Liquid salt environment stress-rupture testing

Patent metadata

Field	Value
Publication number	US-9291537-B2
Application number	US-201414277274-A
Country	US
Kind code	B2
Filing date	May 14, 2014
Priority date	May 14, 2014
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

Disclosed herein are systems, devices and methods for stress-rupture testing selected materials within a high-temperature liquid salt environment. Exemplary testing systems include a load train for holding a test specimen within a heated inert gas vessel. A thermal break included in the load train can thermally insulate a load cell positioned along the load train within the inert gas vessel. The test specimen can include a cylindrical gage portion having an internal void filled with a molten salt during stress-rupture testing. The gage portion can have an inner surface area to volume ratio of greater than 20 to maximize the corrosive effect of the molten salt on the specimen material during testing. Also disclosed are methods of making a salt ingot for placement within the test specimen.

First claim

The invention claimed is:

1. A system for stress-rupture testing of materials in a high-temperature liquid salt environment, the system comprising:
a vertically elongated vessel having an upper end and a lower end, the vessel comprising one or more gas ports for maintaining a controlled inert gas environment within the vessel;
a first pull rod positioned within the vessel and extending downwardly from or through the upper end of the vessel, the first pull rod having a first specimen grip at a lower end of the first pull rod, the first specimen grip adapted to grip an upper end of a test specimen having a tubular gage portion for containing a salt;
a second pull rod positioned within the vessel below the first pull rod, the second pull rod having a second specimen grip at an upper end of the second pull rod, the second specimen grip adapted to grip a lower end of the test specimen;
a thermal break positioned within the vessel and coupled to a lower end of the second pull rod, the thermal break comprising a fixture coupled to a lower end of the second pull rod and a thermally insulating spacer supported by the fixture below the second pull rod; and
a third pull rod having an upper end spaced below the lower end of the second pull rod and spaced within the thermal break fixture, the upper end of the third pull rod being supported by the thermally insulating spacer such that the third pull rod is thermally decoupled from the second pull rod by the thermally insulating spacer, the third pull rod having a lower end that extends through a lower end of the vessel and is adapted to be coupled to a loading source for applying a load to the test specimen via the second and third pull rods and the thermal break.

2. The system of claim 1 , further comprising a load cell coupled to the third pull rod within the vessel below the thermal break, the load cell being thermally protected by the thermal break and configured to measure the load applied to the test specimen via the third pull rod.

3. The system of claim 1 , further comprising a furnace positioned around an upper portion of the vessel for maintaining the test specimen at a desired temperature that is sufficient to cause a salt within the test specimen to be in the liquid phase.

4. The system of claim 1 , wherein the thermal break fixture comprises a metallic tubular body having an upper end secured to the second pull rod and a lower end forming an inner ledge that supports a lower surface of the thermally insulating spacer.

5. The system of claim 4 , wherein the thermally insulating spacer comprises a ceramic disk and the upper end of the third pull rod comprises a flared head that contacts an upper surface of the ceramic disk and is spaced apart from the fixture and the second pull rod.

6. The system of claim 1 , wherein the vessel comprises a lower opening through which the third pull rod extends, there being a gap between the third pull rod and the lower opening such that inert process gas from within the vessel is allowed to exit the vessel through the gap.

7. The system of claim 1 , further comprising a cooling coil coupled to the third pull rod within the vessel below the thermal break.

8. The system of claim 1 , wherein the system is capable of applying a stress load to the test specimen while the test specimen is maintained at a temperature greater than 700° C.

9. The system of claim 1 , wherein the salt comprises 2 7 LiF—BeF 2 or KF—ZrF 4 .

10. A test specimen for stress-rupture testing in a high-temperature liquid salt environment, the test specimen comprising:
a first end portion having a first engagement portion for connecting to a stress-rupture testing system;
a second end portion having a second engagement portion for connecting to the stress-rupture testing system;
a narrowed gage portion between the first and second end portions; and
an inner void extending through the first end portion and through the gage portion;
wherein the gage portion has a substantially cylindrical outer surface defining an outer diameter and the inner void is substantially cylindrical within the gage portion such that the gage portion has a substantially cylindrical inner surface defining an inner diameter and the gage portion has a substantially constant wall thickness between the inner diameter and the outer diameter;
wherein the inner void is configured to receive a salt in solid form such that when the test specimen is subjected to high temperatures, the salt melts to form molten salt that completely fills the portion of the void that is within the gage portion; and
wherein a ratio Ai/V of the gage portion is at least about 20, wherein Ai is the inner surface area of the gage portion and V is the volume of material in the gage portion between the inner surface of the gage portion and the outer surface of the gage portion, in units of square inches divided by cubic inches.

11. The test specimen of claim 10 , wherein the ratio Ai/V of the gage portion is at most about 32.

12. The test specimen of claim 10 , wherein the inner diameter is in a range of from about 0.41 inches (about 10.41 mm) to about 0.44 inches (about 11.18 mm).

13. The test specimen of claim 10 , further comprising a basin ring that is attached around the test specimen below the gage portion and configured to catch liquid salt that escapes from inside the test specimen when the test specimen ruptures or leaks during stress-rupture testing.

14. A method of stress-rupture testing of a selected material in a high-temperature liquid salt environment, the method comprising:
placing a solid salt ingot within an inner void of a test specimen of the selected material and sealing the void closed;
mounting the test specimen, with the salt ingot enclosed, in a load train within a vessel of a stress-rupture testing system;
filling the vessel with an inert gas;
heating the test specimen, while mounted in the load train within the vessel filled with inert gas, such that the salt ingot melts within the void and the resulting molten salt contacts an entire inner surface of a gage portion of the test specimen;
applying a load to the gage portion of the test specimen while the test specimen is mounted in the load train within the vessel filled with inert gas and the salt is molten, and measuring the applied load until the gage portion of the test specimen fails.

15. The method of claim 14 , wherein the method further comprises continuously feeding the inert gas into the vessel while the load is applied and allowing the inert gas to escape from the vessel through a gap between the load train and a lower end of the vessel.

16. The method of claim 14 , wherein heating the test specimen comprising heating the test specimen to a temperature that is at least 100 degrees C. greater than the melting temperature of the salt.

17. The method of claim 14 , wherein measuring the applied load is performed at least in part by a load cell mounted within the load train positioned within the vessel.

18. The method of claim 14 , wherein placing the solid salt ingot within an inner void of a test specimen comprises:
placing a mold within a vacuum chamber;
creating an inert gas environment within the vacuum chamber around the mold;
heating the mold within the vacuum chamber in the inert environment to remove impurities from the mold;
after removing impurities from the mold, placing a salt into the mold and closing the mold in an inert environment;
heating the mold to melt the salt and remove voids and impurities from the salt;
cooling the mold to solidify the salt into the

Assignees

• Ut Battelle Llc

Inventors

• Ren Weiju
• Holcomb David E
• Muralidharan Govindarajan
• Wilson Dane F

Classifications

• G01N3/08 Primary

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title

• G01N3/18 Primary

  Performing tests at high or low temperatures · CPC title

• G01N2203/0226

  High temperature; Heating means · CPC title

• G01N2203/0236

  Other environments · CPC title

• G01N2203/024

  Corrosive · CPC title