Intermediate strength alloys for high temperature service in liquid-salt cooled energy systems
An alloy consists essentially of, in terms of weight percent: 6 to 8.5 Cr, 5.5 to 13.5 Mo, 0.4 to 7.5 W, 1 to 2 Ti, 0.7 to 0.85 Mn, 0.05 to 0.3 Al, up to to 0.1 Co, 0.08 to 0.5 C, 1 to 5 Ta, 1 to 4 Nab, 1 to 3 Hf, balance Ni. The alloy is characterized by, at 850° C., a yield strength of at least 36 Ksi, a tensile strength of at least 40 Ksi, a creep rupture life at 12 Ksi of at least 72.1 hours, and a corrosion rate, expressed in weight loss [g/(cm2sec)]×10 −11 during a 1000 hour immersion in liquid FLiNaK at 850° C., in the range of 8 to 25.
1. An alloy for use in components in contact with liquid fluorides, consisting essentially of, in terms of weight percent:
Cr: 6 to 8.5,
Mo: 5.5 to 13.5,
W: 0.4 to 7.5,
Ti: 1 to 2,
Mn: 0.7 to 0.85,
Al: 0.05 to 0.3,
Co: 0 to 0.1,
C: 0.08 to 0.5,
Ta: 1 to 5,
Nb: 1 to 4,
Hf: 1 to 3,
Fe: ≦0.01,
Ni: balance,
with Al+Ti≦2.3 wt. %;
and said alloy being characterized by
i) at alloy temperatures of 850° C., a yield strength of at least 36 Ksi, a tensile strength of at least 40 Ksi, a creep rupture life at 12 Ksi of at least 72.1 hours, and a corrosion rate of 8×10 −11 g/cm 2 s to 25×10 −11 g/cm 2 s of weight loss during a 1000 hour immersion in liquid FLiNaK at 850° C.;
ii) at alloy temperatures of 850° C., a matrix consisting of γ and 4.0 to 10 wt. % total precipitates, said total precipitates consisting of at least one M 6 C type carbide and at least one additional precipitate selected from the group consisting of MC type carbides and Ni 5 M type precipitates;
iii) said alloy possessing an Mo Equivalent of no less than 5, wherein,
Mo
Equivalent
=
%
Mo
+
1.15
×
183.84
95.95
×
%
W
and iv) said alloy having a corrosion susceptibility index, CSI, of no less than about 0.1 and no more than about 0.2, wherein
CSI
=
%
Al
+
%
Cr
+
%
Ti
+
%
Nb
+
%
Hf
+
%
Ta
%
Ni
+
%
Fe
+
%
Co
+
%
Mn
+
%
Mo
+
%
W
+
%
Re
+
%
Ru
.
2. An alloy in accordance with claim 1 wherein the range of Cr is 6.7 to 8.3 weight percent.
3. An alloy in accordance with claim 1 wherein the range of Mo is 5.81 to 12.93 weight percent.
4. An alloy in accordance with claim 1 wherein the range of W is 0.52 to 6.99 weight percent.
5. An alloy in accordance with claim 1 wherein the range of Ti is 1.15 to 1.22 weight percent.
6. An alloy in accordance with claim 1 wherein the range of Mn is 0.75 to 0.79 weight percent.
7. An alloy in accordance with claim 1 wherein the range of Al is 0.08 to 0.11 weight percent.
8. An alloy in accordance with claim 1 wherein the range of Co is 0.01 to 0.08 weight percent.
9. An alloy in accordance with claim 1 wherein the range of Ta is 1.18 to 4.82 weight percent.
10. An alloy in accordance with claim 1 wherein the range of Nb is 1.06 to 3.76 weight percent.
11. An alloy in accordance with claim 1 wherein the range of Hf is 1.13 to 2.77 weight percent.
12. An alloy in accordance with claim 1 wherein the range of C is 0.1 to 0.25 weight percent.
13. An alloy in accordance with claim 1 wherein sad alloy is further characterized by 1 to 8 wt. % M 6 C type carbides.
14. An alloy in accordance with claim 1 wherein said alloy is further characterized by up to 3.5 wt. % MC type carbides.
15. An alloy in accordance with claim 1 wherein said alloy is further characterized by up to 3 wt. % Ni 5 M type precipitates.