Abstract:
It is often not possible to use a rectilinear beam guidance for laser processing in the case of curved components, since the laser and the associated optics are often excessively large. Consequently, according to the invention, a focusing apparatus with beam deflection is proposed that reduces the relevant beam region by means of appropriate lenses and mirror such that it is possible to feed to relatively small locations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefits of European application No. 07023065.1 filed Nov. 28, 2007 and is incorporated by reference herein in its entirety. 
       FIELD OF INVENTION 
       [0002]    The invention relates to a focusing apparatus for electromagnetic waves. 
       BACKGROUND OF THE INVENTION 
       [0003]    Electromagnetic waves such as laser beams are often used in order to process metal, ceramic components or layer systems. 
         [0004]    In this case, the laser beam is guided in various ways onto the surface of the component to be processed. Difficulties in guiding the laser beam onto the relevant location at a specific angle can occur for processing locations that are difficult to access, such as excessively strongly curved surfaces, for example, because of the size of the laser apparatus. 
       SUMMARY OF INVENTION 
       [0005]    It is therefore an object of the invention to indicate a focusing apparatus for electromagnetic waves with the aid of which the above-mentioned problem is solved. 
         [0006]    The object is achieved by a focusing apparatus having beam deflection as claimed in the claims. 
         [0007]    The subclaims list further advantageous measures that can, in turn, be combined at will with one another in order to attain further advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    In the drawings: 
           [0009]      FIG. 1  shows a lens arrangement according to the prior art, 
           [0010]      FIG. 2  shows a schematic of the inventive arrangement, 
           [0011]      FIG. 3  shows a schematic of the division of the focal length, 
           [0012]      FIG. 4  shows an exemplary embodiment of the inventive focusing apparatus with beam deflection, 
           [0013]      FIG. 5  shows a gas turbine, 
           [0014]      FIG. 6  shows a turbine blade in perspective, and 
           [0015]      FIG. 7  shows a list of superalloys. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0016]      FIG. 1  illustrates an arrangement of lenses  40 ,  43  and mirror  13  from the prior art. 
         [0017]    The laser beams  29  or, in general electromagnetic beams  29  strike a collimator lens  40  and, subsequently, a mirror  13 , the result being that the laser beams  29  are deflected onto a focusing lens  43  that has a focal length f and in the case of which a focal point lies at a processing location  34  on a substrate  22 . 
         [0018]    The inventive design for a focusing apparatus  1  is illustrated schematically in  FIG. 2 . 
         [0019]    The principle can be applied to all types of electromagnetic radiation such as, for example, laser beams, X-radiation or else electron beams. 
         [0020]    The focusing device  1  is explained with the aid of laser beams  29  merely by way of example. 
         [0021]    The laser beams  29  strike the collimator lens  40  and thereafter the focusing lens  43 , a mirror  13  being arranged downstream of the focusing lens  43 , that is to say preferably in the beam path between focusing lens  43  and substrate  22 , and directs the laser beams  29  onto the processing location  34  of the substrate  22 . 
         [0022]    The mirror  13  is used for a deflecting device  13  merely by way of example. 
         [0023]    A preferred division of the focal length f of the focusing lens  43  is illustrated schematically in  FIG. 3 . 
         [0024]    The focal length f is divided into the distance of the focusing lens  43  from the mirror  13 , and from the mirror  13  to the surface of the component  22 . 
         [0025]    The numerical values ¾ and ¼ are merely exemplary. 
         [0026]      FIG. 4  shows a further focusing apparatus  1  with beam deflection for electromagnetic beams  29 . 
         [0027]    The component  22  to be processed here constitutes by way of example a turbine blade  120 ,  130  ( FIGS. 5 ,  6 ) which has a surface  37  curved in such a way that the processing location  34  is not accessible to conventional processing optics. 
         [0028]    The focusing apparatus  1  can, however, also process flat surfaces. 
         [0029]    The substrate  22  preferably has a superalloy in accordance with  FIG. 7 . 
         [0030]    It is preferably a layer system composed of a substrate having metal and/or ceramic layers on the substrate  22 . 
         [0031]    The focusing apparatus  1  preferably has a housing, preferably a first housing  4  and a second housing  7 . 
         [0032]    The housings  4 ,  7  are preferably funnel-shaped, in particular of conical design. The invention is explained below with the aid of the funnels  4 ,  7  merely by way of example. 
         [0033]    The first funnel  4  extends along a first longitudinal direction  16 . 
         [0034]    The ratio of the lengths of the funnels  4 ,  7  is immaterial, since in accordance with  FIG. 3  the focal length f can be divided at will between a fraction between the focusing lens  43  and the mirror  13 , and the remaining fraction between the mirror  13  and the component surface (processing location  34 ). 
         [0035]    The second funnel  7  is preferably of smaller, that is to say shorter, design, and preferably of smaller design in the maximum cross section than the first funnel  4 . The first and second funnels  7  border one another. A second longitudinal axis  19  of the second funnel  7  extends at an angle α to the first longitudinal axis  29  other than 180°. α is preferably between &lt;180° and 90°. 
         [0036]    Mirrors for a beam deflection of 90° are usual in the market. 
         [0037]    In the region of an inlet opening of a housing, in particular in a first inlet opening  25  of the first funnel  4 , there is preferably present the focusing lens  43 , which focuses the incoming laser beams  29  onto a processing location  34  of the component. These laser beams  29  are directed onto a deflecting device  13  for electromagnetic beams, in particular onto a mirror  13 . 
         [0038]    The deflecting device  13  is located in the housing  4 ,  7 , preferably partly in the first funnel  4  and for the other part in the second funnel  7 , which adjoins a first outlet opening  28  of the first funnel  4 . 
         [0039]    The outlet opening  28  of the first funnel  4  corresponds in cross section to the cross section of the second inlet opening of the second funnel  7 . 
         [0040]    The focusing lens  43  directs the laser beams  29  onto the mirror  13 , from which the laser beams  29  are directed into the region of a second outlet opening  31  of the second funnel  7 . 
         [0041]    As shown in  FIG. 3 , it is thereby possible to process a processing location  34  in the region of the curved surface  37  of the component  22 . If the longitudinal axis  19  of the second funnel  7  is lengthened, that is to say a central ray of the laser beam  29  that processes the component  22 ,  120 ,  130 , it would be seen that a trailing edge of the curved component  22  would be cut, and so it would be impossible to process using a rectilinearly guided laser beam. 
         [0042]    The second funnel  7  has an outlet opening  31  from which the laser beams  29  emerge and strike the component  22 . 
         [0043]    Furthermore, the focusing device  1  can have a number of funnels and, if appropriate, correspondingly a number of deflecting devices in order to deflect the laser beams  29  in stepwise fashion. The funnels  4 ,  7  can be movable relative to one another. In this case, the position of the mirror  13  is preferably also adjusted correspondingly. 
         [0044]    The focusing apparatus optionally has a gas feed  37  into the housing, preferably into the funnel  4  or into the funnel  7  downstream of the focusing lens  43 , in order to introduce into the funnel  4  or funnel  7  a process gas that strikes the component  22  from a second outlet opening  31  of the second funnel  7 , doing so together with the laser beam  29 . Air, argon, oxygen or nitrogen, in particular, can be used as process gas. 
         [0045]      FIG. 5  shows by way of example a gas turbine  100  in a longitudinal partial section. 
         [0046]    In the interior, the gas turbine  100  has a rotor  103  that is rotatably mounted about a rotation axis  102  and has a shaft  101 , which is also denoted as a turbine rotor. 
         [0047]    Following successively along the rotor  103  are a suction housing  104 , a compressor  105 , a, for example, toruslike combustion chamber  110 , in particular ring combustion chamber, with a number of coaxially arranged burners  107 , a turbine  108  and the exhaust gas housing  109 . 
         [0048]    The ring combustion chamber  110  communicates with a, for example, annular hot gas duct  111 . Four turbine stages  112  connected one behind another, for example, form the turbine  108  there. 
         [0049]    Each turbine stage  112  is formed, for example, from two blade rings. Seen in the flow direction of a working medium  113 , a row  125  formed from rotor blades  120  follows in the hot gas duct  111  of a guide blade row  115 . 
         [0050]    The guide blades  130  are fastened in this case on an inner housing  138  of a stator  143 , whereas the guide blades  120  of a row  125  are fitted by means of a turbine disk  133  on the rotor  103 , by way of example. 
         [0051]    A generator or a working machine (not illustrated) is coupled to the rotor  103 . 
         [0052]    During the operation of the gas turbine  100 , air  135  is sucked in by the compressor  105  through the suction housing  104  and compressed. The compressed air provided at the turbine-side end of the compressor  105  is guided to the burners  107  and mixed there with a fuel. The mixture is then burned in the combustion chamber  110  while forming the working medium  113 . From there, the working medium  113  flows along the hot gas duct  111  past the guide blades  130  and the rotor blades  120 . The working medium  113  expands at the rotor blades  120  in an impulse-transmitting fashion such that the rotor blades  120  drive the rotor  103  and the latter drives the working machine coupled to it. 
         [0053]    The components exposed to the hot working medium  113  are subjected to thermal loads during operation of the gas turbine  100 . The guide blades  130  and rotor blades  120  of the first turbine stage  112  as seen in the flow direction of the working medium  113 , in addition to the heat shield elements lining the ring combustion chamber  110 , are subjected to the greatest thermal loading. 
         [0054]    In order to withstand the temperatures prevailing there, said guide blades  130  and rotor blades  120  can be cooled by means of a coolant. 
         [0055]    Substrates of the components can likewise have a directional structure, that is to say they are monocrystalline (SX structure), or have only longitudinally directed grains (DS structure). 
         [0056]    Iron-, nickel- or cobalt-based superalloys, for example, are used as material for the components, in particular for the turbine blades  120 ,  130  and components of the combustion chamber  110 . 
         [0057]    Such superalloys 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. 
         [0058]    The blades  120 ,  130  can likewise have coatings against corrosion (MCrAlX; M is at least one element of the group comprising iron (Fe), cobalt (Co), nickel (Ni), while X is an active element and stands for yttrium (Y) and/or silicon, scandium (Sc) and/or at least one element of the rare earths, or hafnium). Such alloys are known from EP 0 486 489 B1, EP 0 786 017B1, EP 0 412 397 B1 or EP 1 306 454 A1. 
         [0059]    Furthermore, there can be present on the MCrAlX a thermal insulating layer consisting, for example, of ZrO 2 , Y 2 O 3 —ZrO 2 , that is to say it is unstabilized, partially stabilized or completely stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide. Columnar grains are produced in the thermal insulation layer by means of suitable coating methods such as, for example, electron beam physical vapor deposition (EB-PVD). 
         [0060]    The guide blade  130  has a guide blade foot (not represented here) facing the inner housing  138  of the turbine  108 , and a guide blade head opposite the guide blade foot. The guide blade head faces the rotor  103  and is fastened on a fastening ring  140  of the stator  143 . 
         [0061]      FIG. 6  shows a perspective view of a rotor blade  120  or guide blade  130  of a turbomachine that extends along a longitudinal axis  121 . 
         [0062]    The turbomachine can be a gas turbine of an aircraft or of a power plant for electricity generation, a steam turbine or a compressor. 
         [0063]    Along the longitudinal axis  121 , the blades  120 ,  130  successively have a fastening region  400 , a blade platform  403  bordering thereon, as well as a blade leaf  406  and a blade tip  415 . 
         [0064]    The blade  130  can have a further platform (not illustrated) on its blade tip  415  as guide blade  130 . 
         [0065]    Formed in the fastening region  400  is a blade foot  183  that serves to fasten the rotor blades  120 ,  130  on a shaft or a disk (not illustrated). 
         [0066]    The blade foot  183  is, for example, configured as a hammerhead. Other configurations as fir-tree or swallowtail foot are also possible. 
         [0067]    The blades  120 ,  130  have a leading edge  409  and a trailing edge  412  for a medium that flows past the blade leaf  406 . 
         [0068]    In the case of conventional blades  120 ,  130 , solid metallic materials, in particular superalloys, are used in all regions  400 ,  403 ,  406  of the blades  120 ,  130 . 
         [0069]    Such superalloys 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. 
         [0070]    The blades  120 ,  130  can be produced in this case by a casting method, also by means of directional solidification, by a forging method, by a milling method, or by combinations thereof. 
         [0071]    Workpieces having a monocrystalline structure or structures are used as components for machines that are exposed in operation to high mechanical, thermal and/or chemical loadings. 
         [0072]    Production of such monocrystalline workpieces is performed, for example, by directional solidification from the melt. What are involved here are casting methods in which the liquid metal alloy solidifies to form the monocrystalline structure, that is to say the monocrystalline workpiece, or directionally. In this process, dendritic crystals are aligned along the thermal flow, and form either a columnar crystalline grain structure (columnar, that is to say grains that extend over the entire length of the workpiece and are described here as directionally solidified in accordance with general linguistic usage) or a monocrystalline structure, that is to say the entire workpiece consists of a single crystal. It is necessary in these methods to avoid the transition to the globulitic (polycrystalline) solidification, since transverse and longitudinal grain boundaries necessarily form owing to non-directional growth and nullify the good properties of the directionally solidified or monocrystalline component. 
         [0073]    Looking in general at directionally solidified structures, what is meant is both monocrystals, which do not have grain boundaries, or have at most small angle grain boundaries, and columnar crystalline structures that, while having grain boundaries extending in a longitudinal direction, do not have any transverse grain boundaries. In the case of these second named crystalline structures, one also speaks of directionally solidified structures. 
         [0074]    Such methods are known from U.S. Pat. No. 6,024,792 and EP 0 892 090 A1. 
         [0075]    The blades  120 ,  130  can likewise have coatings against corrosion or oxidation, for example (MCrAlX; M is at least one element of the group comprising iron (Fe), cobalt (Co) and nickel (Ni), while X is an active element and stands for yttrium (Y) and/or silicon and/or at least one element of the rare earth, or hafnium (Hf)). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1, which are to be part of this disclosure with reference to the chemical composition of the alloy. The density preferably amounts to 95% of the theoretical density. 
         [0076]    A protective aluminum oxide layer (TGO=thermal grown oxide layer) is formed on the MCrAlX layer (as intermediate layer or as outermost layer). 
         [0077]    The layer composition preferably exhibits Co-30Ni-28Cr-8Al-0, 6Y-0, 7Si or Co-28Ni-24Cr-10Al-0, 6Y. In addition to these cobalt-based protective coatings, use is also preferably made of nickel-based protective layers such as Ni-10Cr-12Al-0, 6Y-3Re or Ni-12Co-21Cr-11Al-0, 4Y-2Re or Ni-25Co-17Cr-10Al-0, 4Y-1, 5Re. 
         [0078]    Furthermore, there can be present on the MCrAlX a thermal insulation layer which is preferably the outermost layer and consists, for example, of ZrO 2 , Y 2 O 3 —ZrO 2 , that is to say it is unstabilized, partially stabilized or completely stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide. 
         [0079]    The thermal insulation layer covers the entire MCrAlX layer. 
         [0080]    Columnar grains are produced in the thermal insulation layer by means of suitable coating methods such as, for example electron beam physical vapor deposition (EB-PVD). 
         [0081]    Other coating methods are conceivable, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal insulation layer can have grains that are porous and affected by microcracks or macrocracks for the purpose of improved thermal shock resistance. The thermal insulation layer is thus preferably more porous than the MCrAIX layer. 
         [0082]    Reprocessing (refurbishment) means that components  120 ,  130  must, if appropriate, be freed from protective layers after being used (for example by sandblasting). This is followed by removing the corrosion and/or oxidation layers or products. If appropriate, cracks in the component  120 ,  130  are also repaired. Thereafter, the component  120 ,  130  is recoated, and the component  120  or  130  is reused. 
         [0083]    The blades  120 ,  130  can be of hollow or solid design. When the blade  120 ,  130  is to be cooled, it is hollow and, if appropriate, also has film-cooling holes  418  (indicated by dashed lines).