Abstract:
Disclosed is an apparatus and process for coating a component with aligning device. Alignments or checking of the spray cone take place within the coating apparatus via an optically transparent reference plate which is optically evaluated.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefits of European application No. 07006095.9 filed Mar. 23, 2007 and is incorporated by reference herein in its entirety. 
       FIELD OF INVENTION 
       [0002]    The invention relates to an apparatus and a process for coating a component, in which the position of coating material sources and/or the component to be coated can be aligned. 
       BACKGROUND OF THE INVENTION 
       [0003]    During plasma spray or HVOF coating, a spray cone, i.e. the distribution of the material, is checked in order to check the alignment of nozzles. This is done by means of a steel plate which is coated and has to be removed from the coating installation and inspected. This entails an interruption to the coating process and means that the assessment of the alignment is of poor quality. 
       SUMMARY OF INVENTION 
       [0004]    It is therefore an object of the invention to provide an apparatus and a process which overcome the problem of the prior art. 
         [0005]    The object is achieved by the apparatus and the process as claimed in the claims. 
         [0006]    The subclaims list further advantageous measures, which can be combined with one another in any desired way in order to bring about further advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]    In the drawing: 
           [0008]      FIGS. 1 ,  2  show an apparatus and a process according to the prior art, 
           [0009]      FIGS. 3 ,  4 ,  5  show an apparatus according to the invention for carrying out the process according to the invention, 
           [0010]      FIG. 6  shows a gas turbine, 
           [0011]      FIG. 7  shows a perspective view of a turbine blade or vane, 
           [0012]      FIG. 8  shows a perspective view of a combustion chamber 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0013]      FIG. 1  shows a coating installation  1  according to the prior art, in which a component  4  that is to be coated is present in a holder  7 . 
         [0014]    The component  4 ,  120 ,  130 ,  155  ( FIG. 6 ,  7 ,  8 ) is coated by means of a coating material source  10 , for example by means of a plasma nozzle (LPPS, APS, VPS, etc.), a nozzle of an HVOF coating installation or from a nozzle of a cold-spraying installation or another material source (for example a PVD or CVD material source). 
         [0015]    To carry out checking by means of a spray cone, the coating material source  10  is moved into a position  13  indicated by dashed lines in  FIG. 1 . Coating material is applied to a reference plate  16 , which is removed from the coating installation  1  and can only be examined outside the coating installation  1 . 
         [0016]    This is illustrated in  FIG. 2 , in which the coated reference plate  16  is present outside the coating installation  1 . 
         [0017]    A coated surface  19 , for example a spray cone  19 , which may have deviations from a desired geometry  22  (indicated by dashed lines) of the spray cone, is present on the reference plate  16 . In the event of deviations, by way of example the coating material source  10  may have to be realigned or replaced. 
         [0018]      FIG. 3  shows an apparatus  40  according to the invention which in addition to what is shown in  FIG. 1 , as well as a reference plate  25  made from a coatable material, preferably also has a sensor  28 . The reference plate  25  is not part of the component  4 ,  120 ,  130 ,  155  ( FIG. 6 ,  7 ,  8 ) that is to be coated. The reference plate  25  can be examined in the coating installation  10  without it being necessary to open the coating apparatus  40 , in particular by means of a sensor  28 . 
         [0019]    Preferably, the reference plate  25  can be optically examined, and preferably the reference plate  25  is made from glass. 
         [0020]    The reference plate  25  is preferably made from an optically transparent material, in particular from a glass. 
         [0021]    The reference plate  25  is preferably coated and examined prior to commencement of the coating of the component  4 ,  120 ,  130 . 
         [0022]    Equally preferably, the reference plate  25  can preferably in addition be coated and examined during or after complete coating of the component  4 ,  120 ,  130 ,  155 , and retesting of the coating material source  10  is possible. 
         [0023]    The reference plate  25  can preferably also be replaced within the apparatus  40  during the coating operation. 
         [0024]    As in the prior art, the coating material source  10  is preferably moved into a position  13  (indicated by dashed lines) and coated, so as to produce a spray cone  19  on the reference plate  25 . 
         [0025]    Equally preferably, however, it is also possible to displace the reference plate  25 , i.e. for example to move it between coating material source  10  and component  4  so as to be coated ( FIG. 4 ). 
         [0026]    Then, it  25  is preferably moved back and preferably examined in a different position. 
         [0027]    The front surface  26  or rear surface  27  of the reference plate  25  can be examined by the sensor  28 . 
         [0028]    Then, the spray cone  19  on the reference plate  25  is examined within the installation  40 . This can be done by the sensor  28 , which preferably measures reflection. In a preferred exemplary embodiment, the reference plate  25  is illuminated by the sensor  28  and at the same time the reflection is recorded. 
         [0029]    Equally preferably, the reference plate  25  can be irradiated by means of an illumination source  37 , with the sensor  28  then measuring the transmission of the illumination source  37 , so that the position of the spray cone  19  can be determined. 
         [0030]    This information (see  FIG. 5 ) can preferably be presented graphically and shown to an operator of the apparatus  40  outside the apparatus  40 . The operator can manually evaluate the information. 
         [0031]    An evaluation unit  31  may preferably be present, to process and preferably assess the results from the sensor  28 . 
         [0032]    The information obtained is preferably used to realign the coating material source  10 . 
         [0033]    This alignment step can be carried out at any time during the coating process or prior to initial coating. 
         [0034]    Deviations in the spray cone  19  from the desired geometry  22  may be caused by;
       misalignment of the nozzle of the coating material source  10     wear to the nozzle of the coating material source  10     misalignment of the component  4 ,  120 ,  130 ,  155 .       
 
         [0038]    The method for evaluating the coated reference plate  25  is explained with reference to  FIG. 5 . 
         [0039]      FIG. 5  illustrates the reference plate  25  with a spray cone  19 . 
         [0040]    The illumination source  37  emits beams  34 , which in the region of the spray cone  19  cannot reach the sensor  28  behind the reference plate  26  or can do so only to an attenuated extent. The percentage transmission  40  is measured, as illustrated on the right-hand side of  FIG. 5 . 
         [0041]      FIG. 5  shows only a section through the three-dimensional geometry (x, y transmission) of the spray cone  19 . However, the three-dimensional results are preferably used for the evaluation. 
         [0042]    Misalignment of the material source  10  can be checked by means of auxiliary grid lines  29  on the reference plate  25 . 
         [0043]    The apparatus  40  and the process have the advantage that the results of the alignment can be automatically evaluated and can even be stored and archived in digitized form. It is also possible to correct the plasma parameters or the plasma nozzle by means of a knowledge database. 
         [0044]    The coating process can be interrupted if a misalignment is present, or alternatively on-time process control is possible. 
         [0045]      FIG. 6  shows, by way of example, a partial longitudinal section through a gas turbine  100 . 
         [0046]    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. 
         [0047]    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 . 
         [0048]    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  form the turbine  108 . 
         [0049]    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 . 
         [0050]    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 . 
         [0051]    A generator (not shown) is coupled to the rotor  103 . 
         [0052]    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. 
         [0053]    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. 
         [0054]    To be able to withstand the temperatures which prevail there, they may be cooled by means of a coolant. 
         [0055]    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). 
         [0056]    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 . 
         [0057]    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. 
         [0058]    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, scandium (Sc) and/or at least one rare earth element or hafnium). Alloys of this type are known from EP0 486 489 B1, EP0 786 017 B1, EP0 412 397 B1 or EP 1 306 454 A1. 
         [0059]    A thermal barrier coating, consisting for example of ZrO 2 , Y 2 O 3 —ZrO 2 , i.e. unstabilized, partially stabilized or completely stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide, may also be present on the MCrAlX. Columnar grains are produced in the thermal barrier coating by suitable coating processes, such as for example electron beam physical vapor deposition (EB-PVD). 
         [0060]    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 . 
         [0061]      FIG. 7  shows a perspective view of a rotor blade  120  or guide vane  130  of a turbomachine, which extends along a longitudinal axis  121 . 
         [0062]    The turbomachine may be a gas turbine of an aircraft or of a power plant for generating electricity, a steam turbine or a compressor. 
         [0063]    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 . 
         [0064]    As a guide vane  130 , the vane  130  may have a further platform (not shown) at its vane tip  415 . 
         [0065]    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 . 
         [0066]    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. 
         [0067]    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 . 
         [0068]    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 . 
         [0069]    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. 
         [0070]    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. 
         [0071]    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. 
         [0072]    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. 
         [0073]    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. 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). 
         [0074]    Processes of this type are known from U.S. Pat. No. 6,024,792 and EP 0 892 090 A1. 
         [0075]    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 represents 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, which are intended to form part of the present disclosure with regard to the chemical composition of the alloy. 
         [0076]    The density is preferably 95% of the theoretical density. 
         [0077]    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). 
         [0078]    The layer preferably has a composition Co-30Ni-28Cr-8Al-0.6Y-0.7Si or Co-28Ni-24Cr-10Al-0.6Y. In addition to these cobalt-based protective coatings, it is also preferable to use 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. 
         [0079]    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. 
         [0080]    The thermal barrier coating covers the entire MCrAlX layer. Columnar grains are produced in the thermal barrier coating by means of suitable coating processes, such as for example electron beam physical vapor deposition (EB-PVD). 
         [0081]    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. 
         [0082]    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. 
         [0083]    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  418  (indicated by dashed lines). 
         [0084]      FIG. 8  shows a combustion chamber  110  of a gas turbine. The combustion chamber  110  is configured, for example, as what is known as an annular combustion chamber, in which a multiplicity of burners  107 , which generate flames  156 , arranged circumferentially around the axis of rotation  102  open out into a common combustion chamber space  154 . For this purpose, the combustion chamber  110  overall is of annular configuration positioned around the axis of rotation  102 . 
         [0085]    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 . 
         [0086]    On the working medium side, each heat shield element  155  made from an alloy is equipped with a particularly heat-resistant protective layer (MCrAlX layer and/or ceramic coating) or is made from material that is able to withstand high temperatures (solid ceramic bricks). 
         [0087]    These protective layers may be similar to the turbine blades or vanes, i.e. for example 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 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. 
         [0088]    It is also possible for a, for example, ceramic thermal barrier coating to be present on the MCrAlX, 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. 
         [0089]    Columnar grains are produced in the thermal barrier coating by means of suitable coating processes, such as for example electron beam physical vapor deposition (EB-PVD). 
         [0090]    Other coating processes are possible, e.g. atmospheric plasma spraying (APS, LPPS, VPS) or CVD. The thermal barrier coating may include grains that are porous or contain micro-cracks or macro-cracks, in order to improve the resistance to thermal shocks. 
         [0091]    Refurbishment means that after they have been used, protective layers may have to be removed from heat shield elements  155  (e.g. by sand-blasting). Then, the corrosion and/or oxidation layers and products are removed. If appropriate, cracks in the heat shield element  155  are also repaired. This is followed by recoating of the heat shield elements  155 , after which the heat shield elements  155  can be reused. 
         [0092]    Moreover, a cooling system may be provided for the heat shield elements  155  and/or their holding elements, on account of the high temperatures in the interior of the combustion chamber  110 . The heat shield elements  155  are then, for example, hollow and may also have cooling holes (not shown) opening out into the combustion chamber space  154 .