Abstract:
A coating process and coated article are provided. The coating process includes providing a turbine component, applying a coating repellant to a predetermined region of the turbine component, and depositing a coating material on the turbine component. The coating repellant directs the coating material away from the predetermined region of the turbine component, to at least partially form a channel. A coating process for a hot gas path turbine component and coated article are also disclosed.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to coating methods and coated articles for turbine components. More specifically, the present invention is directed to thermal barrier coating methods and thermal barrier coated articles for turbine component. 
       BACKGROUND OF THE INVENTION 
       [0002]    Temperature limitations of turbine component materials present a barrier to increasing turbine operation temperatures, and thus, turbine efficiency. Limitations on cooling capabilities of such turbine components is one feature that results in such temperature limitations. For example, a failure to adequately cool and/or operation at or above predetermined temperatures can translate into fatigue due to thermal expansion and contraction of the turbine components. 
         [0003]    In addition, turbine components are subject to a temperature profile having a temperature gradient. The temperature profile and/or the temperature gradient can heat different portions of a turbine component at different rates, especially during start-up or shut-down of operation. Such uneven heating can result in low-cycle fatigue, which is undesirable because it decreases the overall useful life of the turbine component. 
         [0004]    A formation of channels or trenches on a surface of the turbine component materials can provide additional cooling to the component. However, near-surface cooling channels can be difficult to form. Near-surface cooling channels can also form difficulties in repairing the turbine component. Additionally, a machining of trenches or channels extending through a coating to a base material can result in trenching and/or scarfing of a base metal. One method of forming trenches or channels extending through the coating to the base material includes using a water jet. Controlling the depth of the trench can be difficult with a water jet, often causing the trench to extend into the base material. Furthermore, machining of materials can result in undesirable features, such as, an inability to re-produce or repair components that have already been machined. 
         [0005]    A turbine component coating process and a coated turbine component that do not suffer from one or more of the above drawbacks would be desirable in the art. 
         [0006]    BRIEF DESCRIPTION OF THE INVENTION 
         [0007]    In an exemplary embodiment, a coating process includes providing a turbine component, applying a coating repellant to a predetermined region of the turbine component, and depositing a coating material on the turbine component. The coating repellant directs the coating material away from the predetermined region of the turbine component, to at least partially form a channel. 
         [0008]    In another exemplary embodiment, a coating process includes providing a hot gas path turbine component, applying an elongated strip of a coating repellant to a predetermined region of the hot gas path turbine component, depositing a coating material on the hot gas path turbine component, and removing the elongated strip of the coating repellant. The coating repellant directs the coating material away from the predetermined region of the hot gas path turbine component, forming a cooling channel in the hot gas path turbine component. 
         [0009]    In another exemplary embodiment, a coated article includes a turbine component, a bond coat over the turbine component, a thermal barrier coating over the bond coat, and a channel through the thermal barrier coating and the bond coat. The channel is formed during an application of the bond coat and thermal barrier coating, the channel exposing a substrate surface of the turbine component. 
         [0010]    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 
         [0011]      FIG. 1  is a perspective view of a turbine bucket having coating repellant, according to an embodiment of the invention. 
           [0012]      FIG. 2  is a perspective view of a turbine shroud having coating repellant, according to an embodiment of the invention. 
           [0013]      FIG. 3  is a cross-sectional view of multiple coating repellant strips, according to an embodiment of the invention. 
           [0014]      FIG. 4  is a cross-sectional view of a coating repellant strip, according to an embodiment of the invention. 
           [0015]      FIG. 5  is a cross-sectional view of a coating repellant strip, according to an embodiment of the invention. 
           [0016]      FIG. 6  is a cross-sectional view of a coating repellant strip, according to an embodiment of the invention 
           [0017]      FIG. 7  is a cross-sectional view of a coating repellant strip, according to an embodiment of the invention. 
           [0018]      FIG. 8  is a sectional view of a coating repellant in a channel, according to an embodiment of the invention. 
           [0019]      FIG. 9  is a sectional view of a coating repellant in a channel, according to an embodiment of the invention. 
           [0020]      FIG. 10  is a perspective view of a coating repellant in a channel, according to an embodiment of the invention. 
       
    
    
       [0021]    Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Provided is an exemplary turbine component coating method and coated turbine component. Embodiments of the present disclosure, in comparison to processes and articles not using one or more of the features disclosed herein, decrease trenching of a metal in a component, increase efficiency of channel formation, decrease cost of channel formation, increase control of channel formation, increase exposure of a substrate material, or a combination thereof. 
         [0023]    Referring to  FIG. 1  and  FIG. 2 , a coating repellant  101  is applied to a predetermined region  104  of a turbine component  105 . The predetermined region  104  includes a portion of a substrate surface  103 . The substrate surface  103 , as used herein, refers to an outermost face of the turbine component  105  prior to deposition of a coating material  102 . The turbine component  105  is any suitable turbine component that includes film cooling, for example, a bucket (or blade), a nozzle, a shroud, a near flowpath seal, a sidewall, a dovetail, or a combination thereof. Suitable materials of the turbine component  105  include, but are not limited to, a ceramic matrix composite, an alloy, a directionally solidified metal, a single crystal metal, an equiaxed grain metal, other suitable metal compositions, or a combination thereof 
         [0024]    Referring to  FIG. 1 , in one embodiment, the turbine component  105  is a hot gas path component such as, but not limited to, a bucket  110  (or blade), a nozzle, or a combination thereof. A suitable position for the predetermined region  104  of the turbine component  105 , includes, but is not limited to, a suction side  123 , a pressure side  122 , a leading edge  120 , a trailing edge  121 , a sidewall, a platform, or a combination thereof 
         [0025]    Referring to  FIG. 2 , in one embodiment, the turbine component  105  is a gas turbine component such as, but not limited to, a shroud  210 . The shroud  210  includes at least a tip portion  220 , a rear portion  221 , a first edge  222 , and a second edge  223 . 
         [0026]    Referring to  FIG. 1  and  FIG. 2 , the coating material  102  is deposited on the turbine component  105 . The coating repellant  101  directs the coating material  102  away from the predetermined region  104 , forming a channel  106  in the turbine component  105 . The channel  106  extends through the coating material  102  to the substrate surface  103 . Removal of the coating repellant  101  exposes the channel  106 . In one embodiment, the predetermined region  104  includes a pre-formed channel in the substrate surface  103  of the turbine component  105 . 
         [0027]    In one embodiment, cooling holes are machined in the substrate surface  103  exposed by the channel  106  after the coating repellant  101  has been removed. In one embodiment, the cooling holes are machined in the substrate surface  103 , then covered by the coating repellant  101 . The cooling holes are machined using any suitable machining method including, but not limited to, water jet machining, electrical discharge machining (EDM), electrochemical machining (ECM), laser drilling, or a combination thereof. In one embodiment, the coating repellant  101  is used for masking of the turbine component  105 . 
         [0028]    Referring to  FIG. 3 ,  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 7 , suitable geometries of the coating repellant  101  include, but are not limited to, elongated strips having geometric profiles resembling a rectangle, a circle  301 , a square  302 , a triangle  303 , an octagon, a quadrilateral  304 , or a combination thereof. The elongated strips of the coating repellant  101  are applied in the predetermined region  104 , over a length of the substrate surface  103 . Suitable structure of the coating repellant  101  includes, but is not limited to, rigid, flexible, twisted, curved, straight, dashed (for example interrupted/broken segments), or a combination thereof 
         [0029]    In one embodiment, the coating repellant  101  is a pre-formed material such as a wire, tube, strip, strand, plate, or combination thereof. The coating repellant  101  is attached to or rests on the substrate surface  103 . Controlling a size and/or shape of the coating repellant  101  provides increased control over a depth of the channel  106 . In one embodiment, the coating repellant  101  is applied to the predetermined regions  104  of the turbine component  105  and cured. Suitable curing methods of the coating repellant  101  include, but are not limited to, thermal, radiation such as electron beam (EB) or ultraviolet (UV), catalyst, or a combination thereof. In one embodiment, thermal curing includes heating the coating repellant  101  at 250° F. for 30 minutes. In general, suitable thermal curing temperatures include, but are not limited to, between about 100° F. and about 400° F., between about 150° F. and about 350° F., between about 200° F. and about 400° F., between about 200° F. and about 300° F., between about 225° F. and about 275° F., or any combination, sub-combination, range, or sub-range thereof. Suitable thermal curing durations include, but are not limited to, between about 10 minutes and about 60 minutes, between about 10 minutes and about 50 minutes, between about 20 minutes and about 40 minutes, between about 25 minutes and about 35 minutes, or any combination, sub-combination, range, or sub-range thereof. 
         [0030]    The coating repellant  101  includes any material suitable for repelling the coating material  102 . Suitable materials for the coating repellant  101  include, but are not limited to, elastomers, silicon-based compounds, or a combination thereof. One suitable material has a composition of between about 20% and about 30% methyl vinyl/di-methyl vinyl/vinyl terminated siloxane, between about 20% and about 30% vinyl silicone fluid, between about 15% and about 30% ground silica, between about 3% and about 9% silanol terminated PDMS, up to about 0.5% sodium alumino sulphosilicate, up to about 1% vinyl-tris(2-methoxy ethoxy)silane, up to about 1% titanium dioxide, up to about 2% precipitated silica, up to about 1% stoddard solvent, up to about 0.5% neodecanoic acid, rare earth salts, up to about 0.5% rare earth 2-ethylhexanoate, and up to about 0.2% magnesium ferrite. 
         [0031]    After curing, the coating repellant  101  is maintained in position until the coating repellant  101  is removed. In one embodiment, the coating repellant  101  is thermally or chemically removed using mechanisms including, but not limited to, leaching agents, releasing agents, releasing gels, solvents, heat, or combinations thereof. In one embodiment, the coating repellant  101  is partially or completely vaporized during deposition of the coating material  102 , such that at least a portion of the coating repellant is removed upon completion of the deposition. Removing the coating repellant  101  opens the channel  106  and exposes the substrate surface  103  without scarfing or cutting the substrate surface  103 . After removing the coating repellant  101 , the channel  106  permits cooling to the turbine component  105 , such as micro-channel cooling, near-wall cooling, and/or film cooling. 
         [0032]    In one embodiment, the coating material  102  includes one or more bond coat  402  layer(s) and one or more thermal barrier coating (TBC)  401  layer(s). Directing away of the bond coat  402  and/or the TBC  401  at least partially forms the channel  106  as the coating material  102  is deposited. Referring to  FIG. 8  (section A-A of  FIG. 1 ), in one embodiment, the coating repellant  101  extends away from the substrate surface  103 , forming a protruding portion  801 . The protruding portion  801  facilitates the removal of the coating repellant  101  by providing an increased area for physically grasping the coating repellant  101 . 
         [0033]    Referring to  FIG. 9  (section A-A of  FIG. 1 ), in one embodiment, the coating repellant  101  is substantially level with the coating material  102 . An exposed portion  501  of the bond coat  402  is formed from the directing away of the TBC  401  from the coating repellant  101 . In another embodiment, the exposed portion  501  of the bond coat  402  is covered by additional TBC  401  deposition. Covering the exposed portion  501  of the bond coat  402  decreases wear and/or degradation of the bond coat  402  during use of the turbine component  105 . Additionally, the shape, geometry, position, orientation, size, length, thickness, diameter, or combination thereof of the coating repellant  101  provides a shape of the channel  106 . See, for example,  FIG. 10 . 
         [0034]    In one embodiment, the bond coat  402  is deposited on the substrate surface  103  of the turbine component  105  while being directed away from the coating repellant  101 . In one embodiment, the TBC  401  is deposited and the bond coat  402  is not deposited on the substrate surface  103  of the turbine component  105 . Suitable compositions of the bond coat  402  include, but are not limited to, FeCrAlY, CoCrAlY, NiCrAlY, or a combination thereof 
         [0035]    In one embodiment, the TBC  401  is deposited on the bond coat  402  while being directed away from the coating repellant  101 . In one embodiment, the bond coat  402  is deposited and the TBC  401  is not deposited on the substrate surface  103  of the turbine component  105 . Suitable compositions of the TBC  401  include, but are not limited to, Y 2 O 3  stabilized ZrO 2 , any yttria stabilized zirconia, or a combination thereof. 
         [0036]    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.