Methods for improving braze joints utilizing gold/copper/nickel brazing alloys

Abstract

A method to improve the impact resistance of a braze joint between a tungsten/carbide/cobalt substrate and a substrate including titanium or alloy thereof includes utilizing a brazing material including gold, nickel, and copper present in respective amounts to improve the ductility of the braze joint.

1 . A method of improving the impact resistance of a braze joint between a midspan shroud of a fan or compressor blade for a gas turbine engine and a wear pad brazed thereto, the method comprising:
 brazing the wear pad to the midspan shroud with a brazing material including:
 about 40 to about 60 wt % gold; 
 about 5 to about 16 wt % nickel; 
 about 35 to about 55 wt % copper; 
   
       wherein the gold, nickel, and copper are present in respective amounts to provide the brazing material with a post-braze hardness of between about 450 and about 600 KHN, and the braze joint with an impact resistance of greater than about 0.60 Joules. 
     
     
         2 . The method according to  claim 1  further comprising:
 providing the midspan shroud, wherein the midspan shroud includes a face for receiving the wear pad;   providing the wear pad; and   disposing the brazing material between the wear pad and the face to provide a brazing assembly.   
     
     
         3 . The method according to  claim 2  wherein the brazing material is in a form selected from a homogeneous alloy form, a powder form, or a layered form. 
     
     
         4 . The method according to  claim 3  wherein the brazing material is in the layered form, and wherein the method includes:
 positioning a layer consisting essentially of a copper foil between a layer of nickel-containing foil and a layer of gold-containing foil.   
     
     
         5 . The method according to  claim 2  wherein providing the midspan shroud includes:
 providing a midspan shroud requiring repair due to a damaged wear pad; and   removing the damaged wear pad.   
     
     
         6 . The method according to  claim 5  wherein the damaged wear pad is removed chemically, mechanically, or a combination of chemically and mechanically. 
     
     
         7 . The method according to  claim 2  further comprising:
 subjecting the brazing assembly to an induction heating process for a duration of at least about 1 minute and less than 10 minutes at braze temperatures of less than about 1900° F. (about 1038° C.).