Article having a surface protected by a silicon-containing diffusion coating

Abstract

A surface of an article is protected by coating the surface with a silicon-containing coating by preparing a coating mixture of silicon, a halide activator, and an oxide powder, positioning the surface of the article in gaseous communication with the coating mixture, and heating the surface of the article and the coating mixture to a coating temperature of from about 1150° F. to about 1500° F. The article is preferably a component of a gas turbine engine made of a nickel-base superalloy.

1 - 17 . (canceled)  
   
   
       18 . An article comprising 
 a component of a gas turbine engine having a nickel-base superalloy substrate composition; and    a protective layer at a surface of the component, wherein the protective layer comprises a mixture of silicon and elements from the substrate composition interdiffused with the silicon.    
   
   
       19 . The article of  claim 18 , wherein the substrate has a nominal composition, in weight percent, of 13 percent cobalt, 10 percent chromium, 4 percent molybdenum, 3.7 percent titanium, 2.1 percent aluminum, 4 percent tungsten. 0.75 percent niobium, 0.015 percent boron, 0.03 percent zirconium, and 0.03 percent carbon, up to about 0.5 percent iron, balance nickel arid minor amounts of other elements; or has a nominal composition, in weight percent, of about 20.6 percent cobalt, about 13.0 percent chromium, about 3.4 percent aluminum, about 3.7 percent titanium, about 2.4 percent tantalum, about 0.90 percent niobium, about 2.10 percent tungsten, about 3.80 percent molybdenum, about 0.05 percent carbon, about 0.025 percent boron, about 0.05 percent zirconium, up to about 0.5 percent iron, balance nickel and minor amounts of other elements.  
   
   
       20 . The article of  claim 18 , wherein the protective layer consists essentially of a mixture of silicon and elements from the substrate composition interdiffused with the silicon.  
   
   
       21 . (canceled)  
   
   
       22 . The article of  claim 18 , wherein the component is in a cast-and-worked form.  
   
   
       23 . The article of  claim 18 , wherein tile surface of the substrate component is mechanically worked.  
   
   
       24 . (canceled)  
   
   
       25 . The article of  claim 18 , wherein the article is a turbine disk, a seal, or a compressor component.  
   
   
       26 . An article comprising 
 a component of a gas turbine engine having a nickel-base superalloy substrate composition In a cast-and-worked form; and    a protective layer at a surface of the component, wherein the protective layer comprises silicon.    
   
   
       27 . The article of  claim 26 , wherein the substrate has a nominal composition, in weight percent, of 13 percent cobalt, 16 percent chromium, 4 percent molybdenum, 3.7 percent titanium, 2.1 percent aluminum, 4 percent tungsten, 0.75 percent niobium, 0.015 percent boron, 0.03 percent zirconium, and 0.03 percent carbon, up to about 0.5 percent iron, balance nickel and minor amounts of other elements; or has a nominal composition, in weight percent, of about 20.6 percent cobalt, about 13.0 percent chromium, about 3.4 percent aluminum, about 3.7 percent titanium, about 2.4 percent tantalum, about 0.90 percent niobium, about 2.10 percent tungsten, about 3.80 percent molybdenum, about 0.05 percent carbon, about 0.025 percent boron, about 0.05 percent zirconium, up to about 0.5 percent iron, balance nickel and minor amounts of other elements.  
   
   
       28 . The article of  claim 26 , wherein the protective layer comprises a mixture of silicon and elements from the substrate composition interdiffused with the silicon.  
   
   
       29 . (canceled)  
   
   
       30 . The article of  claim 18 , wherein the protective layer is substantially pure silicon at the surface of the component.  
   
   
       31 . The article of  claim 26 , wherein the protective layer is substantially pure silicon at the surface of the component.  
   
   
       32 . An article comprising 
 a component having a nickel-base superalloy substrate composition; and    a protective layer at a surface of the component, wherein the protective layer comprises a mixture of silicon and elements from the substrate composition interdiffused with the silicon, and wherein the protective layer has a gradient composition with a greatest percentage of silicon at the surface of the component and a reduced percentage of silicon with increasing distance into the component from the surface of the component.    
   
   
       33 . The article of  claim 32 , wherein the substrate has a nominal composition, in weight percent, of 13 percent cobalt, 16 percent chromium, 4 percent molybdenum, 3.7 percent titanium, 2.1 percent aluminum, 4 percent tungsten, 0.75 percent niobium, 0.015 percent boron, 0.03 percent zirconium, and 0.03 percent carbon, up to about 0.5 percent iron, balance nickel and minor amounts of other elements; or has a nominal composition, in weight percent, of about 20.6 percent cobalt, about 13.0 percent chromium, about 3.4 percent aluminum, about 3.7 percent titanium, about 2.4 percent tantalum, about 0.90 percent niobium, about 2.10 percent tungsten, about 3.80 percent molybdenum, about 0.05 percent carbon, about 0.025 percent boron, about 0.05 percent zirconium, up to about 0.5 percent iron, balance nickel and minor amounts of other elements.  
   
   
       34 . The article of  claim 32 , wherein the protective layer consists essentially of a mixture of silicon and elements from the substrate composition interdiffused with the silicon.  
   
   
       35 . The article of  claim 32 , wherein the component is in a cast-and-worked form.  
   
   
       36 . The article of  claim 32 , wherein the surface of the component is mechanically worked.  
   
   
       37 . The article of  claim 32 , wherein the article is a turbine disk, a seal, or a compressor component.  
   
   
       38 . The article of  claim 32 , wherein the protective layer is substantially pure silicon at the surface of the component.