High strength alloys for high temperature service in liquid-salt cooled energy systems
An essentially cobalt-free alloy consists essentially of, in terms of weight percent: 6.3 to 7.2 Cr, 0.5 to 2 Al, 0 to 5 Fe, 0.7 to 0.8 Mn, 9 to 12.5 Mo, 0 to 6 Ta, 0.75 to 3.5 Ti, 0.01 to 0.25 Nb, 0.2 to 0.6 W, 0.02 to 0.04 C, 0 to 0.001 B, 0.0001 to 0.002 N, balance Ni. The alloy is characterized by a γ′ microstructural component in the range of 3 to 17.6 weight percent of the total composition. The alloy is further characterized by, at 850° C., a yield strength of at least 60 Ksi, a tensile strength of at least 70 Ksi, a creep rupture life at 12 Ksi of at least 700 hours, and a corrosion rate, expressed in weight loss [g/(cm 2 sec)]10 −11 during a 1000 hour immersion in liquid FLiNaK at 850° C., in the range of 5.5 to 17.
1. A cobalt-free Υ′-strengthened alloy consisting essentially of, expressed in weight percent of the total composition:
Cr 6.3 to 7.2
Al 0.5 to 2
Fe 0 to 5
Mn 0.7 to 0.8
Mo 9 to 12.5
Ta 0 to 6
Ti 0.99 to 3.5
Nb 0.01 to 0.25
W 0.2 to 0.6
C 0.02 to 0.04
B 0 to 0.0005
N 0.0001 to 0.002
Ni balance said alloy having a Υ′ microstructural component in an amount of calculated weight percent of at least 3 and no more than 17.6; and said alloy being characterized by, at 850° C., a yield strength of at least 60 Ksi, a tensile strength of at least 70 Ksi, and a creep rupture life at 12 Ksi of at least 700 hours, and a corrosion rate, expressed in weight loss [g/(cm 2 sec)]10 −11 during a 1000 hour immersion in liquid FLiNaK at 850° C., in the range of 5.5 to 17, and further characterized by a corrosion susceptibility index of no less than about 0.14 and no more than about 0.2.
2. An alloy in accordance with claim 1 wherein the range of Al is 0.75 to 2weight percent.
3. An alloy in accordance with claim 1 wherein the range of Fe is 0 to 0.05weight percent.
4. An alloy in accordance with claim 1 wherein said Υ′ microstructural component in an amount of a calculated weight percent of at least 3 and no more than 11.8.
5. An alloy in accordance with claim 4 wherein said Υ′ microstructural component in an amount of a calculated weight percent of at least 3 and no more than 9.4.
6. An alloy in accordance with claim 1 wherein said yield strength is at least 65 Ksi.
7. An alloy in accordance with claim 1 wherein said tensile strength is at least 75 Ksi.
8. An alloy in accordance with claim 1 wherein said creep rupture life is at least 750hours.
9. An alloy in accordance with claim 1 wherein said corrosion rate is no more than 8.4.