Patent Publication Number: US-2016237822-A1

Title: Blade restoration using shroud plating

Description:
BACKGROUND 
     Surfaces (e.g., hardface notch surfaces) of shrouded turbine blades have the potential to wear during engine operation. In order to maintain such blades in service, or to restore such blades following maintenance, very strict tolerances need to be adhered to in order to ensure operability and performance. In order to machine the surfaces to such tolerances, a machining fixture locates/positions onto the blade&#39;s outer shroud faces. These outer shroud locating faces can wear during engine operation and can lose dimension/material during cleaning and coating strip operations. Conventional techniques to restore these shroud faces include subjecting the shroud faces to a tungsten inert gas (TIG) welding, a plasma welding, or a laser welding. However, the application of such techniques can lead to Heat Affected Zone (HAZ) cracks in a base material of the blade. 
     BRIEF SUMMARY 
     The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. The summary is not an extensive overview of the disclosure. It is neither intended to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure. The following summary merely presents some concepts of the disclosure in a simplified form as a prelude to the description below. 
     Aspects of the disclosure are directed to a method comprising: applying a plating solution to a base material of a notch associated with a shroud section of a turbine blade, and applying an electrical signal to the plating solution to cause a deposition of material onto the base material to faint a composite. In some embodiments, the notch is substantially z-shaped. In some embodiments, the notch is composed of a center segment and two outer segments. In some embodiments, the solution comprises a nickel-cobalt matrix. In some embodiments, the solution comprises a powder. In some embodiments, the powder is less than twenty-two microns in dimension. In some embodiments, the powder is of the base material. In some embodiments, the method further comprises applying a source of heat to the composite to facilitate diffusion binding to the base material. In some embodiments, the method further comprises applying a coating to the turbine blade. In some embodiments, the method is performed as part of a scheduled engine service. In some embodiments, the method is performed to restore material associated with the notch due to wear. In some embodiments, less than 0.020 inches of material is deposited onto the base material. In some embodiments, the turbine blade is associated with a low pressure turbine section of a turbine of an aircraft engine. 
     Aspects of the disclosure are directed to a shroud section associated with a turbine blade, comprising: a composite material deposited onto a base material of a notch of the shroud section based on an application of an electrical signal to a plating solution. In some embodiments, the notch is substantially z-shaped. In some embodiments, the notch is composed of a center segment and two outer segments. In some embodiments, the solution comprises a nickel-cobalt matrix. In some embodiments, the solution comprises a powder. In some embodiments, the powder is less than twenty-two microns in dimension. In some embodiments, the powder is of the base material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements. 
         FIG. 1  is a side cutaway illustration of a geared turbine engine. 
         FIG. 2  illustrates an exemplary blade assembly. 
         FIG. 3  illustrates a portion of a shroud associated with the assembly of  FIG. 2 . 
         FIG. 4  illustrates a flow chart of an exemplary method for restoring a blade or shroud. 
     
    
    
     DETAILED DESCRIPTION 
     It is noted that various connections are set forth between elements in the following description and in the drawings (the contents of which are included in this disclosure by way of reference). It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. 
     In accordance with various aspects of the disclosure, apparatuses, systems and methods are described for restoring a blade using a plating technique. In some embodiments, a thick plating is used, potentially instead of welding, to build-up shroud surfaces that can be machined to close tolerances. The build-up of plating may be equal to, or less than, approximately 0.020 inches (approximately 0.50 millimeters). 
       FIG. 1  is a side cutaway illustration of a geared turbine engine  10 . This turbine engine  10  extends along an axial centerline  12  between an upstream airflow inlet  14  and a downstream airflow exhaust  16 . The turbine engine  10  includes a fan section  18 , a compressor section  19 , a combustor section  20  and a turbine section  21 . The compressor section  19  includes a low pressure compressor (LPC) section  19 A and a high pressure compressor (RPC) section  19 B. The turbine section  21  includes a high pressure turbine (HPT) section  21 A and a low pressure turbine (LPT) section  21 B. 
     The engine sections  18 - 21  are arranged sequentially along the centerline  12  within an engine housing  22 . Each of the engine sections  18 - 19 B,  21 A and  21 B includes a respective rotor  24 - 28 . Each of these rotors  24 - 28  includes a plurality of rotor blades arranged circumferentially around and connected to one or more respective rotor disks. The rotor blades, for example, may be formed integral with or mechanically fastened, welded, brazed, adhered and/or otherwise attached to the respective rotor disk(s). 
     The fan rotor  24  is connected to a gear train  30 , for example, through a fan shaft  32 . The gear train  30  and the LPC rotor  25  are connected to and driven by the LPT rotor  28  through a low speed shaft  33 . The HPC rotor  26  is connected to and driven by the HPT rotor  27  through a high speed shaft  34 . The shafts  32 - 34  are rotatably supported by a plurality of bearings  36 ; e.g., rolling element and/or thrust bearings. Each of these bearings  36  is connected to the engine housing  22  by at least one stationary structure such as, for example, an annular support strut. 
     During operation, air enters the turbine engine  10  through the airflow inlet  14 , and is directed through the fan section  18  and into a core gas path  38  and a bypass gas path  40 . The air within the core gas path  38  may be referred to as “core air”. The air within the bypass gas path  40  may be referred to as “bypass air”. The core air is directed through the engine sections  19 - 21 , and exits the turbine engine  10  through the airflow exhaust  16  to provide forward engine thrust. Within the combustor section  20 , fuel is injected into a combustion chamber  42  and mixed with compressed core air. This fuel-core air mixture is ignited to power the turbine engine  10 . The bypass air is directed through the bypass gas path  40  and out of the turbine engine  10  through a bypass nozzle  44  to provide additional forward engine thrust. This additional forward engine thrust may account for a majority (e.g., more than 70 percent) of total engine thrust. Alternatively, at least some of the bypass air may be directed out of the turbine engine  10  through a thrust reverser to provide reverse engine thrust. 
     The engine  10  is illustrative. Aspects of the disclosure may be applied in connection with other engine types or configurations. 
     Referring now to  FIG. 2 , an example of a blade system assembly  200  is shown. The assembly  200  may be applied in connection with one or more of the components or devices of the engine  10  of  FIG. 1 . For example, the assembly  200  may be applied in connection with the turbine section  21 . 
     The assembly includes a disk  202 , a base  204 , a plurality of blades  206 , and a shroud  208 . The disk  202  may be a statically or dynamically balanced unit comprised of one or more materials, such as for example steel, chromium, nickel, or cobalt, or alloys thereof. The blades  206  may be attached to the disk  202  via a “fir tree” design geometry incorporated in the base  204  to allow for different rates of expansion between the disk  202  and the blades  206 , while still holding/retaining the blades  206  when the assembly  200  (e.g., the blades  206 ) is subjected to loading. The shroud  208  may form a band around the perimeter of the turbine section  21  and may help to minimize/reduce blade  206  vibrations. The shroud  208  may enhance airflow characteristics and increase the efficiency of the turbine section  21 . The shroud  208  may serve to minimize/reduce leakage around the tips of the blades  206 . 
     The assembly  200  is illustrative. In accordance with aspects of the disclosure, different types or configurations of blade assemblies may be used. Moreover, while eight blades  206  are shown, embodiments may include a different number of blades. For example, embodiments may include, e.g., one-hundred fifty blades  206 . 
     A portion of the shroud  208  (associated with the blades  206 ) is shown in  FIG. 3 . As shown in  FIG. 3 , the shroud may be composed of one or more sections, such as for example sections  208 - 1  through  208 - 3 . A given section (e.g., the section  208 - 2 ) may be associated with a given blade  206 . 
     The sections  208 - 1  through  208 - 3  may be manufactured to include a notch, such as notches  210  through  216 . As shown in  FIG. 3 , the notches  210 - 216  may be substantially z-shaped, composed of a center segment (e.g., segment  210 - 1 ) and two outer segments (e.g., segments  210 - 2  and  210 - 3 ). The notch  210  may overlap/mesh with the notch  212 . Similarly, the notch  214  may overlap/mesh with the notch  216 . This overlapping/meshing between notches may create a substantially continuous shroud  208  when the assembly  200  is fabricated/manufactured. 
     The surfaces of the notches, and for example the center-segments of the z-shaped notches  210 - 216  (e.g., the center segment  210 - 1 ), may include a hardface that may be subject to wear during use/operation of the engine  10 . Given the large number of blades  206  and shroud sections (e.g., sections  208 - 1  through  208 - 3 ) that are used, tight/narrow tolerances associated with the geometries of the notches  210 - 216  may need to be maintained in order to ensure proper or efficient engine operation/performance. Otherwise, if tight tolerances are not maintained then the multiplicative effects associated with using a large number of blades  206  may significantly degrade the engine performance. 
     Referring now to  FIG. 4 , a flow chart of a method  400  is shown. The method  400  may be used to restore a blade  206  and/or a shroud  208  to service. For example, the method  400  may be executed in order to restore notch surfaces to a state acceptable for use following wear. 
     In step  402 , an application of a plating solution (e.g., a nickel-cobalt matrix) to a base material (e.g., a base material associated with a blade  206  or shroud  208 , such as a nickel alloy) may be provided. The solution may include a fine (e.g., less than twenty-two microns in size/dimension) powder of, e.g., the base material. Application of a signal (e.g., an electric current) to the solution in step  404  may (ultimately) cause a deposition or plating of material (e.g., the powder) onto the base material, thereby serving to restore any of the base material that may be absent due to the wear described above. Performance of the steps  402  and  404  may corresponding to a plating technique (e.g., an entrapment technique or electroplating technique). 
     Application of a source of heat to the composite (e.g., the combination of the plated powder on the base material) in step  406  may be included as part of the technique/method  400 . Application of the source of heat in step  406  may cause the method  400  to take-on characteristics of brazing or welding, which is to say that plating techniques may be combined with aspects of brazing or welding in some embodiments. In some embodiments, the application of heat in step  406  may facilitate diffusion binding to a base material or base alloy. 
     In step  408 , one or more coatings are applied. For example, one or more coatings may be applied to a component, such as a blade  206 . The coatings may include an environmental coating. 
     The steps associated with the method  400  may be executed in an order or sequence that is different from what is shown in  FIG. 4 . In some embodiments, one or more of the steps may be optional. In some embodiments, additional steps not shown may be included. 
     The method  400  may be performed in accordance with scheduled or periodic engine service. The method  400  may be performed as part of unscheduled engine service. 
     Technical effects and benefits of this disclosure include an enhanced maintenance/repair technique that does not require shroud faces of a blade to be welded. Accordingly, the structural strength/integrity of a base metal associated with the blade may be maintained. A plating material that is used may be compatible with coatings that may be applied to the blade and may minimize/reduce the impact of environmental factors (e.g., temperature, humidity, etc.) on the blade. 
     Aspects of the disclosure have been described in terms of illustrative embodiments thereof. Numerous other embodiments, modifications, and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure. For example, one of ordinary skill in the art will appreciate that the steps described in conjunction with the illustrative figures may be performed in other than the recited order, and that one or more steps illustrated may be optional in accordance with aspects of the disclosure. One or more features described in connection with a first embodiment may be combined with one or more features of one or more additional embodiments.