Abstract:
Uber-cooled multi-alloy integrally bladed rotors (IBR) are made having blades with internal cooling passages with a cavity in the root portion attached to a disk having a protrusion on the periphery of the disk. The blades are put on the protrusion and the blade and disk are forced together, followed by locally heating the blade cavity/disk protrusion to a temperature between the blade and disk material softening temperatures, causing the protrusion to deform against the blade cavity, and holding them in place until bonding occurs. Subsequent to bonding the portion of the blade that defines the cavity is removed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is related to a commonly owned application filed of even date herewith having Ser. No. ______ with the title UBER-COOLED TURBINE AIRFOIL, the disclosure of which is incorporated herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    Cooled bladed rotors are commonly used in gas turbine engines to enable components to operate at higher gas path temperatures than would otherwise be possible with uncooled configurations. Longstanding practice in the turbine engine art for cooled bladed rotors is having separate parts (i.e., a disk and blades) joined together by mechanical means to produce a rotor assembly. The use of separate parts is driven by the need for different superalloys for the disk and the blade due to one set of mechanical properties needed for a disk location and a significantly different set of mechanical properties needed for a blade airfoil location. If taken to the next level of technology development, the disk itself would ideally be thermally-mechanically-processed (TMP) to have different mechanical properties within its bore, web, and rim. 
         [0003]    Present day integrally bladed rotors (IBR) are typically machined from a single forging having one chemistry. IBRs may also be produced by linear friction welding solid airfoils or hollow airfoils onto a disk (or hub if for the 1 st  stage of a gas turbine engine&#39;s fan). The blades and the disk may be of same chemistry or of different chemistries. For these examples of prior art IBR&#39;s, there is no internal cooling. The ability to produce a cooled integrally bladed rotor (IBR) which can operate thousands of hours in a thermal environment that exceeds the rotor&#39;s blade&#39;s superalloy&#39;s melting temperature by several hundred degrees Fahrenheit is not so simple. 
         [0004]    While advancements have been achieved with innovative attachment schemes (e.g., number of lugs, enhanced root profiles, curved root attachment configurations, etc.), demands for ever-increasing engine efficiency and reduced fuel consumption continue to challenge conventional blade and disk attachment design. It would be a significant advantage to have a method for producing an integrally bladed rotor (IBR) which joins two or more superalloys together, without the use of mechanical attachments, while offering super/hyper (i.e., uber) cooling within the IBR&#39;s blade locations such that the IBR can operate at higher than state-of-the-art gas path temperatures. 
       SUMMARY 
       [0005]    The present invention provides for metallurgically bonding a forged disk portion of the IBR (which may be made of one or more superalloys) to uber-cooled, additive manufactured, thermally mechanically processed superalloy blades. The end result is an Uber-cooled Multi-alloy IBR, which achieves the operating conditions currently needed in the industry. 
         [0006]    A disk is selected to have the uber-cooled blades attached and is machined to a configuration suitable for accepting an uber-cooled, additive manufactured blade or blade block of desired chemistry. The airfoil would be produced as taught in commonly owned patent application filed of even date herewith having the title Uber-Cooled Turbine Airfoil identified above. The airfoil would have its finished shape and could already contain a coating for oxidation protection if so desired. Metallurgical bonding is performed by applying pressure using conventional mechanical means and heat would be provided by resistance heating or induction heating, or other means. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of a rotor and a set of blades without a blade block prior to attachment. 
           [0008]      FIG. 2  is a perspective view of the rotor and set of blades of  FIG. 1  after attachment of the blades to the rotor. 
           [0009]      FIG. 3  illustrates the assembly of the disk and a blade containing a blade block prior to bonding to show the relationship therebetween. 
           [0010]      FIG. 4  shows the blade and disk of  FIG. 3  after bonding. 
           [0011]      FIG. 5  shows the bonded blade and disk after machining. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The superalloy turbine airfoils that are bonded to the disk in this invention have internal passages through which cooling air passes to provide super-cooling or uber-cooling of the airfoils. The internal passages are formed in configurations as desired. Such configurations include ellipsoidal, serpentine, layered, stacked, labyrinth and the like. The airfoils with passages are formed from a superalloy powder of the desired composition wherein the superalloy powder is sintered or melted by direct metal laser sintering (DMLS hereinafter), electron beam melting (EBM hereinafter), or other similar additive manufacturing processing. Layers of the superalloy powder are placed in a vacuum chamber (for EBM) or an argon chamber (for DMLS) and each layer is subjected to laser or electron beam heat that melts the powder into the shape of a two dimensional layer, followed by the next layer and the next until the part is formed. The internal passages not being fused continue to be filled with un-fused powder particles. 
         [0013]    Upon completion of the airfoil, it has to be vibrated and/or flushed with a fluid, such as, for example, a gas or a liquid to remove the powder particles that are in the internal passages. The part is then flow checked to verify the internal cavities are open and capable of meeting the internal flow conditions needed to meet the airfoil&#39;s design intent. A slurry with abrasive particles may be used to reduce internal surface roughness. The airfoil is then ready for bonding to the disk. 
         [0014]    For simplicity and clarification only, the FIGS show a few airfoils. In practice, a significantly greater number of airfoils would be bonded to a disk for a production part actually used in an engine. 
         [0015]      FIG. 1  illustrates rotor disk  20  with a plurality of protrusions  22  extending radially out from disk  20 . Positioned proximate each protrusion  22  is a blade  10  that is to be attached to its respective protrusion  22 .  FIG. 2  illustrates the same disk  20  with blades  10  attached thereto as is explained below. 
         [0016]      FIG. 3  is a cross-section showing a portion of the disk assembly and one of a plurality of blades to be joined to the disk. In  FIG. 3 , blade  10  has a recess  12  that is adapted to fit over protrusion  22 , which is an integral portion of disk  20 . Protrusion  22  and recess  12  are shaped to be closely conforming, in that the cross section of cavity  16  and protrusion  22  are closely matched. Bonding is desired on matching surfaces labeled  14  and  24  while portions of cavity  16  of blade  10  are present only for bonding and are subsequently removed. 
         [0017]    Faying surfaces  14  and  24  are to be clean and free of any dirt, oil, oxide or the like that could impede either the flow of electrical current or bonding and should be cleaned by conventional or known techniques. 
         [0018]    Bonding is accomplished using a combination of heat and pressure. Bonding is performed in a vacuum or inert atmosphere to eliminate oxidation, and vacuum does not have the possibility of inert gas entrapment in the bond. Force is applied normal to faying surfaces  14  and  24 , such as by application of hydraulic pressure means. Bonding forces on the order of 3-15 ksi (20.7-103.4 mpa) are appropriate although the exact bonding force is related to the specific materials used and the bonding temperature. 
         [0019]    Localized heating of faying surfaces  14  and  24  is obtained by passing a high current between blade  10  and disk  20 . Either AC or DC current sources are acceptable. 
         [0020]    The bonding temperature will depend on the specific alloys being bonded. A temperature range of 1700° F. to 2300° F. (927° C. to 1260° C.) are examples of temperatures used. The specific temperature selected is one at which the disk material softens but the blade material does not. A typical current flow to provide the necessary heating is about 3,600 to 4,000 amps for a time of about 0.5 to 4 hours. Induction heating is also within the scope of this invention. Use of a conventional furnace to heat the assembly to less than bonding temperature, followed by additional localized heating is also within the scope of this invention. 
         [0021]    Bonding between faying surfaces  14  and  24  as those surfaces merge is shown in  FIG. 4 .  FIG. 5  illustrates how side portions  16  are removed by conventional machining techniques after the bonding is complete since the cavity formed by element  16  is no longer needed. 
         [0022]    Producing an Uber-cooled Multi-alloy Integrally Bladed Rotor has several advantages over conventional mechanically attached bladed rotors. First, the elimination of leakage between a disk and blades provides improved engine efficiency. Also, disk broaching, disk super abrasive machining, and blade root grinding operations which are needed to create close tolerance mating attachment dovetail or firtree configurations (and which on occasion can generate undesirable surface conditions) are eliminated. Life limiting areas of localized high stress which are inherent in separate blade and disk mechanical attachment designs are eliminated. 
         [0023]    The bladed portion of the IBR includes a passageway in the side of the blade that feeds cooling air into the blade&#39;s internal passages. For a mechanically bladed rotor, a cover plate fits up against either side of the disk with the mechanically attached turbine blades in place. In the case of the internal passages formed in the diffusion bonded blade as it is attached to the disk, a passageway is machined after diffusion bonding that links the internal cavity of the turbine blade. A hole could already be in place prior to diffusion bonding. Machining the hole after diffusion bonding takes advantage of a more rigid airfoil root from the diffusion bonding process. 
         [0024]    Uber-cooling technology made possible by the use of additive manufacturing technology enables the bladed portion of the IBR to (a) operate at significantly higher gas path temperatures than previously possible, or (b) operate at state-of-the-art temperatures with less cooling air, or (c) operate at state-of-the-art temperatures using the same cooling air, but using a lower cost superalloy. Vibratory and/or resonance issues associated with mechanically attached bladed rotors are reduced. 
         [0025]    Fretting, galling, and other modes of wear normally associated with mechanically attached bladed rotors are eliminated. Overall rotor weight and overall module weight is reduced from that needed to accommodate a mechanically attached bladed rotor design and its containment. Uber-cooled multi-alloy integrally bladed rotors (IBR) can be tailored for use in both turbine applications and compressor applications. 
       DISCUSSION OF POSSIBLE EMBODIMENTS 
       [0026]    The following are nonexclusive descriptions of possible embodiments of the present invention. 
         [0027]    A method of making an integrally bladed rotor having blades with internal cooling passages attached to a disk by forming a cavity in a root portion of at least one blade having internal cooling, forming a protrusion on the periphery of the disk for each at least one blade having internal cooling passages and forcing the blade and disk together with localized heating and pressure to bond the blade to the disk and removing any part of the blade that is excess on the disk. 
         [0028]    The method of the preceding paragraph can optionally include additionally and/or alternatively, any one or more of the following features, configurations and/or additional components. 
         [0029]    Bonding may take place at a temperature range of 1700° F. to 2300° F. (927° C. to 1260° C.). 
         [0030]    Local heating may be provided by flowing current between the blade and the protrusion on the disk. 
         [0031]    The current flow to provide the heating can be about 3,600 to 4,000 amps for a time of about 0.5 to 4 hours. 
         [0032]    The bonding force can range from 3-15 ksi (20.7 -103.4 mpa). 
         [0033]    An integrally bladed rotor having blades with internal cooling passages where the blades have a cavity in the root portion, the disk has a protrusion for each blade, and the blade or blades is bonded to the disk protrusion. 
         [0034]    The integrally bladed rotor of the preceding paragraph can optionally include additionally and/or alternatively, any one or more of the following features, configurations and/or additional components. 
         [0035]    The blade can be bonded to the protrusion bonding at a temperature range of 1700° F. to 2300° F. (927° C. to 1260° C.). 
         [0036]    Local heating to bond the blade to the protrusion may be provided by flowing current between the blade and the protrusion. The current flow to provide the necessary heating may be about 3,600 to 4,000 amps for a time of about 0.5 to 4 hours. 
         [0037]    A bonding force may range from 3-15 ksi (20.7 -103.4 mpa). 
         [0038]    A method of making an integrally bladed rotor having blades with internal cooling passages and a cavity in the root portion attached to a disk having protrusions for each blade, by forcing the blade and the disk together at the protrusion, heating the blade/disk protrusion under heat and pressure until bonding occurs. 
         [0039]    The method of the preceding paragraph can optionally include additionally and/or alternatively, any one or more of the following features, configurations and/or additional components. 
         [0040]    Bonding may be performed at a temperature range of 1700° F. to 2300° F. (927° C. to 1260° C.). 
         [0041]    Bonding may use local heating provided by flowing current between the blade and the protrusion, wherein the current flow to provide the heating is about 3,600 to 4,000 amps for a time of about 0.5 to 4 hours. 
         [0042]    The bonding force may range from 3-15 ksi (20.7 -103.4 mpa). 
         [0043]    While the invention has been described with reference to an exemplary embodiment(s), 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(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.