Abstract:
A method of repairing a component having interconnected porosity applies a material to the area of the porosity through a cold deposition process. Components repaired by this method are also claimed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a method of depositing additional material at selected locations on a cast part to close an interconnected porosity. 
         [0002]    Many components are formed by casting for various applications. One application that generally utilizes a cast component is a fluid manifold for a gas turbine engine. The fluid manifold may be used for any number of fluids, e.g., fuel, oil, air, etc. The fluid manifold is generally cast of an aluminum alloy, but may also be cast titanium alloy or cast steel. At least some known castings generally contain porosity as a result of the casting process and generally are hot isostatically pressed to close or minimize the amount of porosity. The porosity of such known casting is generally open to outermost surfaces of the casting even with the hot isostatic pressing process because there is a lack of differential pressure between the pore and external atmosphere. 
         [0003]    To ensure that robust fluid manifolds are produced, such manifold are generally put through a series of acceptance tests. One acceptance test that is performed on the cast fluid manifold is a pressure test to determine whether the manifold is able to withstand internal pressures in use by preventing the pressurized test fluid such as, but not limited to, water that is located in the internal cavities of the manifold from communicating with the external environment. If the manifold is unable to withstand the internal pressures, then the manifold is either repaired or scrapped. One cause for a fluid manifold failing the pressure test would be if there is continuous or interconnected porosity between an inner surface and an outer surface of a wall of the manifold. In such instances, fluid may leak outwardly from the internal cavity of the component. 
         [0004]    Several aluminum alloys are designated as “A” by the Aluminum Association. One in particular has been gaining use in forming fluid manifolds. That alloy is designated A201, and is a Al—Cu alloy. 
         [0005]    At least one known method of repairing casting porosity is to remove an external surface area at the location of the interconnected porosity, and add new material via a weld. However, the interconnected porosity of the cast component makes it difficult to produce sound welds that effectively seal the manifold. In addition, some fluid manifolds, and in particular those formed of aluminum alloy A201 are extremely difficult to weld. 
         [0006]    Another known method for repairing casting porosity is to vacuum impregnate the fluid manifold with a low viscosity polymer, such as Loctite® Resinol® RTC, to seal the porosity. Also, Loctite® Resinol® 90C™ may be used, as may be other materials. However, such known method limits the maximum temperature through which the part may be used. For example, the maximum temperature may be below a glass transition temperature of the polymer. 
         [0007]    Cold spray has been utilized to deposit materials, such as aluminum alloys, to repair defects on parts that have sustained damage from use. However, known cold spray methods do not overcome the interconnected porosity problem mentioned above. 
       SUMMARY OF THE INVENTION AND ADVANTAGES 
       [0008]    A method of repairing a component having interconnected porosity applies a material to the area of the porosity through a cold deposition process. Components repaired by this method are also claimed. 
         [0009]    These and other features of the disclosed embodiments may be understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  shows an exemplary cast component having an example area of interconnected porosity. 
           [0011]      FIG. 1B  is a cross-sectional view schematically showing the interconnected porosity. 
           [0012]      FIG. 1C  is a micrograph of an area containing interconnected porosity in a cast component that leaked during a pressure test. 
           [0013]      FIG. 2A  shows a repaired component. 
           [0014]      FIG. 2B  shows a first step in a first embodiment of performing the repair. 
           [0015]      FIG. 2C  shows a subsequent step. 
           [0016]      FIG. 2D  shows yet another step. 
           [0017]      FIG. 3  shows a second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    An exemplary cast component such as fluid manifold  20  is illustrated in  FIG. 1A . Although the component is described as fluid manifold  20 , it should be appreciated that the component may be a fuel manifold, other fluid manifold, or other cast component. An area of interconnected porosity  22  is shown schematically on a body of the fluid manifold. As shown, fluid tubes  24  extend to different locations to distribute fluid, and a manifold member  28  serves to communicate fluid to the tubes  24 . As known, the interior of the manifold  20  must be able to withstand high pressures. However, as shown in  FIGS. 1B and 1C , interconnected porosity  22  challenges the ability of the manifold  20  to withstand internal pressures. As shown in  FIG. 1B , the porous areas extend from an outer face  23  entirely through to an inner face  25  of a wall. In such instances, fluid leaks between the two faces, and the manifold  20  would not be able to hold the fluid back from flowing from the inner face  25  to the outer face  23  as a result of internal pressures.  FIG. 1C  shows a micrograph of a sectioned manifold, such as manifold  20 , in an area that leaked during pressure test as a result of the interconnected porosity  22 . It should be appreciated that the component may be cast from aluminum alloy, titanium alloy, or steel. 
         [0019]      FIG. 2A  shows a repaired manifold  30 , having an area of repair  32  at the location of the interconnected porosity  22 . 
         [0020]    As shown in  FIG. 2B , an initial step is to remove material in an area  34  associated with an interconnected porosity  22  by mechanical or chemical means, such as grinding, machining, etching, or other applicable techniques. The depth of the blend can range from 0.25 mm to 2 mm with a length of the blend being on the order of at least 20 times the depth. The resultant surface may or may not be grit blasted with aluminum oxide or other acceptable media. The prepared surface is then cleaned by wiping and/or flushing with a solvent, such as isopropyl alcohol. Then, as shown in  FIG. 2C , a suitable material is deposited via cold spray deposition, such as shown in  36 , onto a cut away portion  34  by a cold spray nozzle  50 . Any other deposition processes may be used to provide sufficient energy to accelerate particles to a high enough velocity such that, upon impact, the metal particles deform and bond to the surface, building a relatively dense coating or structural deposit. The surface may be the prepared manifold surface or a previously deposited metal layer. The deposition process does not metallurgically transform the particles from their solid state. Various techniques to achieve this type of particle deposition have been evaluated and reduced to practice such as cold gas dynamic spraying (cold spray deposition), kinetic metallization, electromagnetic particle acceleration, modified high velocity air fuel spraying, or high velocity impact fusion (HVIF). These are examples of high velocity deposition processes where metallurgical transformation of powder metal particles is not encountered. Although the cold spray deposition process is disclosed, it should be appreciated that other cold deposition processes may be used. 
         [0021]    Suitable aluminum containing materials, with a composition of at least 50% aluminum, which may be deposited include, but are not limited to, pure aluminum, aluminum alloy A201, the base alloy, aluminum alloy 2014, aluminum alloy 2024, aluminum alloy 2219, aluminum alloy 6061. Again, these are Aluminum Association designations. The following type alloys can also be used: Al-12Si alloy, Al—Sc alloy, and aluminum alloy 6061/B4C, and others. 
         [0022]    In disclosed embodiments, a blending or grit blasting technique is used to form the area  34 . Any known machining process may be used to move to a substantially flush surface or face  38  as shown in  FIG. 2D  or the deposited material may be left as deposited. It should be appreciated that the flush surface  38  is substantially flush with respect to the outer face  23 . If the cold spray deposit is applied after the manifold&#39;s hot isostatic press, solution, and precipitation heat treatments, the cold spray deposit may be heat treated to relieve any residual stresses and to improve the deposits ductility at 35° C. to 260° C. for 1 hour to 24 hours. The heat treatment may be applied locally in the area of repair or globally to the entire manifold  20 . 
         [0023]    As shown in  FIG. 3 , in another embodiment, fluid manifold  42  may receive a cold spray coating at  44 , without any of the surface blending at the outer face. The surface may be grit blasted and cleaned with a suitable solvent prior to the cold spray process. The deposit may be finished machined to produce the desired surface finish on the raised cold spray deposit. The deposit may also be left unfinished. 
         [0024]    After the manifold  20  is repaired, it will be put through acceptance testing to facilitate ensuring a robust manifold and repair. If necessary, the manifold  20  may go through the repair process multiple times. 
         [0025]    In an exemplary method, a component is cast. The cast component is tested to identify any areas of interconnected porosity, which allow fluid communication between the interior cavities and the exterior environment. If such an area is identified, then the technique of  FIG. 2B-2D , or the technique of  FIG. 3  may be utilized. The cold spray deposition may be applied prior to or after a hot isostatic pressing treatment of the casting. 
         [0026]    Although embodiments have been disclosed, a worker of ordinary skill would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.