Patent Publication Number: US-2007107217-A1

Title: Method for surface blasting of integrally bladed rotors

Description:
This application claims the priority of German Patent Document No. 10 2005 024 733.4, filed May 31, 2005, the disclosure of which is expressly incorporated by reference herein.  
     BACKGROUND AND SUMMARY OF THE INVENTION  
      The invention relates to a method for surface blasting integrally bladed rotors, in particular integrally bladed gas turbine rotors.  
      Gas turbines, especially aircraft engines, have at least one rotor equipped with rotating blades, especially in the area of the compressor and/or turbine; there is a growing trend for these blades to be designed as an integral part of the rotor. Integrally bladed rotors are referred to as either blisk (bladed disk) or bling (bladed ring), depending on whether the rotor base body is disk-shaped or ring-shaped. During operation of a gas turbine, the rotors are under very high loads. To reduce the wear rate, integrally bladed rotors are strengthened by special surface processing techniques.  
      Shot peening or blasting with steel balls, i.e., shot, is used for surface bonding of integrally bladed rotors in the related art. In this method according to the related art, blasting balls, which may be in the form of steel balls or even ceramic balls, are accelerated with the help of compressed air or directed through at least one nozzle at the surface sections of the integrally bladed rotor that are to be strengthened. With such nozzles, only a narrowly limited section, i.e., surface area of the integrally bladed rotor, can be strengthened, so the nozzle or each nozzle directing the peening balls used for surface strengthening at the integrally bladed rotor must move or be moved in relation to the integrally bladed rotor. According to the related art, surface areas of the blades of the integrally bladed rotor and surface areas of the hub and/or annular clearance between neighboring blades are blasted one after the other with different nozzle settings. It follows directly from this that the method used for surface blasting of integrally bladed rotors according to the related art takes a very long time and is also associated with high equipment costs.  
      Against this background, the problem on which the present invention is based is to create a novel method for surface blasting of integrally bladed rotors.  
      According to this invention, in an embodiment, the method for surface blasting of integrally bladed rotors includes at least the following steps: a) providing an integrally bladed rotor; b) providing a vibratory grinding system; c) arranging the integrally bladed rotor in a grinding container of the vibratory grinding system; d) then filling the grinding container of the vibratory grinding system with blasting balls; e) operating the vibratory grinding system filled with the blasting balls and the integrally bladed rotor to accelerate the blasting balls, so that the accelerated blasting balls strengthen the integrally bladed rotor simultaneously on the surfaces of all rotor blades and in the annular clearance between neighboring rotor blades.  
      In the sense of the present invention, it is provided that a vibratory grinding system that is generally used for abrasive vibratory grinding and/or chemically supported vibratory grinding should be used for surface blasting of integrally bladed rotors. To do so, the integrally bladed rotor whose surface is to be strengthened is positioned in the grinding container of the vibratory grinding system, while the grinding container is still filled with steel balls. By operating the vibratory grinding system filled with the integrally bladed rotor and the steel balls, the integrally bladed rotor is simultaneously strengthened on the surfaces of all the rotor blades and on the surface of the hub and/or in the area of the annular clearance between the neighboring rotor blades. This makes it possible to significantly shorten the process time needed for surface blasting of integrally bladed rotors. The vibratory grinding system that is needed anyway for vibratory grinding is sent for another use in the sense of the present invention, namely surface strengthening and/or surface blasting, thereby making it possible to reduce equipment costs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred embodiments of the present invention are derived from the following description. An exemplary embodiment of this invention is explained in greater detail with reference to the drawings without being limited thereto. The figures show:  
       FIG. 1  is an arrangement consisting of a vibratory grinding system and an integrally bladed rotor to be strengthened in the area of its surface, shown in cross-section to illustrate the inventive method; and  
       FIG. 2  is the area of detail II of the arrangement according to  FIG. 1  as seen from above. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      The present invention is described in greater detail below with reference to  FIGS. 1 and 2 .  
       FIG. 1  shows a schematic diagram of a vibratory grinding system  10  comprising a grinding container  11  and a motor  12  permanently connected to the grinding container  11 . The motor  12  is driven in operation of the vibratory grinding system  10  and in doing so, it rotates an unbalanced body  14  in the direction of the arrow  13 . The rotation of the unbalanced body  14  induces a tumbling motion of the grinding container  11 .  
      In the sense of the present invention, for surface blasting of an integrally bladed rotor  15 , it is positioned in the grinding container  11  of the vibratory grinding system  10 . In addition, the grinding container  11  of the vibratory grinding system  10  is filled with blasting balls  16 ; the balls may be designed as ceramic balls or steel balls. As  FIGS. 1 and 2  indicate, the blasting balls  16  are placed in the grinding container  11  in such a way that the integrally bladed rotor  15  is surrounded by the blasting balls  16  on all sides in the area of its rotor blades  17  and in the area of its hub and/or the annular clearance  18  between neighboring rotor blades  17 .  
      In operation of the vibratory grinding system  10  filled with the blasting balls  16  and the integrally bladed rotor  15 , the grinding container  11  and the integrally bladed rotor  15  execute a tumbling motion, so the blasting balls  16  are accelerated in relation to the grinding container  11 , as well as the integrally bladed rotor  15 , and they travel on helical paths through the grinding container  11 . In this process, the blasting balls  16  strike the surfaces of the integrally bladed rotor  15  and, in doing so, deliver their energy to same. The integrally bladed rotor  15  is surface-blasted and/or surface-strengthened at the same time in this way in the area of all the rotor blades  17  and in the area of the hub and/or the annular clearance  18  between neighboring rotor blades  17 .  
      The integrally bladed rotor  15  is preferably arranged in the grinding container  11  of the vibratory grinding system  10  in such a way that the integrally bladed rotor  15  is rigidly connected to the grinding container  11 , i.e., there is no degree of freedom for any relative movement between the integrally bladed rotor  15  and the grinding container  11 . Then the grinding container  11  and the integrally bladed rotor  15  execute an identical tumbling motion in operation of the vibratory grinding system  10  for surface blasting of the rotor  15 .  
      As an alternative, it is also possible to arrange the integrally bladed rotor  15  in the grinding container  11  of the vibratory grinding system  10  in such a way that the integrally bladed rotor  15  is connected to the grinding container  11  of the vibratory grinding system  10  while retaining one degree of freedom for a relative movement between the rotor  15  and the grinding container  11 . With regard to the grinding container  11 , the integrally bladed rotor  15  can then move about an axis of rotation in relation to the grinding container  11  but, in the axial direction, it is rigidly connected to the grinding container  11 .  
      Thus, with the inventive method, an integrally bladed gas turbine rotor  15  is strengthened, e.g., by hardening, solidifying, or consolidating, simultaneously in the area of all the rotor blades  17  and the hub and/or the annular space  18  between neighboring rotor blades  17 , i.e., on all aerodynamically and/or hydrodynamically relevant surface areas of the integrally bladed rotor. According to  FIG. 1 , surfaces of the integrally bladed rotor  15  that are not to be strengthened, e.g., surface areas on the inside radially of rotor disks  19  and surface areas on gasket carriers  20 , are covered with the help of cover devices  21  to prevent the blasting balls  16  from striking these surface areas. As an alternative, however, it is also possible to simultaneously blast one or more of the surface areas covered by the cover devices  21  in  FIG. 1  at the same time with the other surface areas.  
     List of Reference Numerals  
     
         
           10  vibratory grinding system  
           11  grinding container  
           12  motor  
           13  direction of movement  
           14  unbalanced body  
           15  integrally bladed rotor  
           16  blasting balls  
           17  rotor blade  
           18  annular space  
           19  rotor disk  
           20  gasket carrier  
           21  cover device  
       
    
      The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof