Abstract:
The invention relates to a peening device for peening a component with a part to be peened and a part not to be peened. The peening device comprises a chamber with at least one opening located therein, wherein the opening is dimensioned in such a manner that the part not to be peened of the component can be guided there through, and a fixture for retaining the component which features a section which entirely covers the opening of the chamber when the part not to be peened is at least partially guided into said opening, and said section completely encloses the part not to be peened of the component between the adjacent region of the part to be peened of the component and the opening.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US National Stage of International Application No. PCT/EP2007/053628, filed Apr. 13, 2007 and claims the benefit thereof. The International Application claims the benefits of European application No. 06010927.9 filed May 26, 2006, both of the applications are incorporated by reference herein in their entirety. 
     FIELD OF INVENTION 
     The present invention relates to a peening device for peening a component having a part to be peened and a part not to be peened. 
     BACKGROUND OF THE INVENTION 
     In a peening method, a peening product is thrown at high velocity against that surface of a component which is to be treated, the work outcome to be achieved being obtained. One example of a peening process is shot peening which is a special instance of strain hardening peening. In shot peening, small balls are thrown by means of spinner, compressed air or injector peening plants onto the surface to be treated. The impingement of the peening product at high velocity results in an elastoplastic deformation in the region of the surface, this giving rise to internal compressive stresses in the workpiece which lead to strain hardening in the region of the surface of the peened component portion. Another example of a peening process is sandblasting, in which, for example, corundum grains are thrown onto the surface to be treated, in order to strip off or roughen up surface regions. 
     When only specific regions of a component are to be peened, as a rule, the regions not to be peened are protected by means of a masking. Thus, for example, it is customary, in the case of turbine blades which have a blade foot, a blade leaf and a blade platform arranged between the blade foot and the blade leaf, to subject the blade foot and that side of the blade platform which faces the blade foot to a shot peening process in order to increase their strength. The remaining sides of the blade platform and also the blade leaf in this case are not subjected to the shot peening process, since this would lead to an impairment of the high-temperature properties. The masking of those parts of the turbine blade which are not to be subjected to the shot peening process is carried out by hand and is therefore labor and cost intensive. 
     SUMMARY OF INVENTION 
     The object of the present invention is to provide a peening device which allows a less labor and cost intensive preparation of components which have portions to be peened and not to be peened. 
     This object is achieved by means of a peening device as claimed in the claims. The dependent claims contain advantageous refinements of the peening device according to the invention. 
     A peening device according to the invention for peening a component having a part to be peened and a part not to be peened comprises a chamber with at least one orifice arranged in it, the orifice being dimensioned in such a way that that part of the component which is not to be peened can be led at least partially through it. Moreover, a mounting for holding the component is present. This mounting has a portion which, when that part of the component which is not to be peened is led at least partially through, completely covers the orifice in the chamber and completely surrounds that part of the component which is not to be peened between that region adjacent to that part of the component which is to be peened and the orifice. 
     The component inserted into the mounting can then be arranged in the chamber in such a way that the part not to be peened is for the most part located outside the chamber so as to be inaccessible to the peening product. In this case, the part not to be peened is protected, where it projects into the chamber, by the mounting which completely surrounds the part which projects into the chamber and is not to be peened. A complicated masking of that part of the component which is not to be peened may be dispensed with. 
     Advantageously, the chamber has a chamber bottom in which the at least one orifice is arranged. 
     In this refinement, that part of the component which is not to be peened can be led in the vertical direction through the orifice. Shot peening can then take place from the side of the component, and the peening product can flow off from the component and the mounting toward the chamber bottom, so that the outlets for the peening product are not blocked by peening product. 
     The peening device may be configured, in particular, as a peening device for peening a part of a turbine blade with a blade leaf, with a blade foot and with a blade platform arranged between the blade leaf and the blade foot. That part of the component which is to be peened is then formed by the blade foot and by that side of the blade platform which faces the blade foot. That part of the component which is not to be peened is then formed by the blade leaf and by those sides of the blade platform which do not face the blade foot. In this refinement, the dimensions of the orifice in the chamber are selected in such a way that the blade leaf can be led at least partially through the orifice. Moreover, the mounting is configured in such a way that it completely surrounds the turbine blade at least in the region of the edge of the blade platform. In comparison with a peening device according to the prior art, the turbine blade can be peened at a lower outlay in terms of labor and of costs by means of the device according to the invention, since the masking of the entire blade leaf and of a large part of the blade platform is dispensed with. By contrast, the insertion of the turbine blade into the mounting and the closing of the orifice by means of the mounting are very much less labor and cost intensive. Moreover, the material consumption is lower, since, in contrast to masking, no material which could not be reused is employed. 
     Moreover, the mounting may have a region on which that side of the blade platform which faces the blade leaf lies when the blade is held. Thus, the turbine blade can be supported by the mounting, particularly when the orifice is arranged in the chamber bottom, so that a reliable support of the turbine blade and consequently a reliable positioning can be achieved without further aids. 
     In an advantageous refinement of the peening device, the orifice may be surrounded by a margin projecting toward the chamber interior. What may be achieved by this refinement is that the blade foot is at such a great distance from the wall or the bottom of the chamber that the directions from which the peening product can reach the blade foot are not appreciably restricted by the near wall or the near bottom. 
     The mounting may additionally comprise a cap, which is designed to be placed onto that end of the blade foot which faces away from the blade leaf. By means of the cap, any inlet orifices, arranged in the blade foot, of cooling air ducts can be protected against the penetration of peening product. The cap can be connected or connectable to the mounting, particularly in such a way that, with the turbine blade held by the mounting, the connection is located at a distance from the blade foot in the region of the narrow sides of the blade foot. A highly stable arrangement of the cap can thus be achieved, without the accessibility of the blade foot for the peening product being appreciably restricted. 
     For the prevention of peening product deposits which in the course of the peening process could impair the free access of the peening product to the surface to be peened, the mounting may have discharge surfaces and/or discharge ducts for discharging the peening product. In particular, when the orifice is arranged in the chamber bottom, a rapid discharge of the peening product in the direction of the chamber bottom can thereby be brought about, utilizing the force of gravity. 
     The chamber is advantageously designed as a vacuum chamber, so that, on the one hand, the peening process is not impaired by air in the chamber and, on the other hand, an escape of peening product from the chamber in the event of a leakage point can be counteracted. 
     The peening device according to the invention may, in particular, be designed as a peening device for carrying out a shot peening process, that is to say as a shot peening device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features, properties and advantages of the present invention may be gathered from the following description of an exemplary embodiment, with reference to the accompanying figures. 
         FIG. 1  shows by way of example a gas turbine in a longitudinal part section. 
         FIG. 2  shows a perspective view of a moving blade or guide blade of a turbomachine. 
         FIG. 3  shows a combustion chamber of a gas turbine. 
         FIG. 4  shows diagrammatically a peening device according to the invention in a sectional side view. 
         FIG. 5  shows a detail from  FIG. 4  in a sectional side view. 
         FIG. 6  shows the detail from  FIG. 5  in a section perpendicular to the section from  FIG. 5 . 
         FIG. 7  shows a modification of the detail shown in  FIG. 5 . 
         FIG. 1  shows by way of example a gas turbine  100  in a longitudinal part section. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The gas turbine  100  has inside it a rotor  103  rotary-mounted about an axis of rotation  102  and having a shaft  101 , said rotor also being designated as a turbine rotor. 
     An intake casing  104 , a compressor  105 , a, for example, toroidal combustion chamber  110 , in particular annular combustion chamber, with a plurality of coaxially arranged burners  107 , a turbine  108  and the exhaust gas casing  109  succeed one another along the rotor  103 . 
     The annular combustion chamber  110  communicates with a, for example, annular hot-gas duct  111 . There, for example, four turbine stages  112  connected in series form the turbine  108 . 
     Each turbine stage  112  is formed, for example, from two blade rings. As seen in the direction of flow of a working medium  113 , a guide blade row  115  is followed in the hot-gas duct  111  by a row  125  formed from moving blades  120 . 
     The guide blades  130  are in this case fastened to an inner casing  138  of a stator  143 , whereas the moving blades  120  of a row  125  are attached to the rotor  103 , for example, by means of a turbine disk  133 . 
     A generator or a working machine (not illustrated) is coupled to the rotor  103 . 
     When the gas turbine  100  is in operation, air  135  is sucked in by the compressor  105  through the intake casing  104  and is compressed. The compressed air provided at the turbine-side end of the compressor  105  is routed to the burners  107  and mixed there with a fuel. The mixture is then burnt in the combustion chamber  110  so as to form the working medium  113 . The working medium  113  flows from there along the hot-gas duct  111  past the guide blades  130  and the moving blades  120 . At the moving blades  120 , the working medium  113  expands so as to transmit a pulse, so that the moving blades  120  drive the rotor  103  and the latter drives the working machine coupled to it. 
     The components exposed to the hot working medium  113  undergo thermal loads while the gas turbine  100  is in operation. The guide blades  130  and moving blades  120  of the first turbine stage  112 , as seen in the direction of flow of the working medium  113 , are subjected to the highest thermal load, in addition to the heat shield elements lining the annular combustion chamber  110 . 
     In order to withstand the temperatures prevailing there, these may be cooled by means of a coolant. 
     Substrates of the components may also have a directional structure, that is to say they are monocrystalline (SX structure) or have only longitudinally directed grains (DS structure). 
     Materials used for the components, particularly for the turbine blade  120 ,  130  and components of the combustion chamber  110 , are, for example, iron-, nickel- or cobalt-based superalloys. 
     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; these publications are part of the disclosure with regard to the chemical composition of the alloys. 
     The blades  120 ,  130  may also have coatings against corrosion (MCrAlX; M is at least one element of the group 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). 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 regard to the chemical composition. 
     A heat insulation layer may also be present on the MCrAlX and consists, for example, of ZrO 2 , Y 2 O 3 —ZrO 2 , that is to say it is not stabilized or is partially or completely stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide. 
     Columnar grains are generated in the heat insulation layer by means of suitable coating methods, such as, for example, electron beam evaporation (EB-PVD). 
     The guide blade  130  has a guide blade foot (not illustrated here), facing the inner casing  138  of the turbine  108 , and a guide blade head lying opposite the guide blade foot. The guide blade head faces the rotor  103  and is secured to a fastening ring  140  of the stator  143 . 
       FIG. 2  shows a perspective view of a moving blade  120  or guide blade  130  of a turbomachine, said blade extending along a longitudinal axis  121 . 
     The turbomachine may be a gas turbine of an aircraft or of a power station for electricity generation, a steam turbine or a compressor. 
     The blade  120 ,  130  has successively along the longitudinal axis  121  a fastening region  400 , a blade platform  403  adjacent thereto and also a blade leaf  406  and a blade tip  415 . 
     As a guide blade  130 , the blade  130  may have a further platform at its blade tip  415  (not illustrated). 
     In the fastening region  400 , a blade foot  183  is formed which serves for fastening the moving blades  120 ,  130  to a shaft or a disk (not illustrated). 
     The blade foot  183  is configured, for example, as a hammer head. Other configurations as a pinetree or dovetail foot are possible. 
     The blade  120 ,  130  has a leading edge  409  and a trailing edge  412  for a medium which flows past the blade leaf  406 . 
     In conventional blades  120 ,  130 , for example, solid metallic materials, in particular superalloys, are used in all regions  400 ,  403 ,  406  of the blade  120 ,  130 . 
     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; these publications are part of the disclosure with regard to the chemical composition of the alloy. 
     The blade  120 ,  130  may in this case be manufactured by means of a casting method, also by means of directional solidification, by means of a forging method, by means of a milling method or combinations thereof. 
     Workpieces with a monocrystalline structure or structures are used as components for machines which are exposed during operation to high mechanical, thermal and/or chemical loads. 
     The manufacture of monocrystalline workpieces of this type takes place, for example, by directional solidification from the melt. These are casting methods in which the liquid metallic alloy solidifies to the monocrystalline structure, that is to say to the monocrystalline workpiece, or directionally solidifies. 
     In this case, dendritic crystals are oriented along the heat flow and form either a columnar-crystalline grain structure (columnar, that is to say grains which run over the entire length of the workpiece and here, according to general linguistic practice, are designated as being directionally solidified) or a monocrystalline structure, that is to say the entire workpiece consists of a single crystal. These methods have to avoid the transition to globulitic (polycrystalline) solidification, since undirected growth necessarily produces transverse and longitudinal grain boundaries which nullify the good properties of the directionally solidified or monocrystalline component. 
     When directionally solidified structures are referred to in general terms, this means both monocrystals which have no grain 
     boundaries or, at most, small-angle grain boundaries and columnar-crystal structures which have grain boundaries running in the longitudinal direction, but no transverse grain boundaries. With regard to these second-mentioned crystalline structures, directionally solidified structures are also referred to. 
     Such methods are known from U.S. Pat. No. 6,024,792 and EP 0 892 090 A1; these publications are part of the disclosure with regard to the solidification method. 
     The blades  120 ,  130  may also have coatings against corrosion or oxidation, for example (MCrAlX; M is at least one element of the group 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)). 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 regard to the chemical composition of the alloy. 
     The density preferably lies at 95% of the theoretical density. 
     A protective aluminum oxide layer (TGO=thermal grown oxide layer) forms on the MCrAlX layer (as an intermediate layer or as the outermost layer). 
     A heat insulation layer may also be present on the MCrAlX and is preferably the outermost layer and consists, for example, of 
     ZrO 2 , Y 2 O 3 —ZrO 2 , that is to say it is not stabilized or is partially or completely stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide. 
     The heat insulation layer covers the entire MCrAlX layer. 
     Columnar grains are generated in the heat insulation layer by means of suitable coating methods, such as, for example, electron beam evaporation (EB-PVD). 
     Other coating methods may be envisaged, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The heat insulation layer may have porous, microcrack- or macrocrack-compatible grains for better thermal shock resistance. The heat insulation layer is therefore preferably more porous than the MCrAlX layer. 
     Refurbishment means that components  120 ,  130 , after use, must, where appropriate, be freed of protective layers (for example, by sandblasting). A removal of the corrosion and/or oxidation layers or products then takes place. If appropriate, cracks in the component  120 ,  130  are also repaired. This is followed by a recoating of the component  120 ,  130  and a renewed use of the component  120 ,  130 . 
     The blade  120 ,  130  may be of hollow or solid design. If the blade  120 ,  130  is to be cooled, it is hollow and, if appropriate, also has film cooling holes  418  (indicated by dashes). 
       FIG. 3  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  arranged around an axis of rotation  102  in the circumferential direction issue into a common combustion chamber space  154  and generate flames  156 . For this purpose, the combustion chamber  110  is configured as a whole as an annular structure which is positioned around the axis of rotation  102 . 
     To achieve a comparatively high efficiency, the combustion chamber  110  is designed for a comparatively high temperature of the working medium M of about 1000° C. to 1600° C. In order to make it possible to have a comparatively long operating time even under these operating parameters which are unfavorable for the materials, the combustion chamber wall  153  is provided on its side facing the working medium M with an inner lining formed from heat shield elements  155 . 
     Each heat shield element  155  consisting of an alloy is equipped on the working-medium side with a particularly heat-resistant protective layer (MCrAlX layer and/or ceramic coating) or is manufactured from material resistant to high temperature (solid ceramic rocks). 
     These protective layers may be similar to those of the turbine blades, that is to say, for example, MCrAlX means: M is at least one element of the group 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). 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 regard to the chemical composition of the alloy. 
     A, for example, ceramic heat insulation layer may also be present on the MCrAlX and consists, for example, of ZrO 2 , Y 2 O 3 —ZrO 2 , that is to say it is not stabilized or is partially or completely stabilized by yttrium oxide and/or calcium oxide and/or magnesium oxide. 
     Columnar grains are generated in the heat insulation layer by means of suitable coating methods, such as, for example, electron beam evaporation (EB-PVD). 
     Other coating methods may be envisaged, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The heat insulation layer may have porous, microcrack- or macrocrack-compatible grains for better thermal shock resistance. 
     Refurbishment means that heat shield elements  155 , after being used, must, where appropriate, be freed of protective layers (for example, by sandblasting). A removal of the corrosion and/or oxidation layers or products then takes place. If appropriate, cracks in the heat shield element  155  are also repaired. A recoating of the heat shield elements  155  and a renewed use of the heat shield elements  155  then follow. 
     Moreover, on account of the high temperatures inside the combustion chamber  110 , a cooling system may be provided for the heat shield elements  155  or for their holding elements. The heat shield elements  155  are then, for example, hollow and, if appropriate, also have cooling holes (not illustrated) issuing into the combustion chamber space  154 . 
     An exemplary embodiment of the device according to the invention for peening a component is illustrated diagrammatically in  FIG. 4  in a sectional side view. The peening device  1  is configured as a shot peening device for shot peening the blade feet of turbine blades  2 . It comprises a vacuum chamber  5  in which pressure can be reduced with respect to the ambient pressure by means of a connected vacuum pump  7 . In the chamber bottom  9  of the vacuum chamber  5 , orifices are present, through which the blade leaves  3  of the turbine blades  2  can be inserted, so that they project out of the vacuum chamber  5 . 
     An orifice  11  in the chamber bottom  9  and a turbine blade  2 , the blade leaf  3  of which is inserted through the orifice  11 , are shown in a sectional view in  FIG. 5 . A sectional view, perpendicular to the section from  FIG. 5 , of the same turbine blade  2  and of the same orifice  11  is shown in  FIG. 6 . 
     The orifice  11  is surrounded by a wall  13  which projects toward the inside of the vacuum chamber  5  and which forms a nipple-like element  12  around the orifice  11 . A mounting  14  with a turbine blade  2  is inserted into the orifice  11   a  of the nipple  12 . The mounting comprises two parts, to be precise an inner element  15  and an outer element  27 . The inner element  15  is inserted into the orifice  11   a  of the nipple  12 . For this purpose, a portion  17  of the inner element  15  has an external dimension which corresponds to the internal dimension of the nipple  12 , so that the inner element  15  can be inserted with an exact fit into the orifice  11   a . Furthermore, the inner element  15  has a bearing portion  19  on which the blade platform  21  of the turbine blade  2  can lie. Located at the center of the bearing portion  19  is a leadthrough orifice  23  through which the blade leaf  3  can be led through the inner element  15  of the mounting  14 . 
     The inner element  15  is in this case configured in such a way that it completely surrounds the edge  25  of the blade platform  21 , that side of the blade platform  21  which faces the blade leaf  3  and a portion, adjacent to the blade platform  21 , of the blade leaf  3 . In particular, the dimensions of the bearing portion  19  and of the leadthrough orifice  23  may be designed such that they form an exactly fitting bearing surface or leadthrough for the turbine blade  2 . 
     The inner element  15  and consequently the turbine blade  2  are secured by means of the outer element  27  which is slipped over the inner element  15  and which has a portion which comes to bear against the outside of the wall  13 . The portion  29  is in this case configured in such a way that it bears closely against the outside of the wall  13 . Moreover, a tension device may preferably be present, by means of which the inner element  15  and the outer element  27  can be braced with respect to one another in such a way that the mounting  14  is secured with a clamping fit on the nipple  12  in the region of the orifice  11   a.    
     The outer element  27  does not reach as far as the blade foot  31  on the wide side of the blade  2  (cf.  FIG. 5 ). Only on the narrow sides of the blade  2  are located holding portions  33  which reach up to the blade foot  31  and which engage from above onto the blade platform  33  and thus fix the blade platform  21  on the bearing portion  19  of the inner element  16 . 
     Moreover, the outer element  27  has a stirrup  35  having an upper part  37  which bears with an exact fit against the top side of the blade foot  31  when the outer element  27  is placed onto an inner element  15  having a blade  2  arranged in it. The upper part  37  of the stirrup  35  forms a cap which seals off inlet orifices for cooling air into internal cooling air ducts of the turbine blade  2  against the penetration of peening product  4 . So that the blade foot  31  remains accessible to the peening product everywhere, the stirrup  35  is configured such that, except on the top side of the blade foot  31 , it runs at a distance from the blade foot  31  when a turbine blade  2  is held by the mounting  14 . 
     On account of the nipple  12  and the overall height of the mounting  14 , the blade foot  31  of a turbine blade  2  is at a sufficient distance from the chamber bottom  9 , so that it is also possible to peen the blade foot from a direction inclined with respect to the chamber bottom. As a result, for example, curved portions  32  of turbine blades  2  can be peened with peening product  4  such that the peening product  4  can impinge onto all the surface regions essentially perpendicularly. 
     The mounting  14  is configured with as few horizontal surfaces as possible, so that the peening product  4  can run off, unimpeded, from the mounting in the direction of the chamber bottom  9 . Peening product deposits can thus be largely avoided. 
     During a peening process, the orifice  11  is closed completely by the mounting  14  and the turbine blade  2  arranged in it, so that the blade leaf  3  projecting out of the vacuum chamber  5  is not accessible for the peening product  4 . Those portions of the blade leaf  3  which are surrounded completely by the mounting  14  are protected by the latter against peening product. The same applies to the blade platform. 
     The introduction of a turbine blade  2  into the vacuum chamber  5  may take place in that the upper part  39  of the vacuum chamber  5  is removed. All the chamber orifices  11  thereby become accessible. Then, first, the inner element  15  of the mounting  14  is placed onto the nipple  12 . The turbine blade  2  is then led with the blade leaf  3  through the passage orifice  23  of the inner element  15 , so that the blade platform  21  comes to bear on the bearing portion  19 . The outer element  27  is subsequently put in place and is braced against the inner element  15  in order to ensure a secure hold of the turbine blade  2 . 
     With the outer element  27  put in place, the top side of the blade foot  31  is then protected by the upper part  37  of the stirrup portion  35  of the outer element  27 . Moreover, the upper part  37  of the stirrup portion may have tenons which engage into the cooling air inlet orifices in the blade foot  31 . 
     The bracing of the outer element  27  against the inner element  15  may take place, for example, by means of screw or snap connections. It is also possible, however, to press the outer element  27  onto the inner element  15  from above, this purpose being served by a rod  41  which can engage into a notch  43  formed in the upper part  37 . By pressure on the rod  41 , the outer element  27  can be pressed firmly onto the inner element  15 . 
     A modification of the exemplary embodiment of the peening device described with reference to  FIGS. 5 and 6  is illustrated in  FIG. 7 . The sectional view shown in  FIG. 7  corresponds to the sectional view from  FIG. 5 . The vacuum chamber  55  differs from the vacuum chamber  5  of the first design variant in that the orifice  11  in the chamber bottom  9  is not surrounded by a nipple  12 . In this embodiment, the inner element  15  is inserted directly into the orifice  11 . By means of an outer element  47  which corresponds essentially to the outer element  37  of the first design variant, the inner element  15 , together with a turbine blade  2  inserted in it, is secured. The outer element  47  differs from the outer element  37  merely in that the portion  29  coming to bear against the outside of the nipple  12  is absent. Instead, the outer element  47  is pressed directly onto the chamber bottom  9 , for example, by means of the rod  41 . 
     In the design variant described, the distance of the blade foot  31  from the chamber bottom  9  is markedly shorter than in the first variant. However, depending on the design of the blade foot  31  and on the peening process used, this shorter distance may also be sufficient to be able to peen, in particular shot peen, the blade foot  31 . The design variant illustrated in  FIG. 7  otherwise does not differ from the design variant illustrated in  FIGS. 5 and 6 . 
     It may be noted at this juncture that, contrary to what is illustrated in the exemplary embodiment, the orifice  11  may basically also be arranged in a side wall or in the ceiling of the vacuum chamber. The advantage of arranging the orifice in the chamber bottom, however, is that the insertion of the turbine blade  2  into the mounting is simpler than in the other variants, since even the force of gravity leads to the blade being fixed in position after the latter has been inserted into the inner element, whereas, in the other variants, measures have to be taken in order to fix the blade  2  until the outer element of the mounting has assumed fixing.