Porous ceramic layer system

Abstract

A porous ceramic layer system is provided having two layers of porous layers with a tightly controlled and matched porosity. The layer system has a substrate, a metallic bonding layer on the substrate, an inner ceramic layer having a porosity, an outer ceramic layer on the inner ceramic layer, with a two-layered NiCoCrAlX layer as the metallic bonding layer, with a lower NiCoCrAlY layer, in which the content of chromium (Cr) in the lower NiCoCrAlY layer is less than the content of chromium (Cr) in the outer NiCoCrAlY layer.

1 - 18 . (canceled) 
     
     
         19 . A layer system at least comprising:
 a substrate,   a metallic bonding layer on the substrate,   an inner ceramic layer having a porosity, in % by volume, of 8% to <15% on the bonding layer,   and an outer ceramic layer, having a porosity of >15% to 22%, on the inner ceramic layer,   a two-layered NiCoCrAlX layer as the metallic bonding layer,   with a lower NiCoCrAlY layer, in which the content of chromium (Cr) in the lower NiCoCrAlY layer is at least 3% by weight less than the content of chromium (Cr) in an outer NiCoCrAlY layer.   
     
     
         20 . The layer system as claimed in  claim 19 ,
 wherein the material of the lower ceramic layer comprises zirconium oxide.   
     
     
         21 . The layer system as claimed in  claim 19 ,
 wherein the outer ceramic layer comprises zirconium oxide.   
     
     
         22 . The layer system as claimed in  claim 19 ,
 wherein the substrate comprises a nickel-based or cobalt-based superalloy.   
     
     
         23 . The layer system as claimed in  claim 19 ,
 wherein the material of the ceramic layers is different.   
     
     
         24 . The layer system as claimed in  claim 19 ,
 wherein the inner ceramic layer has a form which is at least 10% thinner than the outer ceramic layer.   
     
     
         25 . The layer system as claimed in  claim 19 ,
 wherein the layer system consists of:
 the substrate, 
 the two-layered metallic bonding layer, 
 the inner ceramic layer, and 
 the outer ceramic layer. 
   
     
     
         26 . The layer system as claimed in  claim 19 ,
 wherein the content of cobalt (Co) in the lower NiCoCrAlY layer is the same as or comparable with the content of cobalt (Co) in the outer NiCoCrAlY layer.   
     
     
         27 . The layer system as claimed in  claim 19 ,
 wherein the difference in the content of chromium (Cr) in the metallic layers is 3% by weight to 13% by weight.   
     
     
         28 . The layer system as claimed in  claim 19 ,
 wherein the content of aluminum (Al) in the lower NiCoCrAlY layer is the same as or comparable with the content of aluminum (Al) in the outer NiCoCrAlY layer.   
     
     
         29 . The layer system as claimed in  claim 19 ,
 wherein the content of yttrium (Y) in the lower NiCoCrAlY layer is the same as or comparable with the content of yttrium (Y) in the outer NiCoCrAlY layer.   
     
     
         30 . The layer system as claimed in  claim 19 ,
 wherein the lower NiCoCrAlY layer has the following composition in % by weight:
 cobalt (Co): 24%-26%, 
 chromium (Cr): 11%-15%, 
 aluminum (Al): 10.0%-12.0%, 
 yttrium (Y): 0.2%-0.6%, 
 nickel. 
   
     
     
         31 . The layer system as claimed in  claim 19 ,
 wherein the upper NiCoCrAlY layer has the following composition in % by weight:
 cobalt (Co): 24%-26%, 
 chromium (Cr): 23%-25%, 
 aluminum (Al): 9%-12.0%, 
 yttrium (Y): 0.2%-0.6%, 
 nickel. 
   
     
     
         32 . The layer system as claimed in  claim 19 ,
 which has no gradients in the content of chromium (Cr) in the layer.   
     
     
         33 . The layer system as claimed in  claim 19 ,
 wherein a thermally grown oxide layer is formed or is present on the outer NiCoCrAlY layer.   
     
     
         34 . The layer system as claimed in  claim 19 ,
 wherein the metallic bonding layer has a total thickness of 180 μm to 300 μm.   
     
     
         35 . The layer system as claimed in  claim 19 ,
 wherein the powder used for the upper NiCoCrAlY layer is coarser than the grain size of the powder for the lower NiCoCrAlY layer, such that the upper layer comprises larger grains than the lower layer.   
     
     
         36 . The layer system as claimed in  claim 19 ,
 which comprises no rhenium (Re) in the metallic layers.