Abstract:
A system and a method for electroplating a plurality of turbine blades, comprising providing a rotatable gear for each blade, operatively connecting a mount assembly for each gear, slidably placing an electric charge on the blades.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority of Singapore Patent Application No. 200701366-7, filed on Feb. 27, 2007, and entitled “SYSTEM AND METHOD FOR ELECTROPLATING METAL COMPONENTS”. 
     BACKGROUND 
     The present invention relates to systems and methods for electroplating metal components, such as aerospace components. In particular, the present invention relates to systems and methods for rotating metal components during electroplating processes, thereby improving the uniformity of plated metal coatings. 
     Gas turbine engine components (e.g., turbine blades and vanes) are exposed to extreme temperatures and pressures during the course of operation. Such components are typically electroplated with metal coatings to protect the underlying components during operation. Electroplating techniques typically involve placing the engine component in a bath of a plating solution, and inducing a current through the engine component and the plating solution. The current causes positive-charged metallic ions of the plating solution to deposit onto the negatively-charged engine components, thereby forming plated metal coatings. 
     The uniformity of a plated metal coating (e.g., thickness and density) is important to properly protect an underlying component. As a result, electroplating processes typically require continuous monitoring and adjustments to ensure that uniform metal coatings are formed on the engine components. Such monitoring and adjustments are tedious and cumbersome to perform. Thus, there is a need for a system and method for electroplating metal components that are easy to use and provide substantially uniform metal coatings. 
     SUMMARY 
     The present invention relates to a system and method for electroplating a metal component. The system includes a rotatable gear, a mount assembly secured to the gear for retaining the metal component, and a conductive contact secured for placing electric charge on the retained metal component during an electroplating process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an electroplating system of the present invention, showing a rotator assembly disposed above a plating bath. 
         FIG. 2  is an expanded perspective view of the rotator assembly of the electroplating system. 
         FIG. 3  is an expanded front view of a portion of the rotator assembly, showing the interconnections of a gear assembly and a cathode assembly of the rotator assembly. 
         FIG. 4  is an expanded front view of a portion of an alternative rotator assembly for retaining multiple blades. 
         FIG. 5  is a flow diagram of a method for performing an electroplating process on a metal component with a system that rotates the metal components. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective view of system  10 , which is an electroplating system that includes rotator assembly  12  and plating bath  14 , where rotator assembly  12  is disposed above plating bath  14 . As shown, rotator assembly  12  retains blades  16   a - 16   d , and includes frame  18 , motor  20 , gear assembly  22 , and cathode assembly  24 . Blades  16   a - 16   d  are turbine blades undergoing an electroplating process to receive a plated metal coating. While system  10  is particularly suitable for electroplating turbine engine components (e.g., turbine blades and vanes), system  10  may be used with any metal component that requires an electroplated metal coating. 
     Frame  18  of rotator assembly  12  includes support arms  26  and base platform  28  secured to support arms  26 . Base platform  28  is desirably formed from a non-conductive material (e.g., plastics) to electrically isolate cathode assembly  24  from motor  20  and support arms  26 . As used herein, the term “conductive” refers to electrical conductivity. Frame  18  desirably allows rotator assembly  12  to be lowered and raised, thereby respectively immersing and removing blades  16   a - 16   d , into and from, plating bath  14 . In alternative embodiments, frame  18  may include different structural components that allow rotator assembly  12  to be raised and lowered, manually or in an automated manner, relative to plating bath  14 . 
     Motor  20  is a drive motor for operating gear assembly  22 . As discussed below, gear assembly  22  is mounted on base platform  28 , and blades  16   a - 16   d  are mounted to gear assembly  22  such that blades  16   a - 16   d  extend below base platform  28 . Accordingly, the operation of gear assembly  22  via motor  20  rotates blades  16   a - 16   d  during an electroplating process. This allows a metal coating having a substantially uniform thickness and density to be formed on each of blades  16   a - 16   d.    
     Cathode assembly  24  is a conductive contact portion of rotator assembly  12 , and is supported by gear assembly  22 . Cathode assembly  24  is also conductively connected to blades  16   a - 16   d  when blades  16   a - 16   d  are mounted to gear assembly  22 . During an electroplating process, cathode assembly  24  is also connected to a negative terminal of a battery or other direct-current (DC) source (not shown), thereby placing a negative charge on cathode assembly  24 . This correspondingly places negative charges on blades  16   a - 16   d . Suitable alternative DC sources include controllers that provide continuous plating currents or pulsed DC currents. 
     Plating bath  14  includes bath container  30 , plating solution  32 , and anode mesh  34 , where bath container  30  is a fluid-holding structure that contains plating solution  32  and anode mesh  34 . Plating solution is a metal-salt solution containing a metal used for an electroplating process. The particular metal used depends on the desired plated metal coating that will be formed on blades  16   a - 16   d . Examples of suitable electroplating metals include platinum, silver, nickel, cobalt, copper, aluminum, and combinations thereof, with particularly suitable electroplating metals for turbine engine components including platinum and aluminum. As used herein, the term “solution” refers to any suspension of particles in a carrier fluid (e.g., water), such as dissolutions, dispersions, emulsions, and combinations thereof. 
     Anode mesh  34  is a conductive metal wall that is connected to a positive terminal of a battery or other DC source (not shown), thereby placing a positive charge within plating solution  32  during an electroplating process. As discussed above, suitable alternative DC sources include controllers that provide continuous plating currents or pulsed DC currents. In alternative embodiments, plating bath  14  may include two or more anode walls, which further distribute the positive charge within plating solution  32 . For example, a second anode mesh (not shown) may be disposed parallel to anode mesh  34  adjacent the opposing wall of bath container  30 . Furthermore, an additional anode mesh (not shown) may be disposed on the bottom of bath container  30 , perpendicular to the pair of parallel anode meshes. Many other arrangements of anode mesh  34  are also possible. 
     During an electroplating process, blades  16   a - 16   d  are mounted to gear assembly  22  of rotator assembly  12 , below base platform  28 . Rotator assembly  12  is then lowered down toward plating bath  14  (in the direction of arrow  36 ) until blades  16   a - 16   d  are at least partially immersed in plating solution  32 . Rotator assembly  12  is desirably lowered until base platform  28  is disposed at the surface of, or partially immersed in, plating solution  32 . This fully immerses blades  16   a - 16   d  within plating solution  32 , while also preventing the components above base platform  28  (e.g., gear assembly  22  and cathode assembly  24 ) from being immersed. 
     After blades  16   a - 16   d  are immersed, motor  20  then causes gear assembly  22  to continuously rotate blades  16   a - 16   d  within plating solution  32 . A negative charge is then placed on cathode assembly  24  and a positive charge is placed on anode mesh  34 . Because blades  16   a - 16   d  are in conductive contact with cathode assembly  24 , negative charges are also placed on blades  16   a - 16   d . The positive charge placed on anode mesh  34  causes the metal-salts of plating solution  32  to disassociate, thereby forming positive-charged metallic ions in the carrier fluid. The negative charge placed on blades  16   a - 16   d  attracts the metallic ions, and reduces the positive charges on the metallic ions upon contact with blades  16   a - 16   d . This forms metal coatings bonded to blades  16   a - 16   d.    
     As shown in  FIG. 1 , anode mesh  34  is disposed adjacent the rear side of bath container  30 . As such, when rotator assembly  12  is lowered toward plating bath  14 , anode mesh  34  is correspondingly disposed adjacent one side of the immersed blades  16   a - 16   d . If blades  16   a - 16   d  remained motionless (i.e., non-rotated), a greater amount of metallic ions would deposit onto the surfaces of blades  16   a - 16   d  that face anode mesh  34  compared to the surfaces that do not face anode mesh  34 . This would result in non-uniform coatings formed on blades  16   a - 16   d , which may reduce the effectiveness of the resulting metal coatings. 
     In contrast, the rotational motion applied to blades  16   a - 16   d  by rotator assembly  12  evenly distributes the amount of time each surface of each blade faces anode mesh  34 . This increases the uniformity of the plated metal coatings formed on blades  16   a - 16   d  without requiring manual monitoring or adjustments. Additionally, system  10  allows multiple metal components (e.g., blades  16   a - 16   d ) to be plated in a single electroplating process, thereby reducing the throughput time required to manufacture the metal components. 
       FIG. 2  is an expanded view of rotator assembly  12 , further illustrating gear assembly  22  and cathode assembly  24 . As shown, gear assembly  22  includes reducing gear  38  and blade-rotating gears  40   a - 40   d . Reducing gear  38  is a rotatable gear axially connected to motor  20 , which allows motor  20  to rotate reducing gear  38 . Reducing gear  38  also engages gear  40   d , thereby allowing reducing gear  38  to correspondingly rotate gear  40   d  when motor  20  rotates reducing gear  38 . 
     Gears  40   a - 40   d  are a series of engaged rotatable gears, which allows a given gear in the series (e.g., gear  40   b ) to be driven by the previous gear in the series (e.g., gear  40   c ), and also allows the given gear to drive the successive gear in the series (e.g., gear  40   a ). Consequentially, reducing gear  38  provides rotational power to rotate each gear of gears  40   a - 40   d , as represented by the rotational arrows on reducing gear  38  and gears  40   a - 40   d . This correspondingly rotates blades  16   a - 16   d  in the same rotational directions as gears  40   a - 40   d , respectively. Alternatively, motor  20  may rotate reducing gear  38  in an opposite rotational direction, thereby rotating gears  40   a - 40   d  and blades  16   a - 16   d  in opposite rotational directions from those shown in  FIG. 2 . 
     Blades  16   a - 16   d  rotate at about the same rotational speeds because gears  40   a - 40   d  have about the same diameters. Examples of suitable rotational speeds for gears  40   a - 40   d  and blades  16   a - 16   d  range from about 10 rotations-per-minute (rpm) to about 40 rpm, with particularly suitable rotational speeds ranging from about 20 rpm to about 25 rpm. In alternative embodiments, one or more gears in the series (e.g., gears  40   a - 40   d ) may have different diameters from other gears in the series. In these embodiments, the gears having smaller diameters rotate at higher rotational speeds compared to the larger-diameter gears. As such, during an electroplating process, one or more of the metal components (e.g., turbine blades and vanes) may be rotated at different rotational speeds from the other metal components. This increases the versatility of system  10 , and allows users to customize the electroplating process. 
     Reducing gear  38  and gears  40   a - 40   d  are desirably formed from non-conductive material (e.g., plastics) to further electrically isolate cathode assembly  24  from motor  20  and support arms  26 . While gear assembly  22  is shown with four blade-rotating gears (i.e., gears  40   a - 40   d ), rotator assembly  12  may include fewer or additional numbers of metal component-rotating gears. The number of gears that may be used is generally dictated by the size and capacity of plating bath  14  (shown in  FIG. 1 ). Examples of suitable numbers of metal component-rotating gears for rotator assembly  12  range from one gear to 20 gears. In another alternative embodiment, one or more of the gears in the series (e.g., gears  40   a - 40   d ) may be rotated directly from motor  20 , thereby omitting the need for reducing gear  38 . 
     Cathode assembly  24  includes cathode contacts  42   a - 42   d , current connector  44 , and battery contact  46 . Cathode contacts  42   a - 42   d  are conductive metal shafts that extend axially through gears  40   a - 40   d , respectively. Cathode contacts  42   a - 42   d  are the portions of cathode assembly  24  that are in conductive contact with blades  16   a - 16   d , respectively. Current connector  44  is a conductive metal plate that interconnects cathode contacts  42   a - 42   d  to increase the distribution of current between cathode contacts  42   a - 42   d . In alternative embodiments, current connector  44  may be provided in other designs that provide conductive interconnections, such as chain links and wire meshes. One or more portions of cathode assembly  24  may also be encased in an electrically insulating container or wrapping to reduce the risk of shorting cathode assembly  24  during operation. 
     In the embodiment shown in  FIG. 2 , battery contact  46  is a conductive metal pad secured to current connector  44 , which provides a convenient location to connect cathode assembly  24  to a negative terminal of a battery or other DC source (not shown). In alternative embodiments, battery contact  46  may be integrally formed with current connector  44  instead of being a separate piece of conductive material attached to current connector  44 . When the negative terminal of a battery/DC source is connected to battery contact  46 , the negative charge is applied to cathode contacts  42   a - 42   d  via current connector  44 . This correspondingly places negative charges on the rotating blades  16   a - 16   d  for attracting positive-charged metallic ions during an electroplating process. As discussed above, rotating blades  16   a - 16   d  during the electroplating process increases the uniformity of the plated metal coatings formed on blades  16   a - 16   d . Accordingly, gear assembly  22  and cathode assembly  24  provide a convenient and efficient means for rotating and placing negative charges on blades  16   a - 16   d  during the electroplating process. 
       FIG. 3  is an expanded front view of rotator assembly  12 , further illustrating the interconnections between gear  40   b  and cathode contact  42   b . While the following discussion refers to gear  40   b  and cathode contact  42   b , the discussion also applies to any blade-rotating gear and conductive contact of rotator assembly  12  (e.g., gears  40   a - 40   d  and conductive contacts  42   a - 42   d ). As shown in  FIG. 3 , gear assembly  22  further includes bearings shaft  48 , collar  50 , retention pin  52 , and mount assembly  54 . Bearings shaft  48  extends through gear  40   b  and into base platform  28 , thereby allowing base platform  28  to support bearings shaft  48 . Bearings shaft  48  includes a set of bearings (not shown) that stabilize the rotation of gear  40   b  and blade  16   b.    
     Collar  50  is a ring-like component integrally formed with gear  40   b , which extends around bearings shaft  48  below gear  40   b . Collar  50  is supported by bearings shaft  48  with retention pin  52 , where retention pin  52  extends through bearings shaft  48  and collar  50 . As such, gear  40   b  is vertically supported by bearings shaft  48 , and the rotation of gear  40   b  correspondingly rotates bearings shaft  48 . This arrangement allows gear  40   b  to be removed from bearings shaft  48  (by removing retention pin  52 ) for maintenance and cleaning. In an alternative embodiment, collar  50  is a separate component that is secured to gear  40   b.    
     Mount assembly  54  is a conductive metal component that includes mount shaft  56  and mount block  58 , where mount block  58  may be integrally formed with mount shaft  56 . Mount shaft  56  is secured to bearings shaft  48  at a location within base platform  28 , thereby allowing the rotation of bearings shaft  48  (via gear  40   b ) to also rotate mount assembly  54 . Mount block  58  is the portion of gear assembly  24  that retains blade  16   b  during an electroplating process. 
     Blade  16   b  (shown with broken lines) includes airfoil  60  and blade root  62 , where airfoil  60  extends from blade root  62 . Blade  16   b  is retained by mount assembly  54  by sliding at least a portion of blade root  62  (referred to as portion  64 ) into mount block  58  (in the direction of arrow  66 ) until portion  64  is disposed within mount block  58 . In one embodiment, mount block  58  includes a locking mechanism (not shown) to securely retain blade  16   b  during an electroplating process. While blade  16   b  is retained by mount assembly  54 , the rotation of mount assembly  54  (via gear  40   b  and bearings shaft  48 ) correspondingly rotates blade  16   b.    
     After blade  16   b  is inserted onto mount assembly  54 , one or more portions of blade  16   b  may be masked to prevent the plated metallic coating from being formed on masked portions. For example, the exposed portion of root  62  may be masked to prevent the plated metallic coating from being formed on root  62 . After the electroplating process is complete, blade  16   b  may be removed from mount assembly  54  by sliding root  62  out of mount block  58 . Accordingly, mount assembly  54  provides a convenient arrangement for easily inserting and removing metal components between electroplating process. 
     As further shown in  FIG. 3 , cathode contact  42   b  includes conductive shaft  68  and retention nut  70 . Conductive shaft  68  extends through current connector  44 , bearings shaft  48 , gear  40   b , and base platform  28 , and is secured to bearings shaft  48 . Conductive shaft  68  also extends down within base platform  28  to contact mount shaft  56 . This provides a conductive connection between current connector  44  and mount assembly  54  to place a negative charge on mount assembly  54 . In an alternative embodiment, conductive shaft  68  is integrally formed with mount shaft  56 . Retention nut  70  is secured to conductive shaft  68 , thereby retaining current connector  44  around conductive shaft  68 , between bearings shaft  48  and retention nut  70 . 
     During operation, blade  16   b  is inserted onto mount block  58  and rotator assembly  12  is lowered into plating bath  14  (shown in  FIG. 1 ). Because gear  40   b  and cathode contact  42   b  are disposed primarily on the top side of base platform  28 , and mount assembly  54  and blade  16   b  are disposed on the bottom side of base platform  28  (i.e., adjacent opposing major surfaces of base platform  28 ), blade  16   b  may be immersed into plating bath  14  without immersing gear  40   b  and cathode contact  42   b . Thus, base platform  28  provides a physical structure that prevents plating solution  32  (shown in  FIG. 1 ) from contacting immersing gear  40   b  and cathode contact  42   b.    
     Gears  40   a - 40   d  are then rotated by motor  20  (shown in  FIGS. 1 and 2 ) and reducing gear  38  (shown in  FIGS. 1 and 2 ). This causes gear  40   c  to rotate gear  40   b  due to the gear engagement at intersection  64 . The rotation of gear  40   b  correspondingly rotates gear  40   a  due to the gear engagement at intersection  66 . The rotation of gear  40   b  also rotates collar  50  and bearings shaft  48  (due to retention pin  52 ), which correspondingly rotates mount assembly  54  and blade  16   b . While gear  40   b  is rotating, a negative charge is placed on conductive shaft  68  via current connector  44 . Due to the conductive connections, the negative charge is thereby placed on bearings shaft  48 , mount assembly  54 , and blade  16   b . Thus, this arrangement of gear assembly  22  and cathode assembly  24  allows blades  16   a - 16   d  to rotate and receive negative charges in a simultaneous manner. 
       FIG. 4  is an expanded front view of rotator assembly  112 , which is an alternative embodiment to rotator assembly  12  (shown in  FIGS. 1-3 ). Rotator assembly  112  has a configuration similar to rotator assembly  12 , and the respective reference labels are increased by 100. In this embodiment, mount assembly  54  of rotator assembly  12  is replaced with mount assembly  172 , which allows multiple blades (e.g., blades  174  and  176  shown in  FIG. 4 ) to be rotated with a single gear (e.g., gear  140   b ). Mount assembly  172  is a conductive metal component that includes mount shaft  178 , extension members  180   a  and  180   b , and mount blocks  182   a  and  182   b . Extension members  180   a  and  180   b  are a pair of opposing arms interconnecting mount shaft  178  and mount blocks  182   a  and  182   b . Mount shaft  178  is secured to bearings shaft  148  at a location within base platform  128 , thereby allowing the rotation of bearings shaft  148  (via gear  140   b ) to also rotate extension members  180   a  and  180   b  and mount blocks  182   a  and  182   b . Mount blocks  182   a  and  182   b  are the portions of gear assembly  124  that respectively retain blades  174  and  176  during an electroplating process. 
     Rotator assembly  112  may be used in an electroplating process in the same manner as discussed above for rotator assembly  12 , where gear  140   b  rotates both blades  174  and  176 . This arrangement allows a greater number of blades to be plated during a single electroplating process. While mount assembly  172  is shown with two extension members  180   a  and  180   b  and two mount blocks  182   a  and  182   b  (for retaining two blades  174  and  176 ), mount assembly  172  may alternatively include additional extension members and mount blocks for retaining an even greater number of blades. For example, mount assembly  172  may include four extension members and four mount blocks, which form a cross pattern from mount shaft  178 , thereby allowing four blades to be retained from gear  140   b . This further increases the number of blades that may be plated during a single electroplating process. Many other arrangements of multiple metal components for each mount assembly are also possible. 
       FIG. 5  is a flow diagram of method  200  for performing an electroplating process on one or more metal components with an electroplating system that rotates the metal components, such as system  10 . Method  200  includes steps  202 - 212 , and initially involves inserting one or more metal components (e.g., blades  16   a - 16   d ) onto rotatable mounts (step  202 ). Preferably, multiple metal components are inserted onto multiple rotatable mounts to increase the throughput of the electroplating process. One or more portions of the metal components are then optionally masked to prevent plated metallic coatings from being deposited on the masked portions (step  204 ). In alternative embodiments, the metal components may be masked prior to being inserted onto the rotatable mounts. The metal components are then immersed in a plating solution containing metal salts of the metal to be electroplated on the metal components (step  206 ). 
     The immersed metal components are then rotated (step  208 ). Each metal component is desirably rotated such that the surfaces of the given metal component face a plating bath anode for substantially the same durations. Suitable rotation speeds for the metal components include those discussed above for blades  16   a - 16   d . In an alternative embodiment, steps  206  and  208  are performed in an opposite order, where the metal components are rotating prior to being immersed in the plating solution. 
     The immersed, rotating metal components are then electroplated to form metal coatings on the exposed surfaces of the metal components (step  210 ). This involves placing negative charges on the metal components and a positive charge on the plating anode. As discussed above, the positive charge placed on the plating anode causes the metal salts of the plating solution to disassociate to form positive-charged metallic ions. The metallic ions are attracted to the negative-charged surfaces of the rotating metal components, thereby forming metal coatings on the metal components. 
     The electroplating process is performed for a duration, and with a plating current magnitude, sufficient to form metal coatings of desired thicknesses on the metal components. Examples of suitable processing conditions include a duration ranging from about one hour to about two hours at a plating current ranging from about 0.1 amperes to about 0.5 amperes, with particularly suitable processing conditions including a duration of about 180 minutes at a plating current of about 0.22 amperes. When the desired metal coatings are formed, the negative and positive charges are removed from the metal components and the plating bath anode, respectively, and the metal components are removed from the plating solution (step  212 ). The resulting metal components may then undergo post-processing cleaning and dryings steps. Rotating the metal components during the electroplating process increases the uniformity of the deposited metal coatings without requiring manual monitoring or adjustments. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.