NiCrCoMoW Age Hardenable Alloy for Creep-Resistant High Temperature Applications, and Methods of Making

Abstract

The invention provides a Ni-based superalloy with good yield stress and ultimate tensile strength and good creep strength (long creep life at high temperature). Methods of making the alloy are also described.

What is claimed: 
     
         1 . A nickel alloy, comprising: 18.5 to 20.5% Cr; 9.0 to 11.0% Co; 4.0 to 5.0% Mo; 3.25 to 4.25% W; 2.3 to 2.7% Ti; 1.5 to 1.9% Al; 0 to 0.1% C; 0 to 0.02% B; up to 1.5% Fe, 0.5% or less of Mn, Si, P, Cu or other transition metals; the balance Ni and impurities. 
     
     
         2 . The alloy of  claim 1 , comprising: 18.5 to 20.5% Cr; 9.0 to 11.0% Co; 4.0 to 5.0% Mo; 3.25 to 4.25% W; 2.3 to 2.7% Ti; 1.5 to 1.9% Al; 0.003 to 0.01% B; 0.0 to 1.5% Fe; 0.04 to 0.08% C; 0 to 0.3% Mn; 0 to 0.15% Si; 0 to 0.15% P; 0 to 0.01% Cu; the balance Ni and impurities. 
     
     
         3 . The alloy of  claim 1  comprising M 23 C 6  carbides at grain boundaries in the alloy. 
     
     
         4 . The alloy of  claim 1  comprising γ′ (or γ″ or γ′/γ″) precipitates distributed within a y grain. 
     
     
         5 . The alloy of  claim 1  characterizable by a time to failure at 760° C. and 259 MPa of at least 4000 h, or at least 5000 h, or at least 6000 h, or at least 7000 h, or in the range of 4000 to 8000 h or in the range of 4500 to 7500 h. 
     
     
         6 . The alloy of  claim 2  characterizable by a time to failure at 800° C. and 155 MPa of at 20 least 3000 h, or at least 4000 h, or at least 5000 h, or at least 6,000 h, or in the range of 3000 to 7000 h or in the range of 4000 to 6500 h. 
     
     
         7 . A method of heat treating a nickel alloy comprising Cr and Co, comprising the sequential steps of treating the nickel alloy:
 1100±25° C. for 0.5 to 5 h;   1160±25° C. for 1.5 to 10 h; and 1200±25° C. for 2 to 20 h.   
     
     
         8 . The method of  claim 7  wherein the nickel alloy comprises the alloy of  claim 1 . 
     
     
         9 . The method of  claim 7  further comprising a heat treatment comprising heating at 1165±25° C. for 400±100 sec and aging steps of 1010±20° C. for 0.5 to 10 h and then 788±15° C. for 2 to 15 h. 
     
     
         10 . The method of  claim 7  further comprising a heat treatment comprising heating at 1165±25° C. for 400±100 sec and aging steps of 1060±20° C. for 0.5 to 10 h and then 800±15° C. for 2 to 15 h. 
     
     
         11 . The method of  claim 7  further comprising a heat treatment comprising heating at 1165±25° C. for 400±100 sec and an aging step of 800±15° C. for 2 to 15 h. 
     
     
         12 . The method of  claim 7  wherein, relative to HAYNES® 282® alloy, the treatments increase life of the alloy in creep at 760° C. and 259 MPa by at least 70%, or at least 100%, or in the range of 80 to 150%, 90 to 140% or 80 to 130%. 
     
     
         13 . The method of  claim 7  wherein the treatments increase the elongation to failure of the alloy in creep at 780° C. and 207 MPa by at least 40%, or at least 60%, or in the range of 40 to 100%, 50 to 90% or 40 to 80%. 
     
     
         14 . A nickel alloy, comprising: 18.5 to 20.5% Cr; 9.0 to 11.0% Co; greater than 50% Ni and characterizable by one or any combination of the following properties:
 a time to failure at 760° C. and 259 MPa of at least 4000 h, or at least 5000 h, or at least 6000 h, or at least 7000 h, or in the range of 4000 to 8000 h or in the range of 4500 to 7500h; and   a time to failure at 800° C. and 155 MPa of at least 3000 h, or at least 4000 h, or at least 5000 h, or at least 6000 h, or in the range of 3000 to 7000 h or in the range of 4000 to 6500 h.   
     
     
         15 . The alloy of  claim 14  comprising γ′ (or γ″ or γ′/γ″) precipitates distributed within a y matrix grain interior. 
     
     
         16 . The alloy of  claim 14  characterizable by a time to failure at 760° C. and 259 MPa of at least 6000 h. 
     
     
         17 . The alloy of  claim 14  characterizable by a time to failure at 800° C. and 155 MPa of at least 4000 h. 5 18. A nickel alloy, comprising: 18.5 to 20.5% Cr; 9.0 to 11.0% Co; greater than 50% Ni and characterizable by one or any combination of the following properties:
 a time to failure at 800° C. and 259 MPa of at least 700 h, or at least 800 h, or at least 900 h, or at least 1000 h, or in the range of 700 to 2000 h or in the range of 900 to 1500 h; and 
 a time to failure at 840° C. and 155 MPa of at least 1200 h, or at least 1400 h, or at least 1600 h, or at least 1800 h, or in the range of 1200 to 2200 h or in the range of 1600 to 2000 h. 
 
     
     
         19 . The alloy of claim  18  comprising γ′ (or γ″ or γ′/γ″) precipitates distributed within a γ matrix grain interior.