Alloy with ion bombarded surface for environmental protection

Abstract

An article may include a substrate that comprises a nickel alloy. The substrate may include a modified subsurface region and a bulk region. The modified subsurface region may include a first composition and the bulk region may include a second composition different than the first composition. The modified subsurface region may include at least one of a reactive element or a noble metal, and the modified subsurface region comprises a thickness of less than about 0.3 μm measured in a direction substantially normal to a surface of the substrate. The modified subsurface region may be formed by depositing a layer including at least one of the reactive element or the noble metal in a layer on a surface of the substrate and introducing the at least one of the reactive element or the noble metal into the modified subsurface region using ion bombardment.

1 . A method comprising:
 depositing a plurality of atoms in a layer on a surface of a substrate that comprises a nickel alloy, wherein the plurality of atoms comprises at least one of a reactive element or a noble metal, and wherein the nickel alloy comprises a microstructure; and   bombarding the layer with inert ions to implant at least some of the plurality of atoms in the substrate and form a modified subsurface region with a maximum depth of less than about 0.3 μm measured in a direction substantially normal to the surface, wherein the microstructure is substantially unaffected by the formation of the modified subsurface region.   
     
     
         2 . The method of  claim 1 , wherein the inert ions comprise at least one of Xe, He, Ne, Ar, Kr, or Rn. 
     
     
         3 . The method of  claim 1 , wherein the plurality of atoms comprises the reactive element, and wherein the reactive element comprises at least one of Y, La, Hf, Zr, Ce, Si, or Cr. 
     
     
         4 . The method of  claim 1 , wherein the plurality of atoms comprises the noble metal, and wherein the noble metal comprises at least one of Ru, Rh, Pd, Pt, Os, Ir, Ag, or Au. 
     
     
         5 . The method of  claim 1 , wherein the plurality of atoms consist essentially of a single element selected from the group consisting of the reactive element or the noble metal. 
     
     
         6 . The method of  claim 1 , wherein the modified subsurface region of the substrate comprises a γ-Ni+γ′-Ni 3 Al phase constitution prior to bombarding the layer with inert ions, and wherein bombarding the layer with inert ions leaves the γ-Ni+γ′-Ni 3 Al phase constitution in the modified subsurface region of the substrate substantially unchanged. 
     
     
         7 . The method of  claim 1 , wherein the plurality of atoms comprises the reactive element, wherein the reactive element comprises at least one rare earth reactive element, and wherein the modified subsurface region comprises less than about 1 wt. % of the at least one rare earth reactive element. 
     
     
         8 . The method of  claim 1 , wherein the plurality of atoms comprises the reactive element, wherein the reactive element comprises Si, and wherein the modified subsurface region comprises less than about 2 wt. % Si. 
     
     
         9 . The method of  claim 1 , wherein the plurality of atoms comprises the reactive element, wherein the reactive element comprises Cr, and wherein the modified subsurface region comprises less than about 30 wt. % Cr. 
     
     
         10 . The method of  claim 1 , wherein the plurality of atoms comprise the noble metal, and wherein the modified subsurface region comprises less than about 20 wt. % of the noble metal. 
     
     
         11 . The method of  claim 1 , wherein the superalloy substrate comprises a γ-Ni+γ′-Ni 3 Al phase constitution, further comprising:
 prior to depositing the plurality of atoms in the layer on the surface of the substrate that comprises the nickel alloy, heat treating the substrate at a temperature between 41.67° C. and 83.33° C. below a γ′-Ni 3 Al solvus temperature of the alloy to dissolve substantially all tertiary γ′-Ni 3 Al present in the subsurface region, so that the subsurface region is essentially free of tertiary γ′-Ni 3 Al. 
 
     
     
         12 . The method of  claim 1 , further comprising:
 heat treating the substrate including the subsurface region to oxidize Cr or Al present in the subsurface region to form an oxide scale on a surface of the subsurface region.   
     
     
         13 . An article comprising a substrate comprising a nickel alloy, wherein the substrate comprises a modified subsurface region and a bulk region, wherein the modified subsurface region comprises a first composition and the bulk region comprises a second composition different than the first composition, wherein the modified subsurface region comprises at least one of a reactive element or a noble metal, and wherein the modified subsurface region defines a maximum thickness of less than about 0.3 μm measured in a direction substantially normal to a surface of the substrate, and wherein a microstructure of the modified subsurface region is substantially the same as the microstructure of the bulk region adjacent to the modified subsurface region. 
     
     
         14 . The article of  claim 13 , wherein the modified subsurface region comprises a γ-Ni+γ′-Ni 3 Al phase constitution. 
     
     
         15 . The article of  claim 13 , wherein the modified subsurface region comprises the reactive element, wherein the reactive element comprises at least one of Y, La, Hf, Zr, or Ce, and wherein the modified subsurface region comprises less than about 1 wt. % of the at least one of Y, La, Hf, Zr, or Ce. 
     
     
         16 . The article of  claim 13 , wherein the modified subsurface region comprises the reactive element, wherein the reactive element comprises Si, and wherein the modified subsurface region comprises less than about 2 wt. % Si. 
     
     
         17 . The article of  claim 13 , wherein the modified subsurface region comprises the reactive element, wherein the reactive element comprises Cr, and wherein the modified subsurface region comprises less than about 30 wt. % Cr. 
     
     
         18 . The article of  claim 13 , wherein the modified subsurface region comprises the noble metal, and wherein the subsurface region comprises less than about 20 wt. % of the noble metal. 
     
     
         19 . The article of  claim 18 , wherein the noble metal comprises at least one of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au. 
     
     
         20 . The article of  claim 13 , further comprising an oxide scale formed on a surface of the modified subsurface region, wherein the oxide scale comprises at least one of chromium oxide (Cr 2 O 3 ) or aluminum oxide (Al 2 O 3 ).