Abstract:
By continuously long engravings, the spallation behavior of the thermal barrier coating is reduced and the lifetime of the TBC is prolonged.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Application No. PCT/EP2015/075390, having a filing date of Nov. 2, 2015, based off of European application No. EP 14195844.7 having a filing date of Dec. 2, 2014, the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    This following relates to a ceramic surface structure, wherein a long engraving is present along a row of cooling holes. 
       BACKGROUND 
       [0003]    The highly loaded turbine blades and vanes require the application of different protection technologies in order to be able to withstand the high thermal loading. The front stages of the turbine blades and vanes require a ceramic coating and the film cooling technology as well as the internal cooling. 
         [0004]    The application of such technologies is helpful as long as the combination works during operation and no spallation occurs or nor cooling holes blockage is noticed. 
         [0005]    The manufacturing of the film cooling holes could be one of the reasons for the ceramic coating spallation. 
         [0006]    Parameters of the laser drilling causes cracks within the ceramic coating, which later spalls down and restricts the operation of the component. 
         [0007]    On the other hand it is not possible to reduce the laser drilling energy to a very low level due to the fact that no drilling will take place with low energy. 
       SUMMARY 
       [0008]    An aspect relates to improving the lifetime of a ceramic coating and preventing the overall spallation of a TBC. 
     
    
     
       BRIEF DESCRIPTION 
         [0009]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0010]      FIG. 1  depicts a view on top of a surface of a TBC and a row of cooling holes, in accordance with embodiments of the present invention; 
           [0011]      FIG. 2  depicts a cross-section area of  FIG. 1 , in accordance with embodiments of the present invention; 
           [0012]      FIG. 3  depicts a view of a first embodiment of a curved form of an engraving, in accordance with embodiments of the invention; and 
           [0013]      FIG. 4  depicts a view of a second embodiment of a curved form an engraving, in accordance with embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    By an implementation of a polymer masking it is possible to introduce the suggested design in  FIGS. 1-4 . The polymer masking will provide a ceramic free region along the cooling holes. 
         [0015]    This manufacturing procedure has following advantage: 
         [0016]    The engraving will not reduce the bond coat thickness as during a laser engraving 
         [0017]    This step can be carried out during the coating 
         [0018]    In case of casting and coating deviations, the polymer masking will not affect the bond coat thickness. 
         [0019]    The width of such a ceramic free region could vary between 1 and 2 mm. 
         [0020]    The positive effect of the engraving is the spallation behavior. In case of spallation the spalled region will not be extended on wide regions. 
         [0021]    Another positive effect of the engraving is the vortices introduced due to the no-APS regions, which forces the hot gas flow to stick to the wall as by the dimples on a golf ball. During operation the step within the ceramic coating will be smoothened as well as the APS smoothening procedure will help breaking the edges. 
         [0022]    The following positive effects are related to the engraving: 
         [0023]    Retrofitable with current designs 
         [0024]    In case of spallation, only restricted region will be affected 
         [0025]    Lower operation risk 
         [0026]    Reduced rework after laser drilling 
         [0027]    Applicable to all spallation threatened cooling holes rows 
         [0028]    Applicable to vanes and blades. 
         [0029]      FIG. 1  shows a view on the top of a ceramic coating  25  ( FIG. 2 ). The thermal barrier coating  25  (TBC) is part of a component  1  which has a substrate  22  ( FIG. 2 ) wherein on top of the substrate  22  the thermal barrier coating  25  is applied. This component  1  has at least one row  7  of cooling holes  10 ′,  10 ″, . . . , which are during use of the component  1  overflowed by hot gas according the arrow  13 , especially almost perpendicular to the direction  14  of the row  7 . The direction  14  is straight or has only one or two times a break of slope of maximum 25°. 
         [0030]    Along the direction  14  of the row  7  of the cooling holes  10 ′,  10 ″, . . . there is especially only before the row  7  an engraving  16  and/or after the row  7  a second engraving  19 . 
         [0031]    These engravings  16 ,  19  are continuous, especially straight engravings in the TBC  25 . 
         [0032]    The engravings  16 ,  19 ,  20 ,  116 ,  216 ,  31  ( FIG. 3, 4 ) are not endless, e. g. not a circle or not a square or not closed looped. 
         [0033]    The engravings  16 ,  19 ,  20 ,  116 ,  216 ,  31  start especially at the beginning and end at the end of a row  7 . 
         [0034]    The distance between two engravings  16 ,  19 ,  20 ,  116 ,  216 ,  31  before and after the one row  7  next to each other is especially 1 mm to 2 mm. 
         [0035]    Furthermore the engravings can also arranged only in the TBC  25 . 
         [0036]    In  FIG. 2  it can be seen that the engravings  16 ,  19  have a depth until the substrate  22 . 
         [0037]    But nevertheless the surface of the substrate  22  can be coated with a metallic bond coat like a NiCoCrAl plus optional additives (Y, Re, Si, Ta, . . . ). 
         [0038]      FIGS. 3, 4  show a curved form of the engravings  20 ,  116 ,  216 ,  31 , wherein the distance of opposite curved engraving  116 ,  20 ;  216 ,  31  is smaller between two cooling holes  10 ′,  10 ″ and which are not straight ( FIG. 4 ), but multiple curved or a combination of it ( FIG. 3 ). 
         [0039]    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. 
         [0040]    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.