Oxidation resistant niobium based alloys

Abstract

Oxidation resistant niobium based alloys have a composition to provide a stable ternary phase such as PtYAl or PdYAl, which supplies yttrium and aluminum to the system and forms a protective oxide such as Yttria-Aluminum-Garnet (YAG) scale at elevated temperature. These niobium based alloys further achieve an optimal combination of oxidation resistance and creep strength through a fine dispersion of a coherent second phase. The alloys, withstanding higher combustion temperatures, are useful for extreme-environment propulsion and power applications, including hot sections of gas turbine engines, aerospace turbine blades, and chemical and petroleum plants, where higher turbine efficiency and reduction of operating costs, by-products emissions, and global fuel reserves consumption are desired.

1 . Niobium base alloy, comprising Al, Pt or Pd or a combination thereof, Y, and balance Nb.  
   
   
       2 . The alloy of  claim 1  wherein Al is present in an amount of about 10 to about 25 atomic % of the alloy.  
   
   
       3 . The alloy of  claim 1  wherein Pt or Pd is present in an amount of about 5 to about 40 atomic % of the alloy.  
   
   
       4 . The alloy of  claim 1  wherein Y is present in an amount of about 5 to about 25 atomic %.  
   
   
       5 . The alloy of  claim 1  further comprising an element selected from the group consisting of Cr, Hf, Si, Ti, and W and combination thereof.  
   
   
       6 . The alloy of  claim 1  having PtYAl phase and/or PdYAl phase disposed in a ductile Nb based matrix.  
   
   
       7 . The alloy of  claim 6  where the matrix includes an element to enhance diffusivity ratio of aluminum to oxygen in the matrix.  
   
   
       8 . The alloy of  claim 7  wherein said element is selected from the group consisting of Cr, Hf, Si, Ti, and W and combination thereof.  
   
   
       9 . The alloy of  claim 1  wherein the alloy forms an oxide layer comprising at least one of Al 2 O 3 , Y 2 O 3 , yttrium aluminum garnet, or reaction products of Al 2 O 3  and Y 2 O 3 .  
   
   
       10 . The alloy of  claim 1  comprising Al, Pt, Y, an element selected from the group consisting of Cr, Hf, Si, Ti, and W and combination thereof, and balance Nb and having a ternary phase PtYAl.  
   
   
       11 . The alloy of  claim 1  comprising Al, Pd, Y, an element selected from the group consisting of Cr, Hf, Ti, and W and combination thereof, and balance Nb and having a ternary phase PdYAl.  
   
   
       12 . The alloy of  claim 1  having an oxidation resistance with a target recession rate less than 2.5 μm/hr at 130° C.  
   
   
       13 . The alloy of  claim 1  comprising at least about 53 atomic % niobium, about 13 to about 18 atomic % aluminum, about 2.5 to about 4 atomic % chromium, about 2.5 to about 6 atomic % hafnium, up to about 8 atomic % palladium, up to about 7.45 atomic % platinum, up to about 5 atomic % silicon, about 5 to about 6 atomic % titanium, up to about 2 atomic % tungsten, and about 7 to about 9 atomic % yttrium.  
   
   
       14 . The alloy of  claim 13  which is characterized by target recession rate less than 2.5 μm/hr at 1100° C. or higher.  
   
   
       15 . The alloy of  claim 1  comprising, in atomic percent, about 13 to about 25 parts aluminum, up to about 4 parts chromium, up to about 5 parts hafnium, about 5 to about 15 parts platinum, up to about 5 parts silicon, up to about 6 parts titanium, up to about 2 parts tungsten, about 7 to about 15 parts yttrium, and the balance niobium.  
   
   
       16 . The alloy of  claim 1  comprising, in atomic percent, about 13 to about 23 parts aluminum, up to about 3 parts chromium, up to about 8 parts hafnium, about 5 to about 38 parts palladium, up to about 6 parts titanium, up to about 2 parts tungsten, about 8 to about 25 parts yttrium, and the balance niobium.  
   
   
       17 . The alloy of  claim 1  comprising, in atomic percent, about 13 to about 18 parts aluminum; about 2 to about 4 parts chromium; about 2 to about 5 parts hafnium; about 5 to about 8 parts platinum; up to about 5 parts silicon; about 5 to about 6 parts titanium; up to about 2 parts tungsten; about 7 to about 9 parts yttrium; and the balance niobium.  
   
   
       18 . The alloy of  claim 1  comprising, in atomic percent, about 13 to about 15 parts aluminum; about 2 to about 3 parts chromium; about 2 to about 6 parts hafnium; about 5 to about 8 parts palladium; about 4 to about 6 parts titanium; up to about 2 parts tungsten; about 8 to about 9 parts yttrium; and the balance niobium.  
   
   
       19 . The alloy of  claim 1  comprising the alloy of  claim 15  exposed to air or other oxygen bearing atmosphere at an elevated temperature such that said oxide layer comprising at least one of Al 2 O 3 , Y 2 O 3 , yttrium aluminum garnet, or reaction products of Al 2 O 3  and Y 2 O 3  is present on the component.  
   
   
       20 . A turbine blade or vane made of the alloy of  claim 1 .  
   
   
       21 . The oxidation resistant niobium based alloy of  claim 1  further including a third multicomponent phase as a buffer for excess aluminum.  
   
   
       22 . The alloy of  claim 21  further including an additional, multi-component Nb 2 Al phase as a buffer for excess aluminum in the oxidation resistant niobium based alloy.  
   
   
       23 . Niobium base alloy, comprising a platinum-series element and balance Nb and having a yttrium aluminum garnet layer on the alloy.  
   
   
       24 . The alloy of  claim 23  comprising the platinum-series element selected from Pt or Pd or a combination thereof and an additional element selected from the group consisting of Al, Y, Cr, Hf, Si, Ti, W, and combination thereof.  
   
   
       25 . The alloy of  claim 23  further including a third multicomponent phase as a buffer for excess aluminum.  
   
   
       26 . The alloy of  claim 23  further including an additional, multi-component Nb 2 Al phase as a buffer for excess aluminum in the oxidation resistant niobium based alloy.  
   
   
       27 . A turbine blade or vane comprising the alloy of  claim 23.