Method of adding boron to a heavy metal containing titanium aluminide alloy and a heavy metal containing titanium aluminide alloy

Abstract

A method of adding boron to a tungsten, or tantalum, containing titanium aluminide alloy to form a boride dispersion in the tungsten, or tantalum, containing titanium aluminide. A molten tungsten, or tantalum, containing titanium aluminide alloy is formed and tungsten, or tantalum, boride is added to the molten tungsten, or tantalum, containing titanium aluminide alloy to form a molten mixture. The molten mixture is cooled and solidified to form a tungsten, or tantalum, containing titanium aluminide alloy having a uniform dispersion of tungsten, or tantalum, boride particles substantially without the formation of clusters of tungsten, or tantalum, boride. The titanium aluminide alloy comprises between 0.5 at % and 2.0 at % boron.

We claim:  
     
         1 . A method of adding boron to a heavy metal containing titanium aluminide alloy to form a boride dispersion in the heavy metal containing titanium aluminide, comprising: 
 (a) forming molten heavy metal containing titanium aluminide alloy,    (b) adding heavy metal boride particles to the molten heavy metal containing titanium aluminide alloy to form a molten mixture, the heavy metal boride particles having the same form as undesirable heavy metal boride precipitate clusters,    (c) cooling and solidifying the molten mixture to form a heavy metal containing titanium aluminide alloy having a uniform dispersion of heavy metal boride particles substantially without the formation of heavy metal boride precipitate clusters.    
     
     
         2 . A method as claimed in  claim 1  wherein step (a) comprises forming molten tungsten containing titanium aluminide alloy, 
 (b) adding tungsten boride to the molten tungsten containing titanium aluminide alloy to form a molten mixture, the tungsten boride particles having the same form as undesirable tungsten boride precipitate clusters,  
 (c) cooling and solidifying the molten mixture to form a tungsten containing titanium aluminide alloy having a dispersion of tungsten boride particles substantially without the formation of tungsten boride precipitate clusters.  
 
     
     
         3 . A method as claimed in  claim 1  wherein step (a) comprises forming molten tantalum containing titanium aluminide alloy, 
 (b) adding tantalum boride to the molten tantalum containing titanium aluminide alloy to form a molten mixture, the tantalum boride particles having the same form as undesirable tantalum boride precipitate clusters,  
 (c) cooling and solidifying the molten mixture to form a tantalum containing titanium aluminide alloy having a dispersion of tantalum boride particles substantially without the formation of tantalum boride precipitate clusters.  
 
     
     
         4 . A method as claimed in  claim 1 , wherein the titanium aluminide alloy comprises up to 2.0 at % boron.  
     
     
         5 . A method as claimed in  claim 4  wherein the titanium aluminide alloy comprises up to 1.0 at % boron.  
     
     
         6 . A method as claimed in  claim 1  wherein the titanium aluminide alloy comprises more than 0.5 at % boron.  
     
     
         7 . A method as claimed in  claim 1  wherein the heavy metal boride particles added have a size of 1 to 5 μm.  
     
     
         8 . A method as claimed in  claim 1  wherein the density of heavy metal boride precipitate clusters is up to 3 cm −2 .  
     
     
         9 . A method as claimed in  claim 8  wherein the density of heavy metal boride precipitate clusters is less than 2 cm −2 .  
     
     
         10 . A method as claimed in  claim 1  wherein the heavy metal boride precipitate clusters have a maximum size of 150 μm.  
     
     
         11 . A method as claimed in  claim 1  wherein the heavy metal boride precipitate clusters have a maximum size of 100 μm.  
     
     
         12 . A method as claimed in  claim 1  wherein the titanium aluminide alloy comprises a gamma titanium aluminide.  
     
     
         13 . A method as claimed in  claim 12  wherein the gamma titanium aluminide alloy preferably comprises 44 to 52 at % aluminum, one or more of tungsten and tantalum each in an amount of 0.05 to 8.0 at %, up to 2.0 at % boron and balance titanium plus incidental impurities.  
     
     
         14 . A method as claimed in  claim 13  wherein the gamma titanium aluminide additionally comprises up to 3 at % chromium, up to 6 at % niobium, up to 2 at % manganese.  
     
     
         15 . A method as claimed in  claim 13  wherein the gamma titanium aluminide alloy comprises 45 to 47 at % aluminum, 2 to 6 at % niobium, 0.25 to 2 at % tungsten and the balance titanium plus incidental impurities.  
     
     
         16 . A method as claimed in  claim 15  wherein the gamma titanium aluminide comprises 45 at % aluminum, 5 at % niobium and 1 at % tungsten.  
     
     
         17 . A method as claimed in  claim 16  wherein the gamma titanium aluminide alloy comprises 1 to 2 at % chromium and/or 1 to 2 at % manganese.  
     
     
         18 . A method as claimed in  claim 1  wherein the method comprises forming the titanium aluminide alloy into a turbine blade, a turbine vane, a compressor blade, or a compressor vane.  
     
     
         19 . A method as claimed in  claim 18  wherein the titanium aluminide alloy is cast or forged.  
     
     
         20 . A heavy metal containing titanium aluminide alloy, the titanium aluminide containing heavy metal boride particles substantially without heavy metal boride precipitate clusters, the heavy metal boride particles having the same form as the undesirable heavy metal boride precipitate clusters, and the titanium aluminide alloy comprises up to 2.0 at % boron.  
     
     
         21 . A heavy metal containing titanium aluminide alloy as claimed in  claim 20  wherein the density of the heavy metal boride precipitate clusters is less than 2 cm −2 .  
     
     
         22 . A heavy metal containing titanium aluminide alloy as claimed in  claim 20  wherein the heavy metal boride precipitate clusters have maximum size of 100 μm.  
     
     
         23 . A heavy metal containing titanium aluminide alloy as claimed in  claim 20  wherein the heavy metal is tungsten and the heavy metal boride is tungsten boride.  
     
     
         24 . A heavy metal containing titanium aluminide alloy as claimed in  claim 20  wherein the heavy metal is tantalum and the heavy metal boride is tantalum boride.  
     
     
         25 . A heavy metal containing titanium aluminide alloy as claimed in  claim 20  wherein the titanium aluminide alloy comprises a gamma titanium aluminide.  
     
     
         26 . A heavy metal containing titanium aluminide as claimed in  claim 25  wherein the gamma titanium aluminide alloy preferably comprises 44 to 52 at % aluminum, one or more of tungsten and tantalum each in an amount of 0.05 to 8.0 at %, up to 2.0 at % boron and balance titanium plus incidental impurities.  
     
     
         27 . A heavy metal containing titanium aluminide as claimed in  claim 26  wherein the gamma titanium aluminide additionally comprises up to 3 at % chromium, up to 6 at % niobium, up to 2 at % manganese.  
     
     
         28 . A heavy metal containing titanium aluminide as claimed in  claim 27  wherein the gamma titanium aluminide alloy comprises 45 to 47 at % aluminum, 2 to 6 at % niobium, 0.25 to 2 at % tungsten and the balance titanium plus incidental impurities.  
     
     
         29 . A heavy metal containing titanium aluminide as claimed in  claim 28  wherein the gamma titanium aluminide comprises 45 at % aluminum, 5 at % niobium and 1 at % tungsten.  
     
     
         30 . A heavy metal containing titanium aluminide as claimed in  claim 27  wherein the gamma titanium aluminide alloy comprises 1 to 2 at % chromium and/or 1 to 2 at % manganese.  
     
     
         31 . A heavy metal containing titanium aluminide alloy as claimed in claims  20  wherein the titanium aluminide alloy is in the shape of a turbine blade, a turbine vane, a compressor blade, or a compressor vane.