Abstract:
A holder for a component providing spray protection is provided. The insertion of a rod in the side face of the component, the side face is arranged within a housing of the holder, has the additional effect of providing spray protection. The rod rests on an inner face of the holder in one aspect.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of European Patent Office application No. 08019281.8 EP filed Nov. 4, 2008, which is incorporated by reference herein in its entirety. 
       FIELD OF INVENTION 
       [0002]    The invention relates to a holder for turbine blades or vanes with improved spray protection. 
       BACKGROUND OF INVENTION 
       [0003]    During thermal spraying, it is necessary to use structural features and process management to protect those regions which are not to be coated against so-called overspray. At present, surfaces which are not to be coated are protected by using devices which cover the regions to be protected by means of protective plates (so-called transition plates in the case of direct contact between the device and the component). In the case of large components, these protective plates are so long that the process-related increase in the temperature of the device leads to warping and therefore “folding away”. This movement exposes a gap between the component and the device, and sprayed material then penetrates into this gap and is deposited there. Furthermore, the protective plates are subject to wear, as a result of which this thermally-induced gap increases in size over time. Structural countermeasures on the protective plate have failed owing to the restrictions which the coating robot faces when trying to access the component. 
         [0004]    There is currently no satisfactory approach to a solution, and therefore the affected components, until now, have had to be remachined. 
       SUMMARY OF INVENTION 
       [0005]    The object of the invention is to solve the problem mentioned above. 
         [0006]    The object is achieved by a device as claimed in the claims. 
         [0007]    The dependent claims contain further advantageous measures which can be combined with one another as desired in order to achieve further advantages. 
         [0008]    An insertion plate (rod, bar, plate) has been designed since it is not possible to reinforce the previous design; this plate is inserted in the interlocking region, i.e. in the groove from the sealing plate of the blade or vane, and therefore efficiently protects that region of the blades or vanes which is not to be coated against overspray. Overspray which is deposited on the plate can be removed after the coating process with a simple tool, e.g. a screwdriver, three-square scraper etc. 
         [0009]    It is not necessary to carry out any complicated reworking at the previously affected points (removal of overspray), and the actual design of the device remains unchanged since the insertion plate is an additional measure. At this point, it should be emphasized that this solution makes it possible, for the first time, to successfully provide 100% protection against overspray even for those regions on which no reworking whatsoever is permitted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the figures: 
           [0011]      FIGS. 1 ,  2 ,  3  and  4  show different views of a device or parts of this device, 
           [0012]      FIG. 5  shows a gas turbine, and 
           [0013]      FIG. 6  shows a turbine blade or vane. 
           [0014]    The description and the figures illustrate only exemplary embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0015]      FIG. 1  shows a holder  4  for large components  7 ,  120 ,  130 . The invention is explained, only by way of example, with reference to turbine blades or vanes  120 ,  130 . A preferred holder  4  of this type is described in EP 1 808 269 A1. A turbine blade or vane  120 ,  130  or, in general terms, a component  7  is arranged in a holder  4  of this type. Certain regions of the component  7  should not be coated, and so these are simultaneously also covered by the holder  4 . In this case, by way of example, the side faces of the blade or vane platforms  403  of the turbine blade or vane  120 ,  130  should not be coated, but rather only the top side  22  of the blade or vane platform  403  and the main blade or vane part  406 . 
         [0016]    In the case of particularly large components, the gap  16  between the blade or vane platform  403  and the holder  4  becomes warped  4 ′ ( FIG. 2 ), and so the coating material penetrates into undesirable regions. In  FIG. 2 , this is indicated for one side of the holder  4  by the dashed line  4 ′. 
         [0017]    Therefore, a rod  13 , bar or plate is inserted, as part of the device  1 , into a recess  10  in the side face  19  of the blade or vane platform  403  ( FIG. 4 ). It may be necessary to redesign the turbine blade or vane  120 ,  130  so as to provide such a recess  10  or groove  10 . 
         [0018]    The rod  13  preferably projects beyond the recess  10 . At room temperature, the rod  13  likewise preferably comes very close to the inner side of the holder  4  (housing) or rests on it  4 . 
         [0019]    The rod  13  preferably extends in this recess  10  over the entire length of the recess (groove)  10  ( FIG. 3 ). This provides effective protection of the component  7 ,  120 ,  130  within the holder  4 . The recess  10  is preferably as long as possible. 
         [0020]      FIG. 2  shows a plan view of the holder  4 , the blade or vane platform  403  and the gap  16  between the holder  4  and the blade or vane platform  403 . 
         [0021]    The holder  4  preferably has a rectangular design. The rods  13  are preferably present only on the longest sides. They may also be present on all four sides. 
         [0022]    The rod  13  is preferably thicker than the wall of the housing  4  in the region  28  of the recess  10 . This ensures good mechanical stability. 
         [0023]      FIG. 5  shows, by way of example, a partial longitudinal section through a gas turbine  100 . 
         [0024]    In the interior, the gas turbine  100  has a rotor  103  with a shaft  101  which is mounted such that it can rotate about an axis of rotation  102  and is also referred to as the turbine rotor. 
         [0025]    An intake housing  104 , a compressor  105 , a, for example, toroidal combustion chamber  110 , in particular an annular combustion chamber, with a plurality of coaxially arranged burners  107 , a turbine  108  and the exhaust-gas housing  109  follow one another along the rotor  103 . 
         [0026]    The annular combustion chamber  110  is in communication with a, for example, annular hot-gas passage  111 , where, by way of example, four successive turbine stages  112  fowl the turbine  108 . 
         [0027]    Each turbine stage  112  is formed, for example, from two blade or vane rings. As seen in the direction of flow of a working medium  113 , in the hot-gas passage  111  a row of guide vanes  115  is followed by a row  125  formed from rotor blades  120 . 
         [0028]    The guide vanes  130  are secured to an inner housing  138  of a stator  143 , whereas the rotor blades  120  of a row  125  are fitted to the rotor  103  for example by means of a turbine disk  133 . 
         [0029]    A generator (not shown) is coupled to the rotor  103 . 
         [0030]    While the gas turbine  100  is operating, the compressor  105  sucks in air  135  through the intake housing  104  and compresses it. The compressed air provided at the turbine-side end of the compressor  105  is passed to the burners  107 , where it is mixed with a fuel. The mix is then burnt in the combustion chamber  110 , forming the working medium  113 . From there, the working medium  113  flows along the hot-gas passage  111  past the guide vanes  130  and the rotor blades  120 . The working medium  113  is expanded at the rotor blades  120 , transferring its momentum, so that the rotor blades  120  drive the rotor  103  and the latter in turn drives the generator coupled to it. 
         [0031]    While the gas turbine  100  is operating, the components which are exposed to the hot working medium  113  are subject to thermal stresses. The guide vanes  130  and rotor blades  120  of the first turbine stage  112 , as seen in the direction of flow of the working medium  113 , together with the heat shield elements which line the annular combustion chamber  110 , are subject to the highest thermal stresses. 
         [0032]    To withstand the temperatures which prevail there, they may be cooled by means of a coolant. 
         [0033]    Substrates of the components may likewise have a directional structure, i.e. they are in single-crystal form (SX structure) or have only longitudinally oriented grains (DS structure). 
         [0034]    By way of example, iron-base, nickel-base or cobalt-base superalloys are used as material for the components, in particular for the turbine blade or vane  120 ,  130  and components of the combustion chamber  110 . 
         [0035]    Superalloys of this type are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949. 
         [0036]    The blades or vanes  120 ,  130  may also have coatings which protect against corrosion (MCrAlX; M is at least one element selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and/or silicon, scandium (Sc) and/or at least one rare earth element or hafnium). Alloys of this type are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1. 
         [0037]    A thermal barrier coating, consisting for example of ZrO 2 , Y 2 O 3 -ZrO 2 , i.e. unstabilized, partially stabilized or fully stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide, may also be present on the MCrAlX. 
         [0038]    Columnar grains are produced in the thermal barrier coating by suitable coating processes, such as for example electron beam physical vapor deposition (EB-PVD). 
         [0039]    The guide vane  130  has a guide vane root (not shown here), which faces the inner housing  138  of the turbine  108 , and a guide vane head which is at the opposite end from the guide vane root. The guide vane head faces the rotor  103  and is fixed to a securing ring  140  of the stator  143 . 
         [0040]      FIG. 6  shows a perspective view of a rotor blade  120  or guide vane  130  of a turbomachine, which extends along a longitudinal axis  121 . 
         [0041]    The turbomachine may be a gas turbine of an aircraft or of a power plant for generating electricity, a steam turbine or a compressor. 
         [0042]    The blade or vane  120 ,  130  has, in succession along the longitudinal axis  121 , a securing region  400 , an adjoining blade or vane platform  403  and a main blade or vane part  406  and a blade or vane tip  415 . 
         [0043]    As a guide vane  130 , the vane  130  may have a further platform (not shown) at its vane tip  415 . 
         [0044]    A blade or vane root  183 , which is used to secure the rotor blades  120 ,  130  to a shaft or a disk (not shown), is formed in the securing region  400 . 
         [0045]    The blade or vane root  183  is designed, for example, in hammerhead form. Other configurations, such as a fir-tree or dovetail root, are possible. 
         [0046]    The blade or vane  120 ,  130  has a leading edge  409  and a trailing edge  412  for a medium which flows past the main blade or vane part  406 . 
         [0047]    In the case of conventional blades or vanes  120 ,  130 , by way of example solid metallic materials, in particular superalloys, are used in all regions  400 ,  403 ,  406  of the blade or vane  120 ,  130 . 
         [0048]    Superalloys of this type are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949. 
         [0049]    The blade or vane  120 ,  130  may in this case be produced by a casting process, by means of directional solidification, by a forging process, by a milling process or combinations thereof. 
         [0050]    Workpieces with a single-crystal structure or structures are used as components for machines which, in operation, are exposed to high mechanical, thermal and/or chemical stresses. 
         [0051]    Single-crystal workpieces of this type are produced, for example, by directional solidification from the melt. This involves casting processes in which the liquid metallic alloy solidifies to form the single-crystal structure, i.e. the single-crystal workpiece, or solidifies directionally. 
         [0052]    In this case, dendritic crystals are oriented along the direction of heat flow and form either a columnar crystalline grain structure (i.e. grains which run over the entire length of the workpiece and are referred to here, in accordance with the language customarily used, as directionally solidified) or a single-crystal structure, i.e. the entire workpiece consists of one single crystal. In these processes, a transition to globular (polycrystalline) solidification needs to be avoided, since non-directional growth inevitably forms transverse and longitudinal grain boundaries, which negate the favorable properties of the directionally solidified or single-crystal component. 
         [0053]    Where the text refers in general terms to directionally solidified microstructures, this is to be understood as meaning both single crystals, which do not have any grain boundaries or at most have small-angle grain boundaries, and columnar crystal structures, which do have grain boundaries running in the longitudinal direction but do not have any transverse grain boundaries. This second form of crystalline structures is also described as directionally solidified microstructures (directionally solidified structures). 
         [0054]    Processes of this type are known from U.S. Pat. No. 6,024,792 and EP 0 892 090 A1. 
         [0055]    The blades or vanes  120 ,  130  may likewise have coatings protecting against corrosion or oxidation e.g. (MCrAlX; M is at least one element selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and/or silicon and/or at least one rare earth element, or hafnium (Hf)). Alloys of this type are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1. 
         [0056]    The density is preferably 95% of the theoretical density. 
         [0057]    A protective aluminum oxide layer (TGO=thermally grown oxide layer) is formed on the MCrAlX layer (as an intermediate layer or as the outermost layer). 
         [0058]    The layer preferably has a composition Co-30Ni-28Cr-8A1-0.6Y-0.7Si or Co-28Ni-24Cr-10A1-0.6Y. In addition to these cobalt-base protective coatings, it is also preferable to use nickel-base protective layers, such as Ni-10Cr-12A1-0.6Y-3Re or Ni-12Co-21Cr-11Al-0.4Y-2Re or Ni-25Co-17Cr-10A1-0.4Y-1.5Re. 
         [0059]    It is also possible for a thermal barrier coating, which is preferably the outermost layer and consists for example of ZrO 2 , Y 2 O 3 -ZrO 2 , i.e. unstabilized, partially stabilized or fully stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide, to be present on the MCrAlX. 
         [0060]    The thermal barrier coating covers the entire MCrAlX layer. Columnar grains are produced in the thermal barrier coating by suitable coating processes, such as for example electron beam physical vapor deposition (EB-PVD). 
         [0061]    Other coating processes are possible, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal barrier coating may include grains that are porous or have micro-cracks or macro-cracks, in order to improve the resistance to thermal shocks. The thermal barrier coating is therefore preferably more porous than the MCrAlX layer. 
         [0062]    Refurbishment means that after they have been used, protective layers may have to be removed from components  120 ,  130  (e.g. by sand-blasting). Then, the corrosion and/or oxidation layers and products are removed. If appropriate, cracks in the component  120 ,  130  are also repaired. This is followed by recoating of the component  120 ,  130 , after which the component  120 ,  130  can be reused. 
         [0063]    The blade or vane  120 ,  130  may be hollow or solid in form. 
         [0064]    If the blade or vane  120 ,  130  is to be cooled, it is hollow and may also have film-cooling holes  418  (indicated by dashed lines).