Abstract:
Remelting during deposition welding of layers ( 7, 7′, 7″ ) enables a desired micro structure ( 10′ ) having enlarged grains to be controlled, which leads to improved properties at high temperatures.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a 35 U.S.C. §§371 national phase conversion of PCT/EP2013/077403, filed Dec. 19, 2013, which claims priority of European Application No. 13151884.7, filed Jan. 18, 2013, the contents of which are incorporated by reference herein. The PCT International Application was published in the German language. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to the remelting of deposition weld layers. 
       TECHNICAL BACKGROUND 
       [0003]    For components which are subject to load when they are in service, such as is known in the context of gas turbines for turbine blades, repair welds are performed, in which material is deposited. This can be done by laser deposition welding. Also known is laser beam remelting, in which cracks are remelted without deposition of material. 
         [0004]    Deposition-welded layers often do not have the desired microstructure, in particular for the high-temperature properties. 
         [0005]    It is an object of the invention, therefore, to solve the aforementioned problem. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIGS. 1A-3  show steps of the method for remelting in deposition welding of the component according to the invention, 
           [0007]      FIG. 4  shows a list of superalloys. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0008]    The figures and the description represent only exemplary embodiments of the invention. 
         [0009]      FIG. 1A  shows, as the starting point, a component  1  with a substrate  4 , on which is present a deposition weld  8  consisting of a deposition-welded layer  7 . 
         [0010]    The substrate  4  is metallic and, in the case of gas turbine components, is preferably a nickel-based or cobalt-based superalloy, in particular as shown in  FIG. 4 . 
         [0011]    The deposition weld  8 , which was preferably created by laser deposition welding, is present on a surface  13  of the substrate  4 . 
         [0012]    The material of the deposition weld  8  may correspond to or be similar to the material of the substrate  4 . 
         [0013]    Referring to  FIG. 1B , in order to increase grain size and to reduce the number of grain boundaries perpendicular to a direction of load, the surface  16 ′ of the deposition weld  8  is treated with a laser beam, such that there results, within the welded layer  7 , a remelt region  10  with a surface  16 ″, as shown in  FIG. 1B . 
         [0014]      FIG. 2  shows another exemplary embodiment of the invention, in which multiple deposition-welded layers  7 ′,  7 ″,  7 ″′ are already present on the substrate  4  on the surface  13  of the latter, and there form the deposition weld  8 ′. 
         [0015]    Only after multiple deposition-welded layers  7 ′,  7 ″,  7 ″′ are present is the remelting process carried out in order to generate a remelt region  10 ′ which then extends over one, in particular two, very particularly over multiple deposition-welded layers  7 ″′,  7 ″. 
         [0000]    Preferably, not all of the deposition-welded layers  7 ′,  7 ″,  7 ″′ are encompassed. 
         [0016]    This is then in particular the case when the height of the deposition-welded layers  7 ′,  7 ″,  7 ″′ is less than the target remelt depth of the remelt region  10 ′. 
         [0017]    Referring to  FIG. 3 , it is equally possible, on a remelt region  10 ″ within a deposition-welded layer  7   IV , to deposit a further deposition-welded layer  7   V  with a surface  16   IV  which, with respect to grain size formation, attaches to the grain size of the remelt region  10 ″ ( FIG. 3 ) and which is preferably not remelted. 
         [0018]    The remelt region  10 ′,  10  ( FIGS. 1 ,  2 ) or a deposition weld  7   V  as shown in  FIG. 3  can then represent the outermost surface  16 ″,  16 ″′,  16   IV  onto which metallic protective layers (MCrAlX, PtAl, . . . ) and/or ceramic thermal barrier coatings (ZrO 2 -Y 2 O 3 ) are then deposited in a known manner. 
         [0019]    Preferably, this method is suitable for substrates  4  solidified in a polycrystalline manner ( FIGS. 1-3 ).