# US 9,435,011 B2 · Creep-resistant, cobalt-free alloys for high temperature, liquid-salt heat exchanger systems

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- Number: US 9,435,011 B2
- Document ID: US9435011B2
- Status: Granted
- Kind: B2
- Application number: 13/962,197
- Filed: 2013-08-08
- Published: 2015-02-12
- Granted: 2016-09-06
- Earliest claimed: 2013-08-08
- Assignees: UT-Battelle, LLC
- Applicants: UT-Battelle, LLC
- Inventors: David E. Holcomb; Govindarajan Muralidharan; Dane F. Wilson
- Web page: https://patentgrep.com/patent/US9435011B2

## CPC

- C22C 19/057: {with the maximum Cr content being less 10%}
- C22C 19/007: {with a light metal (alkali metal Li, Na, K, Rb, Cs; earth alkali metal Be, Mg, Ca, Sr, Ba, Al Ga, Ge, Ti) or B, Si, Zr, Hf, Sc, Y, lanthanides, actinides, as the next major constituent}
- C22F 1/10: of nickel or cobalt or alloys based thereon
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C22F: CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass, C23F17/00)

## Abstract

An essentially Fe- and Co-free alloy is composed essentially of, in terms of weight percent: 6.0 to 7.5 Cr, 0 to 0.15 Al, 0.5 to 0.85 Mn, 11 to 19.5 Mo, 0.03 to 4.5 Ta, 0.01 to 9 W, 0.03 to 0.08 C, 0 to 1 Re, 0 to 1 Ru, 0 to 0.001 B, 0.0005 to 0.005 N, balance Ni, the alloy being characterized by, at 850° C., a yield strength of at least 25 Ksi, a tensile strength of at least 38 Ksi, a creep rupture life at 12 Ksi of at least 25 hours, and a corrosion rate, expressed in weight loss [g/(cm2 sec)]10−11 during a 1000 hour immersion in liquid FLiNaK at 850° C., in the range of 3 to 10.

## Claims

### Claim 1

An essentially Fe- and Co-free alloy for use in contact with liquid fluoride salts consisting essentially of, in terms of weight percent:
Cr 6.0 to 7.5
Al 0 to 0.15
Mn 0.5 to 0.85
Mo 11 to 19.5
Ta 0.3 to 4.5
W 0.01 to 9
C 0.03 to 0.08
Re 0 to 1
Ru 0 to 1
B 0 to 0.001
N 0.0005 to 0.005
Ni balance, wherein Mo+W is 19.85 or less, and Mo+Cr is 26.37 or less;
said alloy being characterized by, at 850° C., a yield strength of at least 25 Ksi, a tensile strength of at least 38 Ksi, a creep rupture life at 12 Ksi of at least 25 hours, and a corrosion rate, expressed in weight loss [g/(cm2 sec)]10−11 during a 1000 hour immersion in liquid FLiNaK at 850° C., in a range of 3 to 10, said alloy has a microstructure consisting of γ phase and M6C, wherein M6C is 1 to 2.5 in wt %, and having a corrosion susceptibility index between 0.09 and 0.12.

### Claim 2 (depends on 1)

An alloy in accordance with claim 1 wherein the range of Cr is 6.7 to 7.1 weight percent.

### Claim 3 (depends on 1)

An alloy in accordance with claim 1 wherein the range of Al is 0.05 to 0.12 weight percent.

### Claim 4 (depends on 1)

An alloy in accordance with claim 1 wherein the range of Mn is 0.7 to 0.8 weight percent.

### Claim 5 (depends on 1)

An alloy in accordance with claim 1 wherein the range of Mo is 11.5 to 19 weight percent.

### Claim 6 (depends on 1)

An alloy in accordance with claim 1 wherein the range of Ta is 0.4 to 4.1 weight percent.

### Claim 7 (depends on 1)

An alloy in accordance with claim 1 wherein the range of C is 0.04 to 0.06 weight percent.

### Claim 8 (depends on 1)

An alloy in accordance with claim 1 wherein said yield strength is at least 27 Ksi.

### Claim 9 (depends on 1)

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

### Claim 10 (depends on 1)

An alloy in accordance with claim 1 wherein said creep rupture life is at least 28 hours.

### Claim 11 (depends on 1)

An alloy in accordance with claim 1 wherein said corrosion rate is no more than 9.3.

### Claim 12 (depends on 1)

An alloy in accordance with claim 1 wherein said alloy is further characterized by a wt. % M6C in the range of 1.12 to 2.2.