Braze alloy composition with enhanced oxidation resistance and methods of using the same

Abstract

A cobalt-based braze alloy composition comprises: 22 to 24.75% chromium by weight; 9 to 11% nickel by weight; 6.5 to 7.6% tungsten by weight; 3 to 4% tantalum by weight; 0.55 to 0.65% carbon by weight; 0.3 to 0.6% zirconium by weight; 0.15 to 0.3% titanium by weight; 1.5 to 2.6% boron by weight; 1 to 10% silicon by weight; and cobalt. There are also provided methods of using the same.

1 . A cobalt-based braze alloy composition comprising:
 22 to 24.75% chromium by weight;   9 to 11% nickel by weight;   6.5 to 7.6% tungsten by weight;   3 to 4% tantalum by weight;   0.55 to 0.65% carbon by weight;   0.3 to 0.6% zirconium by weight;   0.15 to 0.3% titanium by weight;   1.5 to 2.6% boron by weight;   1 to 10% silicon by weight; and   cobalt.   
   
   
       2 . The cobalt-based braze alloy composition of  claim 1  further comprising:
 up to 1.3% iron by weight;   up to 0.10% manganese by weight; and   up to 0.02% sulfur by weight.   
   
   
       3 . The cobalt-based braze alloy composition of  claim 1  further comprising:
 2 to 2.6% boron by weight; and   2.5 to 7.5% silicon by weight.   
   
   
       4 . The cobalt-based braze alloy composition of  claim 1  further comprising:
 2.45 to 2.55% boron by weight; and   4 to 6% silicon by weight.   
   
   
       5 . The cobalt-based braze alloy composition of  claim 1  consisting of:
 22 to 24.75% chromium by weight;   9 to 11% nickel by weight;   6.5 to 7.6% tungsten by weight;   3 to 4% tantalum by weight;   0.55 to 0.65% carbon by weight;   0.3 to 0.6% zirconium by weight;   0.15 to 0.3% titanium by weight;   1.5 to 2.6% boron by weight;   1 to 10% silicon by weight;   up to 1.3% iron by weight;   up to 0.10% manganese by weight; and   up to 0.02% sulfur by weight; and   cobalt.   
   
   
       6 . A method of repairing or reconstructing a superalloy component comprising the steps of:
 forming a presintered preform by mixing a hardface alloy powder with a cobalt-based braze alloy composition comprising 22 to 24.75% chromium by weight, 9 to 11% nickel by weight, 6.5 to 7.6% tungsten by weight, 3 to 4% tantalum by weight, 0.55 to 0.65% carbon by weight, 0.3 to 0.6% zirconium by weight, 0.15 to 0.3% titanium by weight, 1.5 to 2.6% boron by weight, 1 to 10% silicon by weight, and cobalt; wherein the presintered preform comprises 60-90% hardface alloy powder by weight and 10-40% cobalt-based braze alloy composition by weight;   sintering the presintered preform to make a sintered component;   shaping the sintered component;   welding the sintered component to the superalloy component to form a combination; and   subjecting the combination to a heat treatment cycle.   
   
   
       7 . The method of  claim 6 , wherein the heat treatment cycle comprises a heating cycle sub-step and a cooling cycle sub-step. 
   
   
       8 . The method of  claim 6 , wherein the superalloy component comprises a component of a gas turbine. 
   
   
       9 . The method of  claim 6 , wherein the superalloy component is a bucket angel wing or a bucket tip. 
   
   
       10 . The method of  claim 6 , wherein the heat treatment cycle comprises the steps of: heating a furnace to 650° C. at a rate of 14° C./minute; maintaining a temperature of 650° C. for 30 minutes; heating the furnace to 980° C. at a rate of 14° C./minute; maintaining a temperature of 980° C. for 30 minutes; heating the furnace to 1204 to 1218° C. at a rate of 19° C./minute; maintaining a temperature of 1204 to 1218° C. for 20 minutes; cooling the furnace to a temperature of 1120° C.; maintaining a temperature of 1120° C. for 30 minutes; and cooling the furnace to a temperature of 815° C.