Intermediate Strength Alloys for High Temperature Service in Liquid-Salt Cooled Energy Systems

• US 20150197832A1
• Filed: 01/10/2014
• Published: 07/16/2015
• Est. Priority Date: 01/10/2014
• Status: Active Grant

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Muralidharan, Govindarajan, Holcomb, David Eugene, Wilson, Dane Francis
• Granted Patent: US 9,683,280 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C22C 19/057 with the maximum Cr content being less 10%

Abstract

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 Nb, 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.

Claims

1. An alloy 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 <

0.005 to 0.1

C 0.08 to 0.5

Ta 1 to 5

Nb 1 to 4

Hf 1 to 3

Ni balance

said alloy being 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<sup>−

11</sup> during a 1000 hour immersion in liquid FLiNaK at 850°

C., in the range of 8 to 25.

2. An alloy in accordance with claim 1 wherein said alloy is essentially Fe free.

3. An alloy in accordance with claim 1 wherein the range of Cr is 6.7 to 8.3 weight percent.

4. An alloy in accordance with claim 1 wherein the range of Mo is 5.81 to 12.93 weight percent.

5. An alloy in accordance with claim 1 wherein the range of W is 0.52 to 6.99 weight percent.

6. An alloy in accordance with claim 1 wherein the range of Ti is 1.15 to 1.22 weight percent.

7. An alloy in accordance with claim 1 wherein the range of Mn is 0.75 to 0.79 weight percent.

8. An alloy in accordance with claim 1 wherein the range of Al is 0.08 to 0.11 weight percent.

9. An alloy in accordance with claim 1 wherein the range of Co is 0.01 to 0.08 weight percent.

10. An alloy in accordance with claim 1 wherein said alloy is essentially Co free.

11. An alloy in accordance with claim 1 wherein the range of Ta is 1.18 to 4.82 weight percent.

12. An alloy in accordance with claim 1 wherein the range of Nb is 1.06 to 3.76 weight percent.

13. An alloy in accordance with claim 1 wherein the range of Hf is 1.13 to 2.77 weight percent.

14. An alloy in accordance with claim 1 wherein the range of C is 0.1 to 0.25 weight percent.

15. An alloy in accordance with claim 1 wherein said alloy is further characterized by 4.0 to 10 wt. % total precipitates, said total precipitates comprising at least one M₆C type carbide and at least one additional precipitate selected from the group consisting of MC type carbides and Ni₅M type precipitates.

16. An alloy in accordance with claim 15 wherein said alloy is further characterized by 1 to 8 wt. % M₆C type carbides.

17. An alloy in accordance with claim 15 wherein said alloy is further characterized by up to 3.5 wt. % MC type carbides.

18. An alloy in accordance with claim 15 wherein said alloy is further characterized by up to 3 wt. % Ni₅M type precipitates.

19. An alloy in accordance with claim 1 wherein said yield strength is at least 36 Ksi.

20. An alloy in accordance with claim 1 wherein said tensile strength is at least 40 Ksi.

21. An alloy in accordance with claim 1 wherein said creep rupture life is at least 72 hours.

22. An alloy in accordance with claim 1 wherein said corrosion rate is no more than 25×

10<sup>−

11</sup> g/cm²sec.

23. An alloy in accordance with claim 1 wherein said alloys is further characterized by a Mo equivalent of no less than 5.

24. An alloy in accordance with claim 1 wherein said alloy is further characterized by a corrosion susceptibility index of no less than about 0.1 and no more than about 0.2.