Nickel-base superalloy having an optimized platinum-aluminide coating

Abstract

A nickel-base superalloy substrate includes a surface region having an integrated aluminum content of from about 18 to about 24 percent by weight and an integrated platinum content of from about 18 to about 45 percent by weight, with the balance components of the substrate. The substrate is preferably a single-crystal advanced superalloy selected for use at high temperatures. The substrate may optionally have a ceramic layer deposited over the platinum-aluminide region, to produce a thermal barrier coating system. The platinum-aluminide region is produced by diffusing platinum into the substrate surface, and thereafter diffusing aluminum into the substrate surface.

1 - 7 . (canceled)  
   
   
       8 . A method for preparing an article having a platinum-aluminide surface region, comprising the steps of: 
 providing a substrate having a nickel-base superalloy substrate bulk composition and a substrate surface;    depositing a layer of platinum upon the substrate surface, thereafter;    diffusing a platinum from the layer of platinum into the substrate surfaces thereafter;    providing a source of aluminum; and thereafter    diffusing aluminum from the source of aluminum into the substrate surface for a time sufficient to produce a substantially single phase surface region at the substrate surface, the surface region having an integrated aluminum content of from about 18 to about 24 percent by weight and an integrated platinum content of from about 18 to about 45 percent by weight, balance components of the substrate bulk composition, wherein the surface region comprises a surface, distant from the substrate surface, and which surface region includes aluminum content and platinum content which is relatively high adjacent to the surface and decreases with increasing depth into the surface region and the substrate.    
   
   
       9 . The method of  claim 8 , including an additional step, after the step of diffusing aluminum, of 
 depositing a ceramic layer overlying the substrate surface.    
   
   
       10 . The method of  claim 8 , including an additional step, after the step of diffusing aluminum, of 
 annealing the substrate and the surface region.    
   
   
       11 . The method of  claim 8 , wherein the step of diffusing aluminum includes the step of 
 diffusing aluminum from the source of aluminum into the substrate surface for a time sufficient that the surface region has an integrated aluminum content of from about 21 to about 23 percent by weight and an integrated platinum content of from about 30 to about 45 percent by weight, balance components of the substrate bulk composition.    
   
   
       12 . The method of  claim 8 , wherein the step of providing a substrate includes the step of 
 providing a nickel-base superalloy substrate which is substantially a single crystal and has a composition that includes from about 5 to about 16 weight percent aluminum and from a bout 1 to about 8 weight percent rhenium.    
   
   
       13 . The method of  claim 8 , wherein the step of providing a substrate includes the step of 
 providing a nickel-base superalloy substrate which is substantially a single crystal and has a composition selected from the group consisting of (a) 7.5 percent cobalt, 7 percent chromium, 6.2 percent aluminum, 6.5 percent tantalum, 5 percent tungsten, 1.5 percent molybdenum, 3 percent rhenium, balance nickel; (b) 12.5 percent cobalt, 4.5 percent chromium, 6 percent aluminum, 7.5 percent tantalum, 5.8 percent tungsten, 1.1 percent molybdenum, 5.4 percent rhenium, 0.15 percent hafnium, balance nickel; and (c) 12 percent cobalt, 6.8 percent chromium, 6.2 percent aluminum, 6.4 percent tantalum, 4.9 percent tungsten, 1.5 percent molybdenum, 2.8 percent rhenium, 1.5 percent hafnium, balance nickel.    
   
   
       14 - 20 . (canceled)  
   
   
       21 . A method of forming a thermal barrier coating on a substrate, comprising: 
 chemical vapor depositing a substantially single phase diffusion aluminide layer on the substrate which includes a nickel base superalloy substrate, said aluminide layer including an average aluminum concentration in the range of about 18 to about 24% by weight and an average platinum concentration in the range of about 8 to about 45% by weight, wherein said aluminide layer further comprises a surface, and includes the aluminum content and the platinum content which is relatively high adjacent to the surface and decreases with increasing depth into the aluminide layer and the substrate; and    depositing a ceramic thermal barrier layer on the aluminide layer.    
   
   
       22 . The method of  claim 21  wherein the aluminide layer comprises an average platinum concentration of about 18 to about 45% by weight.