Abstract:
According to a prior art, components having a crack are repaired, wherein the thus produced elongated recess is filled with a solder material which nevertheless produces a weak point. The inventive component, in addition to the material filled recess, comprises an additional material filled recess which extends transversely to the longitudinal direction of the cavity.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is the US National Stage of International Application No. PCT/EP2005/054722, filed Sep. 21, 2005 and claims the benefit thereof. The International Application claims the benefits of European application No. 04027671.9 filed Nov. 22, 2004, both of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION  
       [0002]     The invention relates to a component with a filled recess in accordance with the claims.  
       BACKGROUND OF THE INVENTION  
       [0003]     On occasions after production or often after prolonged use, components have cracks. These cracks are assessed, and depending on the assessment the component can be used or reused or may be separated out as unusable.  
         [0004]     If the crack length or defect size has exceeded a critical level, material is machined out around the crack and the recess which is formed is filled with a solder. However, in operational use, in particular because the solder has worse thermomechanical properties than the original material, a crack may form again at this location, leading to component failure, in particular in a relatively short time, since the crack can propagate more quickly through the weaker material than when the initial crack was formed.  
       SUMMARY OF INVENTION  
       [0005]     Therefore, it is an object of the invention to provide a component which overcomes this drawback.  
         [0006]     The object is achieved by the component as claimed in the claims. The subclaims list further advantageous configurations of the component, which can advantageously be combined with one another in any desired way.  
         [0007]     The idea of the invention consists, inter alia, in material being machined out, for example by milling, around the elongate crack not just in the direction in which the crack extends but also in a direction that is transverse with respect to the crack and in which the crack did not originally extend. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     In the drawing:  
         [0009]      FIG. 1  shows a component with a crack,  
         [0010]      FIG. 2  shows a repaired component according to the prior art,  
         [0011]     FIGS.  3  to  16  show exemplary embodiments of the component according to the invention,  
         [0012]      FIG. 17  shows a turbine blade or vane,  
         [0013]      FIG. 18  shows a combustion chamber,  
         [0014]      FIG. 19  shows a turbine. 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0015]      FIG. 1  shows a component  1 ,  1 ′ having a surface  5 , in or below which a crack  4  extends in a direction of extent  10 .  
         [0016]      FIG. 2  shows a component  1 ′ according to the prior art which has been repaired. Starting from the state shown in  FIG. 1 , material is machined out around the crack  4  on both sides along the extent of the crack, so as to form an elongate recess  7  which completely surrounds the original crack and is then filled with a material (for example solder) which for example differs from the material of the component  1 . Like the crack  4 , the recess  7  has an elongate shape (rectangular) in the direction of extent  10 .  
         [0017]     Alternatively, however, the recess  7  may have been formed as early as during production of the component, as is customary for example when casting components, in which a recess  7  is present in the component where a support was present in the casting mold, i.e. the recess  7  in the component need not necessarily be arranged at a location at which a crack was previously present.  
         [0018]     The component  1  comprises a first material, which is identical or of similar type to the second material in the recess  7  (for example in the case of welding) or is different than said second material (for example in the case of soldering).  
         [0019]     The second material, for example, by virtue of having a different microstructure, has worse thermomechanical properties than the component, which for example has a DS or SX structure. Different microstructures are produced when soldering or welding or welding using weld material of the same component as the base material.  
         [0020]     FIGS.  3  to  6  show exemplary embodiments of the component  1  according to the invention. The recess  7  extends not only in the direction of extent  10  but also in a transverse direction  11  that is transverse to the direction  10  and, unlike in  FIG. 2 , is not rectangular in contour, but rather L-shaped. The additional, transversely extending part of the recess  7 , the additional recess  13 , is in this case, by way of example, likewise rectangular in form.  
         [0021]     Both the original part of the recess  7  according to the prior art and the additional recess  13  may also be round rather than rectangular. For example, the original part of the recess  7  according to the prior art may have an elongate oval contour.  
         [0022]     The additional recess  13  may extend at an angle α of from &gt;0° to &lt;180° with respect to the direction of extent  10 . α is preferably ≧45°, ≧60°, ≧75° or 90°.  
         [0023]     The L shape may be present in any desired orientation in the component  1  ( FIGS. 3-6 ). The recess  7  is then for example filled with a solder or welded shut using a second material. This material generally differs from the material of the component  1  (superalloy, in particular based on nickel, cobalt or iron), but in any event has worse thermomechanical properties than the base material of the component  1 .  
         [0024]     Should a crack  4 ′ form for the first time or again in the filled recess  7 , this crack is diverted into the additional recess  13  ( FIGS. 3-6 ) and is thereby isolated from the stress present on the component  1 , with the result that the crack  4 ′ does not continue to grow. Consequently, the transversely running additional recess  13  has the function of a crack stopper which can divert the crack propagation into a direction to which the mechanical stresses which are present are not critical.  
         [0025]     In  FIGS. 7, 8 , the recess  7  is of T-shaped design. Should a crack  4 ′ again form in the recess  7  longitudinally with respect to direction  10 , it is diverted to the left and/or right in transverse direction  11 .  
         [0026]      FIG. 8  illustrates a further advantageous configuration of the invention.  
         [0027]     The T shape has a first T region T 1 , which extends in the transverse direction  11 , and a second T region T 2 , which extends in the opposite direction to the transverse direction  11 . The corresponding lengths l 1 , l 2  of the regions T 1 , T 2  may be equal.  
         [0028]     However, if, in operational use of the component  1 , different stresses σ 1 , σ 2  are present in the regions T 1 , T 2 , it is advantageous for the length l 2  to be correspondingly longer than the length l 1  if stress σ 2  is greater than σ 1 .  
         [0029]      FIG. 9  shows an H shape of the recess  7  as a further particularly advantageous form of the invention.  
         [0030]     In the transverse direction  11 , the H shape has a first and a second H region H 1  and H 2 , respectively, with corresponding lengths l 1 , l 2 .  
         [0031]     The lengths l 1 , l 2  may be identical. If, as seen in the direction of extent  10 , a greater stress σ 1  is present in region H 1  than the stress σ 2  in region H 2 , it is advantageous for the length l 1  to be corresponding longer than the length l 2  of region H 2 .  
         [0032]     Instead of angling off on a straight line, the additional recess  13  may also be curved in the form of an arc with respect to direction  10  and may taper to a point or be rounded at the end, as shown in  FIG. 10 .  
         [0033]     An additional recess  13  of this type may be designed in an L shape ( FIG. 10 ), a T shape or H shape ( FIG. 11 ).  
         [0034]     It is also possible for the contour of the H shape to be rounded in the corner regions, so as to adopt the shape of a bone ( FIG. 12 ).  
         [0035]      FIG. 13  shows a further exemplary embodiment of the component  1  according to the invention.  
         [0036]     In this example, the recess  7  (illustrated here by way of example in the shape of an H) has been filled with an insert  16  and a solder  19 . The insert  16  has in particular the contour of the recess  7  and consists for example of the same material as the component  1  and is held in place by the solder  19  in the recess  7  or is welded to the component  1 .  
         [0037]     The recess  7  is in particular formed in such a way that it encompasses the entire crack  4 , even if said crack  4  does not always run in a straight line in the direction of extent  10  ( FIG. 14 ). According to the prior art, this can give rise to a very wide recess  8  (as indicated by dashed lines in  FIG. 15 ) if the crack  4  propagates not only in a direction of extent  10  but also transversely to the direction of extent  10 . According to the invention, the recess  7  with the additional recess  13  is once again for example of L-shaped design, with the L shape rotated with respect to the crack  4  in such a way that much less material has to be removed compared to the recess  8  of the prior art ( FIG. 15 ).  
         [0038]     The component  1  may of course have a plurality of cracks  4  at vulnerable locations, with these cracks extending in different directions of extent  10 ,  10 ′ ( FIG. 16 ). In this event, a recess  7 ,  7 ′ according to the invention with the additional recess  13 ,  13 ′ is formed at each crack.  
         [0039]     However, it is also possible for a crack  4  to have forked, for example, as illustrated in  FIG. 16 . In this case, for example with the crack profile illustrated in  FIG. 16 , it is once again possible to match an L shape to the crack, or alternatively two L shapes are used, matched to the two different branches of the crack, in which case the two recesses  7 ,  7 ′ for example also touch or partly overlap one another.  
         [0040]     The component  1  may be a turbine blade or vane  120 ,  130  of a turbine, for example of a steam turbine or a gas turbine  100  for a power plant, or of an aircraft, or a heat shield element  155 .  
         [0041]      FIG. 17  shows a perspective view of a blade or vane  120 ,  130 , which extends along a longitudinal axis  121 .  
         [0042]     The blade or vane  120  may be a rotor blade  120  or a guide vane  130  of a turbomachine. The turbomachine may be a gas turbine of an aircraft or of a power plant for generating electricity, a steam turbine or a compressor.  
         [0043]     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 . As a guide vane  130 , the vane  130  may have a further platform (not shown) at its vane tip  415 . 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 . 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. 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 .  
         [0044]     In the case of conventional blades or vanes  120 ,  130 , by way of example solid metallic materials are used in all regions  400 ,  403 ,  406  of the blade or vane  120 ,  130 . The blade or vane  120 ,  130  may in this case be produced by a casting process, also by means of directional solidification, by a forging process, by a milling process or combinations thereof.  
         [0045]     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. 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.  
         [0046]     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.  
         [0047]     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).  
         [0048]     Processes of this type are known from U.S. Pat. No. 6,024,792 and EP 0 892 090 A1.  
         [0049]     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, as described in  FIGS. 3-13 . This is followed by recoating of the component  120 ,  130 , after which the component  120 ,  130  can be reused.  
         [0050]     The blade or vane  120 ,  130  may be hollow or solid in form. If the blade or vane  120 ,  130  is to be cooled, it is hollow and may also have film-cooling holes (not shown). To protect against corrosion, the blade or vane  120 ,  130  has, for example, generally metallic coatings, and to protect against heat it generally also has a ceramic coating.  
         [0051]      FIG. 18  shows a combustion chamber  110  of a gas turbine  100 . The combustion chamber  110  is configured, for example, as what is known as an annular combustion chamber, in which a multiplicity of burners  102  arranged circumferentially around the turbine shaft  103  open out into a common combustion chamber space. For this purpose, the combustion chamber  110  overall is of annular configuration positioned around the turbine shaft  103 .  
         [0052]     To achieve a relatively high efficiency, the combustion chamber  110  is designed for a relatively high temperature of the working medium M of approximately 1000° C. to 1600° C. To allow a relatively long service life even with these operating parameters, which are unfavorable for the materials, the combustion chamber wall  153  is provided, on its side which faces the working medium M, with an inner lining formed from heat shield elements  155  (as a further example of a component  1 ). On the working medium side, each heat shield element  155  is equipped with a particularly heat-resistant protective layer or is made from a material that is able to withstand high temperatures. On account of the high temperatures in the interior of the combustion chamber  110 , a cooling system is also provided for the heat shield elements  155  and/or for their holding elements.  
         [0053]     The materials of the combustion chamber wall and their coatings may be similar to those of the turbine blades or vanes.  
         [0054]     The combustion chamber  110  is designed in particular to detect losses of the heat shield elements  155 . For this purpose, a number of temperature sensors  158  are positioned between the combustion chamber wall  153  and the heat shield elements  155 .  
         [0055]      FIG. 19  shows, by way of example, a partial longitudinal section through a gas turbine  100 . In the interior, the gas turbine  100  has a rotor  103  which is mounted such that it can rotate about an axis of rotation  102  and is also referred to as the turbine rotor.  
         [0056]     An intake housing  104 , a compressor  105 , a, for example, toroidal combustion chamber  110 , in particular an annular combustion chamber  106 , with a plurality of coaxially arranged burners  107 , a turbine  108  and the exhaust-gas housing  109  follow one another along the rotor  103 .  
         [0057]     The annular combustion chamber  106  is in communication with a, for example, annular hot-gas passage  111 , where, by way of example, four successive turbine stages  112  form the turbine  108 . 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 .  
         [0058]     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 . A generator (not shown) is coupled to the rotor  103 .  
         [0059]     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.  
         [0060]     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 bricks which line the annular combustion chamber  106 , are subject to the highest thermal stresses.  
         [0061]     To be able to withstand the temperatures which prevail there, they may be cooled by means of a coolant. 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).  
         [0062]     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 . Superalloys of this type are known, for example, from EP 1204776, EP 1306454, EP 1319729, WO 99/67435 or WO 00/44949; these documents form part of the disclosure.  
         [0063]     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 represents yttrium (Y) and/or silicon and/or at least one rare earth element) and heat by means of a thermal barrier coating.  
         [0064]     The thermal barrier coating consists, for example, of ZrO 2 , Y 2 O 4 -ZrO 2 , i.e. unstabilized, partially stabilized or fully stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide. Columnar grains are produced in the thermal barrier coating by suitable coating processes, such as for example electron beam physical vapor deposition (EB-PVD).  
         [0065]     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 .