Gamma - gamma prime strengthened tungsten free cobalt-based superalloy

Abstract

Embodiments herein present the invention of a class of Tungsten (W) free Cobalt based (γ-γ′) superalloys with the basic chemical composition comprising in % by weight: 0.5 to 10 Aluminium (Al) and 1 to 15 Molybdenum (Mo) with at least one or both of 0.5 to 12 Niobium (Nb) and 0.5 to 12 Tantalum (Ta), with the remainder being Cobalt (Co). Some part of the cobalt can be replaced by nickel (50% or less). In Nickel added alloys, some part of either cobalt of nickel can be replaced by at least one among the transition metal selected from the group consisting of 10% or less Iridium, 10% or less Platinum, 10% or less Palladium, 15% or less Chromium and combination thereof. Again in nickel added alloys, further addition of at least one among the transition metals zirconium (5% or less), hafnium (5% or less), vanadium (5% or less), titanium (5% or less), and yttrium (5% or less), boron (2% or less), carbon (2% or less), rhenium (10% or less), ruthenium (5% or less) for further fine tune the solvus temperature, volume fraction of γ′ and creep properties.

1 . A Tungsten (W) free Cobalt based (γ-γ′) superalloy composition with high strength and ductility comprising, in weight percentage,
 i) 0.5 to 10% Aluminium (Al); 
 ii) 1 to 15% Molybdenum (Mo); 
 iii) one or both of 0.5 to 12 Niobium (Nb) and/or 0.5 to 12 Tantalum (Ta); 
 iv) remainder Cobalt (Co) and unavoidable impurities. 
 
     
     
         2 . The Cobalt based (γ-γ′) superalloy by composition of  claim 1 , wherein a part of the weight percentage of Cobalt is replaced by 50% or less Nickel. 
     
     
         3 . The Cobalt based (γ-γ′) superalloy composition of  claim 2 , wherein a part of the weight percentage of Cobalt is replaced by at least one transition metal selected from the group consisting of 10% or less Iridium, 10% or less Platinum, 10% or less Palladium, 15% or less Chromium and combinations thereof. 
     
     
         4 . The Cobalt based (γ-γ′) superalloy composition of  claim 2 , wherein a part of the weight percentage of Nickel is replaced by at least one transition metal selected from the group consisting of 50% or less Iridium, 10% or less Platinum, 10% or less Palladium, 15% or less Chromium and combinations thereof. 
     
     
         5 . The Cobalt based (γ-γ′) superalloy composition of  claim 2 , further comprising at least one transition metal selected from the group consisting of 5% or less Titanium, 5% or less Vanadium, 5% or less Hafnium, 5% or less Zirconium, 5% or less Yttrium, 2% or less Boron, 2% or less Carbon, 10% or less Rhenium, 5% or less Ruthenium and combinations thereof. 
     
     
         6 . The Cobalt based (γ-γ′) superalloy composition of  claim 1 , wherein no other phase except γ-γ′ is present. 
     
     
         7 . A process of producing Tungsten (W) free γ-γ′ cobalt based superalloy with high strength and ductility comprising the steps of:
 a. Melting constituents of the composition of any of the claims from  1  to  5  to form a molten material; 
 b. Casting the molten material into a desirable mold to form a cast alloy; 
 c. Optionally the cast alloy can be mechanically worked like forging, rolling or related processes to produce wrought product, 
 d. Homogenizing and solutionizing the alloy at a higher temperature to form a solutionized alloy; 
 e. Cooling of the solutionized alloy; 
 f. Aging of the solutionized alloy at a temperature ranging from 500° C. to 1100° C. to form an aged alloy; and 
 g. Cooling of the aged alloy to form the γ-γ′ cobalt based superalloy with high strength and ductility. 
 
     
     
         8 . The process of  claim 7 , wherein the cooling of the solutionized or the aged alloy is done by furnace cooling or air cooling or water quenching. 
     
     
         9 . The process of  claim 7 , wherein the alloy is solutionized at the temperature ranging from 1100° C. to 1400° C. for time between 1 to 20 hours.