Layer System with Diffusion Inhibiting Layer

Abstract

The lifespan of a layer system at high temperatures is determined by the diffusion of single elements between the substrate and the layers on the substrate. A diffusion inhibiting layer according to the invention with an adapted aluminum content which lies between the aluminum content of the substrate and the aluminum content of the bonding or corrosion protective layer prevents the diffusion of aluminum and raises therefore the lifespan of the layer system.

1 .- 15 . (canceled) 
     
     
         16 . A layer system, comprising:
 a substrate having a first aluminum content;   a bonding or corrosion protective layer having a second aluminum content arranged over the substrate, wherein the bonding or corrosion protective layer is an alloy of the type MCrAlX;   an outer thermal barrier coating arranged on the bonding or corrosion protective layer; and   a diffusion inhibiting layer arranged between the substrate and the bonding or corrosion protective layer, where the diffusion inhibiting layer contains all the elements of the substrate and where an aluminum content of the diffusion inhibiting layer is between the first and the second aluminum contents wherein:
 a difference of the aluminum content is given between the second aluminum content of the bonding or corrosion protective layer and the first aluminum content of the substrate, and 
 the aluminum content of the diffusion inhibiting layer is between 30% and 70% of the difference added to the first aluminum content, and 
 the composition of the bonding or corrosion protective layer is selected from the group consisting of: group I, group II, group III and group IV, where: 
 group I is (in wt %): 20-22% of chrome, 10.5-11.5% of aluminum, 0.3-0.5% of yttrium, 1.5-2.5% of rhenium, 11-13% of cobalt and balance nickel, 
 group II is (in wt %): 27-29% of chrome, 7-8% of aluminum, 0.5-0.7% of yttrium, 0.3-0.7% of silicon, 29-31% of nickel and balance cobalt, 
 group III is (in wt %): 16-18% of chrome, 12-13% of aluminum, 0.5-0.7% of yttrium, 0.3-0.5% of silicon, 21-23% of cobalt and balance nickel, and 
 group IV is (in wt %): 16-18% of chrome, 9, 5-11% of aluminum, 0.3-0.5% of yttrium, 1-1.8% of rhenium, 24-26% of cobalt and balance nickel. 
   
     
     
         17 . The layer system according to  claim 16 , wherein the substrate is a nickel, cobalt and/or iron based superalloy. 
     
     
         18 . The layer system according to  claim 17 , wherein the alloy of the substrate contains at least nickel, cobalt, chromium and aluminum. 
     
     
         19 . The layer system according to  claim 18 , wherein the composition of the substrate is selected from the group of alloys IN738, IN939 or Rene80. 
     
     
         20 . The layer system according to  claim 19 , wherein the alloy of the substrate further contains at least one of the elements titanium, tantalum, tungsten, niob and/or molybdenum. 
     
     
         21 . The layer system according to  claim 20 , that the aluminum content of the diffusion inhibiting layer is given and
 that the amounts of the other alloy elements of the diffusion inhibiting layer are calculated by:   
       
         
           
             
               
                 
                   
                     Me 
                     i 
                   
                    
                   
                     ( 
                     layer 
                     ) 
                   
                 
                 = 
                 
                   
                     
                       Me 
                       i 
                     
                      
                     
                       ( 
                       substrate 
                       ) 
                     
                   
                   × 
                   
                     ( 
                     
                       1 
                       - 
                       
                         
                           a 
                           * 
                           
                              
                             
                               
                                 Al 
                                 2 
                               
                               - 
                               
                                 Al 
                                 1 
                               
                             
                              
                           
                         
                         
                           
                             ∑ 
                             
                               i 
                               ≠ 
                               Al 
                             
                           
                            
                           
                             
                               Me 
                               i 
                             
                              
                             
                               ( 
                               substrate 
                               ) 
                             
                           
                         
                       
                     
                     ) 
                   
                 
               
               , 
             
           
         
       
       wherein Me i  is the content of at least one of the elements i=Ni, Cr, Co, W, Ta, Ti, Nb, Mo, C, B, Zr and/or Hf. 
     
     
         22 . The layer system according to  claim 21 , wherein a higher amount of aluminum in the diffusion inhibiting layer is only compensated by at least one of the elements nickel, cobalt and/or chromium. 
     
     
         23 . The layer system according to  claim 22 , wherein a higher amount of aluminum in the diffusion inhibiting layer is compensated only by nickel, cobalt and chromium. 
     
     
         24 . The layer system according to  claim 20 , wherein the aluminum content of the diffusion inhibiting layer is given,
 that the amount of at least one alloy element of the elements of the substrate is the same as in the diffusion inhibiting layer and   that the amounts of the other alloy elements (Me i ) of the diffusion inhibiting layer are calculated as:   
       
         
           
             
               
                 
                   Mei 
                    
                   
                     ( 
                     layer 
                     ) 
                   
                 
                 = 
                 
                   
                     
                       Me 
                       i 
                     
                      
                     
                       ( 
                       substrate 
                       ) 
                     
                   
                   × 
                   
                     ( 
                     
                       1 
                       - 
                       
                         
                           a 
                           * 
                           
                              
                             
                               
                                 Al 
                                 2 
                               
                               - 
                               
                                 Al 
                                 1 
                               
                             
                              
                           
                         
                         
                           
                             ∑ 
                             
                               
                                 i 
                                 ≠ 
                                 Al 
                               
                               , 
                               
                                 ≠ 
                                 C 
                               
                             
                           
                            
                           
                             
                               Me 
                               i 
                             
                              
                             
                               ( 
                               substrate 
                               ) 
                             
                           
                         
                       
                     
                     ) 
                   
                 
               
               , 
             
           
         
       
       wherein Me i  is at least one of the elements i=Ni, Cr, Co, W, Ta, Ti, Nb, Mo, C, B, Zr and/or Hf. 
     
     
         25 . The layer system according to  claim 24 , wherein the amount of an element Mec of the group W, Ta, Ti, C, B, Zr, Hf in the diffusion inhibiting layer is the same as the amounts in the substrate. 
     
     
         26 . The layer system according to  claim 25 , wherein the composition of the diffusion inhibiting layer is essentially the composition of the substrate. 
     
     
         27 . The layer system according to  claim 26 , wherein the composition of the diffusion inhibiting layer contains all the elements of the substrate. 
     
     
         28 . The layer system according to  claim 27 , wherein the elements C, B, Zr and/or Hf of the composition of the substrate less than 1 wt % are not present in the diffusion inhibiting layer. 
     
     
         29 . The layer system according to  claim 28 , wherein the layer system is a new made or a refurbished turbine blade or vane, a heat shield element or a casing of a steam or gas turbine.