Abstract:
The use of a laser beam, which has an external and an internal laser beam area with different intensities allows a higher temperature gradient to be produced along the z direction, is provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Application No. PCT/EP2014/053072 having a filing date of Feb. 18, 2014 based off of EP Application No. 13158179.5 having a filing date of Mar. 7, 2013, the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The following relates to lasering in which a laser beam that has two different laser beam areas is used. 
       BACKGROUND 
       [0003]    Laser welding methods for remelting cracks or for deposition welding on a substrate are state of the art. 
         [0004]    When welding, there is generally the problem that cracks can occur within remelted material or deposition welding. 
         [0005]    This has so far been solved by the entire component being preheated. 
         [0006]    In the case of monocrystalline rewelding or monocrystalline deposition welding, one object is to produce a temperature zone with a temperature gradient in which the Z component dominates the other two components at the solidification front. 
         [0007]    In addition, the temperature zone should be designed such that thermal compressive stresses are produced in the trailing area. 
       SUMMARY 
       [0008]    An aspect relates to a method and a device with which this can be made easier. 
         [0009]    Embodiments of the invention simplify the operative and procedural preheating during welding and the production of temperature zones that are conducive to monocrystalline growth. 
     
    
     
       BRIEF DESCRIPTION 
         [0010]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0011]      FIG. 1  schematically shows an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The FIGURE and the description represent only exemplary embodiments of the invention. 
         [0013]    In the FIGURE, an intensity distribution of a laser beam  1  is shown. 
         [0014]    An internal laser beam area  7  is arranged non-concentrically in relation to an external laser beam area  4 . 
         [0015]    Inside a laser beam  1  there is an internal laser beam area  7 , which has a higher intensity or a higher power output, particularly of 30-1000 W/mm 2 , most particularly 100-300 W/mm 2 , and can remelt a crack or can melt material for deposition welding. 
         [0016]    The internal laser beam area  7  is surrounded, preferably completely, by an external laser beam area  4 , which has a greater cross section, particularly a greater diameter, and has a lower intensity or a lower laser output, so that the external laser beam area  4  only pre-heats and post-heats the area before and after the internal laser beam area  7 . 
         [0017]    The diameter of the internal laser beam area  7  is preferably 1 mm and that of the external laser beam area  4  is 4 mm. 
         [0018]    The internal area  7  is preferably arranged non-concentrically in the external laser beam area  4 . 
         [0019]    This intensity distribution has the effect of increasing the temperature gradient in the radiating direction of the laser beam  1  and such a laser beam  1  can preferably be used in monocrystalline remelting or deposition welding. 
         [0020]    An example of a substrate that has a directionally solidified structure is PWA 1483SX, which produces a monocrystalline structure. 
         [0021]    The ratio of the intensities or the outputs of the laser beam areas  4 ,  7  in relation to one another is at least 1.5, in particular at least 2. 
         [0022]    The surface area of the internal laser beam area  7  is preferably a maximum of 25% of the external laser beam area  4 . 
         [0023]    Seen in the running direction  23  of the laser beam  1 , the internal laser beam area  7  is closer to the remelting area. 
         [0024]    Seen in the running direction  23  of the laser beam  1 , the internal laser beam area  7  is arranged in front, that is to say impinges first on the substrate  20 . 
         [0025]    The internal laser beam area  7  may be arranged with its periphery at the periphery  9  of the external laser beam area  4  (not represented) or be at a distance from the edge of the external laser beam area  4 . 
         [0026]    Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. 
         [0027]    For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.