disclosure. 
         FIG. 4  shows a cross-sectional view corresponding to the article of  FIG. 3 . 
     
    
    
     Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Provided are exemplary thermal spray coating methods and thermal spray coated articles. Embodiments of the present disclosure, in comparison to methods not utilizing one or more features disclosed herein, permit an increase in effectiveness of thermal cooling channels, permit an increase in flow of a cooling medium through the thermal cooling channels, permit an increase in efficiency of thermal spraying, permit a decrease in coating thickness over thermal cooling channels, decrease contamination of thermal cooling channels during thermal spraying, or a combination thereof. 
     Referring to  FIG. 1 , in one embodiment, a thermal spray coating method includes positioning a covering  102  on one or more cooling channels  105  in a component  101 , and thermal spraying a feedstock  104  onto the component  101  and the covering  102 . The covering  102  prohibits the feedstock  104  from entering the cooling channel  105  in the component  101 . In one embodiment, the feedstock  104  includes a bond coat material. 
     Suitable coverings  102  include, but are not limited to, a mesh, a foil, or a combination thereof. Suitable forms of the covering  102  include, but are not limited to, planar, curved, molded, contoured, complex, a strip, a sheet, or a combination thereof. For example, in one embodiment, the covering  102  is cut into strips and applied over the surface of the component  101 , the strips limited to covering the cooling channel  105  ( FIG. 1 ). In another example, the covering  102  is applied over the entire surface of the component  101  ( FIG. 4 ). 
     As used herein, the term “mesh” refers to an arrangement formed from a pattern of interwoven fibers  203  ( FIG. 2 ), machined interwoven foil, or a combination thereof. Suitable patterns of interwoven fibers  203  include, but are not limited to, plain weave, twill, plain dutch weave, twill dutch, twill dutch double, stranded, or a combination thereof. As used herein, the term “foil” refers to a deformable sheet made of any suitable material. Suitable foil configurations include, but are not limited to, those having openings  204 , being devoid of the openings  204 , or a combination thereof. The foil is resilient and is resistant to deformation from a thermal spraying nozzle  103 . The mesh is pliable, for example, capable of extending around a radius of about 30 mils without structural damage. In one embodiment, the mesh or the foil is selected as the covering  102 , and the thermal spraying nozzle  103  is positioned corresponding to the selected material to reduce or eliminate deformation of the covering  102 . 
     In one embodiment, the covering  102  is formed by, for example, electrical discharge machining (EDM), metal injection molding, thin sheet processing, or a combination thereof. The covering  102  is either pre-formed or post-formed. Pre-formed includes forming the covering  102  prior to positioning the covering  102  on the component  101 . Post-formed includes forming the covering  102  in position on the component  101 . In one embodiment, the covering  102  is temporarily or permanently secured to the component  101 . Suitable techniques for the securing of the covering  102  to the component  101  include, but are not limited to, tack welding, plating, sintering, brazing, or a combination thereof. 
     Suitable compositions of the covering  102  include the substrate material, the bond coat material, or a combination thereof. In one embodiment, the substrate material includes, but is not limited to, cobalt, chromium, tungsten, carbon, nickel, iron, silicon, molybdenum, manganese, alloys thereof, nickel-based alloy, a cobalt-based alloy, superalloys, intermetallics (TiAl and/or NiAl), ceramic matrix composites, or a combination thereof. In one embodiment, the bond coat material includes, but is not limited to, Ba 1-x Sr x Al 2 Si 2 O 8  (BSAS), ceramic oxides, (Yb,Y) 2 Si 2 O 7 , mullite with BSAS, Silicon and/or Yttrium mono and/or disilicates, or a combination thereof. 
     A suitable nickel-based alloy for use as the substrate material includes, by weight, about 14% chromium, about 9.5% cobalt, about 3.8% tungsten, about 1.5% molybdenum, about 4.9% titanium, about 3.0% aluminum, about 0.1% carbon, about 0.01% boron, about 2.8% tantalum, and a balance of nickel and incidental impurities. 
     Another suitable nickel-based alloy includes, by weight, about 7.5% cobalt, about 9.75% chromium, about 4.20% aluminum, about 3.5% titanium, about 1.5% molybdenum, about 4.8% tantalum, about 6.0% tungsten, about 0.5% columbium (niobium), about 0.05% carbon, about 0.15% hafnium, about 0.004 percent boron, and the balance nickel and incidental impurities. 
     Another suitable nickel-based alloy for use as the substrate material includes, by weight, between about 0.07% and about 0.10% carbon, between about 8.0% and about 8.7% chromium, between about 9.0% and about 10.0% cobalt, between about 0.4% and about 0.6% molybdenum, between about 9.3% and about 9.7% tungsten, between about 2.5% and about 3.3% tantalum, between about 0.6% and about 0.9% titanium, between about 5.25% and about 5.75% aluminum, between about 0.01% and about 0.02% boron, between about 1.3% and about 1.7% hafnium, up to about 0.1% manganese, up to about 0.06% silicon, up to about 0.01% phosphorus, up to about 0.004% sulfur, between about 0.005% and about 0.02% zirconium, up to about 0.1% niobium, up to about 0.1% vanadium, up to about 0.1% copper, up to about 0.2% iron, up to about 0.003% magnesium, up to about 0.002% oxygen, up to about 0.002% nitrogen, balance nickel and incidental impurities. 
     Referring to  FIG. 2 , in one embodiment, the openings  204  in the covering  102  have a first dimension, such as a first width  201 , and a second dimension, such as a second width  202 . The first width  201  and the second width  202  at least partially define a predetermined area. The predetermined area of the openings  204  in the covering  102  is smaller than minimum dimensions, such as a minimum width of the feedstock  104 , such that the feedstock  104  is unable to pass through the openings  204 . The feedstock  104  is directed towards and sprayed onto the component  101 , through the thermal spraying nozzle  103 . The smaller area of the opening  204  in the covering  102  prevents the feedstock  104  from passing through the covering  102 . In one embodiment, the pattern of the interwoven fibers  203  in the mesh forms the openings  204  in the covering  102 . In another embodiment, the openings  204  in the covering  102  are formed by machining of the covering  102 . 
     Suitable dimensions of the opening  204  correspond to a particle size of the feedstock  104 . In one embodiment, the dimensions are, for example, less than 50 μm, between approximately 3 μm and approximately 50 μm, between approximately 3 μm and approximately 5 μm, between approximately 45 μm and approximately 55 μm, or any combination, sub-combination, range, or sub-range thereof. 
     Thermal spraying melts the feedstock  104  and forms molten droplets having a predetermined dimension. The molten droplets are accelerated towards and contact the component  101 . The molten droplets flatten upon contact with the component  101 . Suitable predetermined dimensions of the feedstock  104  include, but are not limited to, between approximately 2 μm and approximately 50 μm, between approximately 5 μm and approximately 45 μm, between approximately 15 μm and approximately 35 μm, between approximately 2 μm and approximately 30 μm, between approximately 2 μm and approximately 10 μm, between approximately 5 μm and approximately 15 μm, between approximately 10 μm and approximately 20 μm, between approximately 20 μm and approximately 30 μm, between approximately 30 μm and approximately 40 μm, between approximately 40 μm and approximately 50 μm, or any combination, sub-combination, range, or sub-range thereof. 
     Referring to  FIG. 3 , the thermal spraying of the feedstock  104  forms a coating  304  over the component  101 . In one embodiment, the covering  102  forms a continuous layer  401  ( FIG. 4 ) between the component  101  and the coating  304 , as is shown in section A-A of  FIG. 4 . In one embodiment, the covering  102  forms a discontinuous layer between the component  101  and the coating  304 , as is shown in  FIG. 1 . The covering  102  is melted, decomposed, oxidized, microstructurally modified, destroyed by the thermal spraying, maintained intact, or other suitable combinations thereof. The covering  102  may no longer be present as a defined layer between the component  101  and the coating  304 , may remain as a separate layer between the component  101  and the coating  304 , or any suitable combination thereof. 
     The component  101  is any suitable article or portion of an article, for example, an airfoil, a cooling fin, a finger, a hot-gas-path member, or a combination thereof. Hot-gas-path members are gas turbine members exposed to a combustion process and/or to hot gases discharged from a combustion reaction. Suitable hot-gas-path members include, but are not limited to, a combustion liner, an end cap, a fuel nozzle assembly, a crossfire tube, a transition piece, a turbine nozzle, a turbine stationary shroud, a turbine bucket (blade), turbine disks, turbine seals, or a combination thereof. In one embodiment, the component  101  is capable of withstanding harsh conditions, for example, temperatures of between about 1500° F. and about 2600° F., between about 1500° F. and about 2100° F., between about 2100° F. and about 2600° F., between about 1800° F. and about 2300° F., between about 2000° F. and about 2400° F., or any suitable range, sub-range, combination, or sub-combination thereof. 
     To prevent heat damage to the component  101 , in one embodiment, the cooling channel  105  is provided on a surface  107  of the component  101 . In a further embodiment, the cooling channel  105  includes a cooling fluid such as, but not limited to, a gas, a liquid, a refrigerant, or a combination thereof. Suitable embodiments of the cooling channel  105  include, but are not limited to, semi-circular, rectangular, triangular, linear, curved, complex, intersecting, parallel, or a combination thereof. The covering  102  prohibits the feedstock  104  from entering the cooling channel  105  during thermal spraying, causing the coating  304  to form over the cooling channel  105  and the covering  102 . The coating  304  over the cooling channel  105  prohibits the cooling fluid from escaping the cooling channel  105 . 
     A thickness of the coating  304  over the cooling channels  105  controls a heat transfer rate of the cooling medium. A decrease in the thickness of the coating  304  increases a cooling rate of the cooling channel  105 . Suitable thicknesses of the coating  304  include, but are not limited to, between approximately 150 μm and approximately 4,000 μm, between approximately 300 μm and approximately 1,000 μm, between approximately 200 μm and approximately 800 μm, between approximately 150 μm and approximately 250 μm, between approximately 500 μm and approximately 1,500 μm, or any combination, sub-combination, range, or sub-range thereof. 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.