阅读说明：本技术 用于无损测量氢扩散率的设备和方法 (Apparatus and method for non-destructive measurement of hydrogen diffusivity ) 是由 A.特雷迪亚 M.沙拉尼 S.A.杜瓦尔 于 2018-04-25 设计创作，主要内容包括：提供包含在金属结构的操作期间测量所述金属结构的氢扩散率的设备和方法。将氢充电表面设置在所述结构的外表面上的第一位置处。另外,将氢氧化表面设置在邻近于所述结构的所述外表面上的所述第一位置的第二位置处。产生氢通量并将其引导到所述充电表面处的金属表面中。将由所述充电表面产生的所述氢通量的至少一部分转回到所述表面。测量转移的氢通量的瞬态,并使用此测量来确定使用中的所述金属结构的所述氢扩散率。(Apparatus and methods are provided that include measuring a hydrogen diffusivity of a metal structure during operation of the metal structure. A hydrogen charging surface is disposed at a first location on an outer surface of the structure. Additionally, a hydrogen oxidizing surface is disposed at a second location adjacent to the first location on the outer surface of the structure. A hydrogen flux is generated and directed into the metal surface at the charging surface. Transferring at least a portion of the hydrogen flux generated by the charging surface back to the surface. Measuring the transient state of the transferred hydrogen flux and using this measurement to determine the hydrogen diffusivity of the metal structure in use.)

1. A method of measuring hydrogen diffusivity of a metal structure comprising:

disposing a hydrogen charging surface at a first location on an outer surface of the structure;

disposing a hydrogen oxidizing surface at a second location adjacent to the first location on the outer surface of the structure;

generating a hydrogen flux directed into a metal surface at the charging surface;

detecting a current representative of a transient of the hydrogen flux that is diverted from the metal structure back to the oxidized surface; and

determining the hydrogen diffusivity of the metal structure based on the detected hydrogen flux.

2. The method of claim 1, wherein the hydrogen charging surface is produced by a first electrochemical cell and the hydrogen oxidizing surface is produced by a second electrochemical cell.

3. The method of claim 2, further comprising adding a coating at the oxidized surface to promote oxidation of hydrogen.

4. The method of claim 3, wherein the coating comprises palladium.

5. The method of claim 2, further comprising measuring an oxidation current in the oxidation cell in order to measure the transient.

6. The method of claim 1, wherein the hydrogen diffusivity is determined from the transient of hydrogen flux using a direct simulation technique based on a Fick diffusion model using initial conditions based on experimental equipment.

7. The method of claim 6, further comprising:

setting a value of the hydrogen diffusivity;

performing the diffusion model using a set value of hydrogen diffusivity;

comparing the results of the Fick diffusion model with the results using the experimental equipment; and

repeating the previous steps with different hydrogen diffusivity values until a closest match is achieved between the results of the diffusion model and the results using the experimental apparatus.

8. The method of claim 1 wherein said hydrogen diffusivity is determined from said transient state of hydrogen flux using a simulated primary graph of a particular experimental device design, said simulated primary graph being independent of geometry and experimental parameters.

9. The method of claim 8, further comprising:

performing a sensitivity analysis on each geometric parameter to determine the effect of the parameter on the normalized transient permeability curve; and

if the curve is invariant to changes in the parameter, the curve is identified as a master curve with respect to the parameter.

10. The method of claim 9, wherein the parameters include at least two of: a metal structure thickness, a size of the charging surface, a width of the oxidized surface, and a wall thickness of the rechargeable battery.

11. The method of claim 1, wherein the measurement of hydrogen diffusivity is performed while the metal structure is in use and operational.

12. An apparatus for measuring hydrogen diffusivity of a metal structure, comprising:

a first chamber positioned on an outer surface of the metal structure, the first chamber containing a hydrogen-charged cell that generates hydrogen at a hydrogen charging surface for diffusion into the outer surface of the metal structure; and

a second chamber separated from and adjacent to the first chamber by a wall, and

positioned on the outer surface of the metal structure, the second chamber comprising an oxidation cell that creates an oxidation surface to receive a hydrogen flux transferred from the metal structure,

wherein the hydrogen diffusivity measurement is derivable from the hydrogen oxidation current within the oxidation cell.

13. The apparatus of claim 12, further comprising:

a palladium coating positioned at the oxidized surface to promote oxidation of the permeated hydrogen.

14. The apparatus of claim 13, wherein the hydrogen charging cell comprises a first electrolyte solution and the oxidation cell comprises a second electrolyte solution, the first electrolyte solution and the second electrolyte solution each in contact with the outer surface of the metal structure, a counter electrode, and a reference electrode.

15. The apparatus of claim 14, further comprising:

a first pair of electrodes positioned in the hydrogen rechargeable battery;

a second pair of electrodes and a reference electrode, both positioned in the oxidation cell;

a first power source coupled to the hydrogen rechargeable battery and configured to provide a constant current; and

a second power source coupled to the oxidation battery and configured to provide a constant voltage.

16. The apparatus of claim 13, further comprising:

an inner case surrounding the hydrogen rechargeable battery; and

an outer housing surrounding the inner housing and the oxidation cell, the oxidation cell being positioned between the inner housing and the outer housing.

17. The apparatus of claim 165, further comprising an alignment element positioned between the inner housing and the outer housing to ensure the inner chamber is concentric within the outer chamber.

18. The apparatus of claim 13, further comprising:

an inner case surrounding the oxidation battery; and

an outer housing surrounding the inner housing and the hydrogen charging battery, the hydrogen charging battery being positioned between the inner housing and the outer housing.

19. The apparatus of claim 18, further comprising an alignment element positioned between the inner housing and the outer housing to ensure the inner chamber is concentric within the outer chamber.

20. The apparatus of claim 14, further comprising:

a first sealing member for preventing leakage of the first electrolyte solution; and

a second sealing member for preventing leakage of the second electrolyte solution.

21. The apparatus of claim 20, wherein the sealing element comprises a magnet.

Technical Field

The present invention relates to material inspection and in particular to an apparatus and method for non-destructive measurement of hydrogen diffusivity.

Background

Hydrogen embrittlement is a phenomenon in which mechanical properties such as tensile strength and ductility of a metal material are deteriorated due to absorption of hydrogen. This degradation reduces the fracture resistance of metals such as steel.

Among the elements, the hydrogen atom has the smallest diameter. Hydrogen atoms are readily adsorbed on the metal surface and diffuse from the metal surface to the interior by hopping between interstitial lattices of tetrahedral/octahedral sites. Hydrogen may also be left behind at metallurgical defects and flaws in the steel such as grain boundaries, dislocations, inclusions, and the like. Once the atomic hydrogen is absorbed, it may precipitate at high stress regions where recombination reactions may occur, such as defects, inclusions, voids, or discontinuities. Recombination can lead to embrittlement, ultimately leading to cracking. This joining of high stress areas allows cracks to propagate through the metal as hydrogen accumulates.

Hydrogen diffusivity (D)_H) Is a property of metals that determines the rate at which hydrogen travels in a material and plays a major role in the development of hydrogen damage. Hydrogen damage, such as hydrogen induced cracking, is likely to grow faster in high diffusivity materials due to increased pressure build up rates. Thus, the D of a particular material of interest is accurately known_HIs the key input of a hydrogen damage evolution model and a life prediction tool.

Disclosure of Invention

According to one aspect of the present invention, a method of measuring hydrogen diffusivity of a metal structure is provided. A hydrogen charging surface is disposed at a first location on an outer surface of the structure. Further, the hydrogen oxidizing surface is disposed at a second location adjacent to the first location on the outer surface of the structure. A hydrogen flux is generated and directed into the metal surface at the charging surface. A portion of the hydrogen flux is transferred from the metal surface toward an oxidation surface where a current representing a transient state of the hydrogen flux is detected. The transient of the hydrogen flux is used to determine the hydrogen diffusivity of the metal structure. The hydrogen charging surface is produced by a first electrochemical cell and the hydrogen oxidizing surface is produced by a second electrochemical cell. In some embodiments, the method further comprises measuring an oxidation current in the oxidation cell in order to measure the transient.

In some embodiments, a coating is added at the oxidized surface to promote oxidation of hydrogen. The coating may comprise deposited palladium or a palladium foil.

In some embodiments of the method of measuring hydrogen diffusivity, hydrogen diffusivity is determined from the transient state of hydrogen flux using a direct simulation technique based on a Fickian diffusion model using initial conditions based on experimental equipment. Embodiments of these examples include setting a value for hydrogen diffusivity, performing a diffusion model using the set value for hydrogen diffusivity, comparing the results of the fick's diffusion model with the results using the experimental equipment, and repeating the previous steps with different values for hydrogen diffusivity until a closest match is achieved between the results of the diffusion model and the results using the experimental equipment.

In an alternative embodiment of the method for measuring hydrogen diffusivity, a simulated master plot of a particular experimental device design is used to determine hydrogen diffusivity, the simulated master plot being independent of geometry and experimental parameters. Implementations of these examples include performing a sensitivity analysis on each parameter to determine the effect of the parameter on the normalized transient permeation curve, and identifying the curve as a primary curve relative to the parameter if the curve is invariant to changes in the parameter. The parameters may include hydrogen charging concentration, hydrogen diffusivity of the metal structure, and general geometric parameters of the device design, such as metal structure thickness, size of the charging surface, width of the oxidized surface, and wall thickness of the charging cell.

According to another aspect of the present invention, there is provided an apparatus for measuring hydrogen diffusivity of a metal structure. The apparatus comprises: a first chamber positioned on an outer surface of the metal structure, the first chamber containing a hydrogen-charged cell that generates hydrogen at a hydrogen charging surface for diffusion into the outer surface of the metal structure; and a second chamber separated from and adjacent to the first chamber by a wall and positioned on an outer surface of the metal structure, the second chamber comprising an oxidation cell that creates an oxidation surface to receive a hydrogen flux transferred from the metal structure. The hydrogen diffusivity measurement can be derived from the hydrogen oxidation current in the oxidation cell.

In some embodiments, the apparatus further comprises a palladium coating positioned at the oxidation surface to promote oxidation of the permeated hydrogen.

According to an embodiment of the device of the invention, the hydrogen rechargeable battery comprises a first electrolyte solution and the oxidation battery comprises a second electrolyte solution, both the first electrolyte solution and the second electrolyte solution being in contact with the outer surface of the metal structure. In some embodiments, the first pair of electrodes is positioned in a hydrogen charging cell and the second pair of electrodes and the second reference electrode are positioned in an oxidation cell. A first power source is coupled to the hydrogen charging battery and is configured to provide a constant current, and a second power source is coupled to the oxidizing battery and is configured to provide a constant voltage. A reference electrode located in the oxidation cell is maintained at a constant potential and is used to determine the quality of the measurements made.

Some embodiments of the apparatus may be implemented using an inner housing surrounding a hydrogen charging cell and an outer housing surrounding the inner housing and an oxidation cell positioned between the inner housing and the outer housing. In further embodiments, an alignment element is positioned between the inner and outer housings to ensure that the inner chamber is concentric within the outer chamber.

In an alternative embodiment, the apparatus may be implemented using an inner housing surrounding the oxidation cell and an outer housing surrounding the inner housing and a hydrogen charging cell positioned between the inner housing and the outer housing. In further embodiments, an alignment element is positioned between the inner and outer housings to ensure that the inner chamber is concentric within the outer chamber.

Further embodiments of the device according to the invention comprise: a first sealing member for preventing leakage of the first electrolyte solution; a second sealing member for preventing leakage of the second electrolyte solution. In some embodiments, the sealing element comprises a magnet.

These and other aspects, features and advantages may be understood from the following description of certain embodiments of the invention and the accompanying drawings and claims.

Drawings

Fig. 1A is a front cross-sectional view of an apparatus for determining hydrogen diffusivity of a metallic material according to the prior art.

FIG. 1B is a normalized permeate flux according to the prior artGraph against normalized time τ.

Fig. 2A is a schematic cross-sectional illustration of a wall of a metal structure infiltrated by a hydrogen flux via a charging surface and an oxidizing surface in accordance with the present invention.

Fig. 2B shows an exemplary plot of charging current applied at the charging surface of fig. 2A over time.

Fig. 2C shows an exemplary plot of oxidation current measured over time for three different metallic materials.

Fig. 3A is a top cross-sectional view of an apparatus for measuring hydrogen diffusivity, employing a hydrogen flux sensor, according to an exemplary embodiment of the present invention.

Fig. 3B is a side cross-sectional view of the apparatus of fig. 3A.

Fig. 3C is a top cross-sectional view of another embodiment of an apparatus for measuring hydrogen diffusivity according to the present invention employing a hydrogen flux sensor.

Fig. 3D is a side cross-sectional view of the apparatus of fig. 3C.

Fig. 3E is a cross-sectional view of the device of fig. 3B implemented with a commercial hydrogen flux sensor.

Fig. 3F is a cross-sectional view of the apparatus of fig. 3B implemented with an ion pump for measuring hydrogen flux.

Fig. 3G is a side cross-sectional view of another embodiment of an apparatus for measuring hydrogen diffusivity according to the present invention employing a hydrogen flux sensor.

Fig. 3H is a top cross-sectional view of another embodiment of an apparatus for measuring hydrogen diffusivity according to the present invention employing a hydrogen flux sensor.

Fig. 3I is a graph showing experimental results of hydrogen flux over time detected using the apparatus of fig. 3A, 3B.

Fig. 4A is a top cross-sectional view of an apparatus for measuring hydrogen diffusivity, which employs an electrochemical cell for charging and oxidation, according to an exemplary embodiment of the present invention.

Fig. 4B is a side cross-sectional view of the apparatus of fig. 4A.

Fig. 4C is a top cross-sectional view of another embodiment of an apparatus for measuring hydrogen diffusivity using an electrochemical cell for charging and oxidation according to the present invention.

Fig. 4D is a side cross-sectional view of the apparatus of fig. 4C.

Fig. 4E is a top cross-sectional view of another embodiment of an apparatus for measuring hydrogen diffusivity using an electrochemical cell for charging and oxidation according to the present invention.

Fig. 4F is a side cross-sectional view of the device of fig. 4E.

Fig. 4G is a side cross-sectional view of another embodiment of an apparatus for measuring hydrogen diffusivity using an electrochemical cell for charging and oxidation in accordance with the present invention.

FIG. 5 is a schematic illustration of exemplary boundary conditions for a method of determining hydrogen diffusivity using direct simulation techniques, in accordance with an embodiment of the present invention.

Fig. 6 shows exemplary results of a direct simulation technique according to the present invention. The distribution of hydrogen concentration C and hydrogen flux streamlines throughout the thickness of the sample is shown.

FIG. 7A is for several different values C₀A plot of hydrogen flux (permeation) over time; FIG. 7B is for the same value C₀Normalized hydrogen flux over time.

FIG. 8 is a flow chart of a method of determining hydrogen diffusivity using standard primary map simulation techniques in accordance with an embodiment of the present invention.

FIG. 9 illustrates a simulated master graph technique by varying the value C according to the present invention₀And other parameters were held constant to simulate the results of the hydrogen flux for the apparatus of fig. 3A, 3B.

FIG. 10 illustrates a simulated master graph technique by varying the value D according to the present invention_HAnd other parameters were held constant to simulate the results of the hydrogen flux for the apparatus of fig. 3A, 3B.

FIG. 11 illustrates a simulated master graph technique by varying the value R in accordance with the present invention_chAnd other parameters were held constant to simulate the results of the hydrogen flux for the apparatus of fig. 3A, 3B.

FIG. 12 illustrates a simulated master graph technique by varying the value W according to the present invention_oxAnd other parameters were held constant to simulate the results of the hydrogen flux for the apparatus of fig. 3A, 3B.

FIG. 13 illustrates a simulated master graph technique by varying the value L according to the present invention_ccAnd other parameters were held constant to simulate the results of the hydrogen flux for the apparatus of fig. 3A, 3B.

Figure 14 shows the results of simulating the hydrogen flux of the device of figures 3A, 3B by varying the value L and keeping the other parameters constant, according to the simulated master graph technique of the present invention.

FIG. 15 illustrates the inclusion of simulated master graph techniques according to the present invention for different values of L_ccL generated plots of a set of main curves for the apparatus of fig. 3A, 3B.

Detailed Description

By way of overview, embodiments of the present invention use a portion of the outer surface of the metal structure to be investigated as a hydrogen charging surface, and an adjacent portion of the outer surface as an oxidation surface. Hydrogen atoms are generated at the charged surface, enter the metal, and then a part of the generated hydrogen atoms are diffused toward the oxidized surface in a three-dimensional flow pattern. By measuring the transient flux of all hydrogen collected at or near the oxidation surface over time, embodiments of a simulation method suitable for two-dimensional or three-dimensional hydrogen flux can be used to determine the hydrogen diffusion coefficient D_H。

As hydrogen penetrates the metal at the charging surface, it tends to diffuse into the low chemical potential (i.e., low hydrogen concentration) region at a rate proportional to the gradient of hydrogen concentration. In other words, hydrogen tends to leave the metal by taking the "shortest chemical path". In metallic structures used in industry with wall thicknesses greater than one millimeter, the shortest chemical path does not necessarily pass through the wall thickness from the outer surface to the inner surface. But rather a complex three-dimensional diffusion pattern. Fig. 2A is a schematic cross-sectional illustration of a wall of a metal structure 205 infiltrated by a hydrogen flux via a charging surface 210 and an oxidizing surface 215 in accordance with the present invention. A hydrogen flux line, such as 220, is shown that illustrates the semi-circular path that hydrogen atoms follow as they are emitted from charging surface 210 into metal 205 and then diffuse laterally and upward toward oxidizing surface 215. Embodiments of the present invention utilize these flux patterns to extract and measure residual hydrogen that exits the metallic structure 205 from the outer wall near the charging surface 210. Since such residual hydrogen has a hydrogen diffusivity D in a metal structure as a characteristic (i.e., property) of the metal material_HDiffusion (with proper surface preparation, negligible surface effects) from the start of the hydrogen flux until the flux reaches a steady state level at the oxidized surface 215 (ii) ((iii))Time elapsed for a time called "transient") and D of the metal_HCorrelated and can be used to determine D of metals_H。

Fig. 2B shows an exemplary plot of charging current applied at the charging surface 210 over time; fig. 2C shows an exemplary plot of oxidation current measured over time for three different metallic materials. The current shown in fig. 2B jumps immediately from zero to a steady current level, while the oxidation current shown in fig. 2C depends on the diffusivity (D) of the different metal materials_H1、D_H2、D_H3) Rising to a steady state level relatively quickly or slowly. It should be noted that while the steady state level of oxidation current is the same for all three curves, the curves 232, 234, 236 for each metal are different during the time period that the oxidation current rises from zero to the steady state level (i.e., the transient curve). High diffusivity is associated with short transient times and sharp curves, while low diffusivity is associated with longer transient times and slowly rising curves. Thus, FIG. 2C shows the corresponding transient curve from which the hydrogen diffusivity is derived to determine the different hydrogen diffusivities (D) of the different materials_H1、D_H2、D_H3)。

The present invention provides two different sets of devices for obtaining measurements of hydrogen flux transients. In a first set of embodiments, a hydrogen flux probe is placed near the charging surface to be exposed to the transferred hydrogen flux stream. In some embodiments, the hydrogen flux probe measures hydrogen flux with a selective detector for H2, such as FID. In a second set of embodiments, two electrochemical cells are employed to generate the oxidation current, and the transient of the oxidation current is used to represent the hydrogen flux change. In both sets of embodiments, the hydrogen flux is measured or derived over time before reaching the steady state level to determine the transient state of the hydrogen flux.

Hydrogen flux Probe example

FIG. 3A is a block diagram for non-destructive measurement D according to principles disclosed herein_HAnd fig. 3B is a side cross-section. Referring to FIG. 3B, which shows the apparatus 300 installed on a surface of a metal to be tested, the apparatus 300 comprisesAn outer casing 305 of an electrically insulating material that is also chemically resistant to weakly acidic electrolytes (e.g., electrolytes having a pH in the range of 3.5 to 4.5). Exemplary materials that meet these qualifications include polymeric compounds such as polypropylene (PP), Polyethylene (PE), Polymethylmethacrylate (PMMA), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PFTE), polyimide 11(PA 11), and Polyetheretherketone (PEEK). The outer housing 305 is hollow and may be cylindrical, but other configurations are possible. An inner housing 310, smaller in size than the outer housing 305, is positioned within the first housing. The inner housing 310 is also electrically insulative and may be made of the same or similar material as the outer housing 305. In some embodiments, inner housing 310 is also hollow and may be cylindrical. Inner housing 310 is preferably concentrically positioned within outer housing 305 when installed on a surface of a metal to be tested. The outer chamber 315 is defined as the area between the outer housing 305 and the inner housing 310; the inner chamber 317 is defined as an area inside the second housing 310. In some embodiments, the first O-ring 307 is seated within a groove on the bottom of the outer housing 305. Similarly, in some embodiments, second O-ring 312 is seated within a groove on the bottom of inner housing 310.

During the measurement operation, the outer housing 305 and the inner housing 310 are placed on the outer surface 320 of the metal structure and sealed against the surface by O-rings 307, 312. Once the interface between the bottom of the housing 305, 310 and the surface 320 is sealed, the outer chamber 315 is substantially filled (e.g., 70% to 90% of the chamber volume) with an electrolyte solution 325 shown in phantom within the outer chamber. Thus, the electrolyte 325 is in direct contact with the surface 320 of the metal structure of interest at the bottom of the outer chamber 315. The interface between the electrolyte 325 and the metal surface 320 is referred to as a "charging surface". In this arrangement, the metal surface itself serves as the working electrode. Depending on the target level of hydrogen change and the duration of the hydrogen permeation measurement performed, a series of electrolyte solutions may be employed. A buffer may be used to maintain a constant pH throughout the measurement. An exemplary solution comprises 0.1/1M sodium hydroxide, 3.5% sodium chloride, and 0.1M sulfuric acid solution.

The counter electrode 330 is positioned within the electrolyte 325 in the outer chamber 315. In some embodiments, the counter electrode 330 comprises a platinum mesh. In other embodiments, to reduce costs, carbon electrodes or other suitable electrodes that do not react with the electrolyte solution 325 under the applied potential may be used. In some embodiments, a reference electrode 335 for measuring voltage is also positioned in the outer chamber 315. Any suitable commercially available reference electrode may be used, including calomel electrode or silver-silver chloride electrode. However, the use of a reference electrode in a rechargeable battery is optional and not necessary. The annular cover 340 conforms to and fits over the outer chamber 315 and is coupled to the outer housing 305 and the inner housing 310. In some embodiments, the lid 340 is coupled to the outer housing 305 and the inner housing 310 by one or more O-rings to ensure containment of the electrolyte 325. Referring to fig. 3A, the cover 340 includes an aperture 342 through which a lead can extend to or from the counter electrode 330 and the reference electrode 335.

A power source 345 is coupled to the metal surface 320 at a negative terminal and to the lead of the counter electrode 330 at a positive terminal. In some embodiments, the power supply 345 also includes a neutral terminal of a lead to the reference electrode 335. Throughout this disclosure, it should be understood that the charging device may also be a simple DC with metal at the negative electrode and a counter electrode at the positive electrode, without the need for a reference electrode, which is optional. The power supply 345 preferably operates in a galvanostatic (i.e., constant current) mode to maintain a constant current between the metal surface 320 (working electrode) and the counter electrode 330. The constant current initiates electrolysis and generation of hydrogen atoms at the interface between the metal surface 320 and the electrolyte 325. A part of the hydrogen atoms evolved (evolve) to dihydrogen, and some sub-part of this part penetrated into the metal. If the metal surface is of sufficient thickness, for example, greater than one millimeter, then hydrogen radicals entering the metal surface diffuse in a complex flux pattern based on concentration gradients. Some of the hydrogen flux is transferred to the inner chamber 317.

A hydrogen flux sensor 350, such as a hydrogen flux sensor to detect the hydrogen flux transferred into the inner chamber 317, is positioned within the inner chamber 317. In some embodiments, a commercially available hydrogen flux is employedAnd (3) a probe. An example of a suitable hydrogen flux probe is the Hydrosteel 6000 instrument manufactured by IonScience of Cambridge, UK. The hydrogen flux sensor was selected to have sufficient sensitivity to detect approximately 1pl/cm²And s. Fig. 3E shows a view of an embodiment of the apparatus according to fig. 3A, 3B, in particular comprising a hydroteel 6000 instrument 391 and an accompanying gas conduit 392.

Fig. 3C and 3D depict top and side cross-sectional views of another embodiment of an apparatus having different geometric configurations for measuring hydrogen diffusivity. The apparatus 360 includes a single housing 365 divided by a wall 375 into a first chamber 370 and a second chamber 372. The housing 360 is rectangular, as are the first and second chambers 370 and 372. In this embodiment, a counter electrode 377 and an optional reference electrode 378 (which may be similar to the first embodiment of fig. 3A, 3B) are positioned in the second chamber 372. The second chamber 372 is filled with an electrolyte solution 380. The electrolyte solution 380 directly contacts the surface of the metal structure 320. A hydrogen flux sensor 382 comprising a gas outlet port 384 is positioned at the bottom of the first chamber 370 to receive the hydrogen flux stream transferred to the first chamber 370. A galvanostat 385 (or, alternatively, a simple DC power supply) is coupled to the metal surface 320, the counter electrode 377, and the reference electrode 378, as in the embodiment of fig. 3A and 3B. The galvanostat 385 generates a charging current that induces the production of hydrogen atoms in the electrolyte, which then diffuse into the metal surface 320. A cover 387 conforms to and covers the first and second chambers 370, 372 and contains a first opening 388 for the gas outlet port 384 and additional openings 389, 390 for the leads for the counter and reference electrodes 377, 378 to pass through.

In general, the apparatus of fig. 3A to 3D is suitable for use with various commercially available hydrogen flux sensors, and the geometric design of the chamber may be configured to suit the characteristics of the hydrogen flux sensor required in a particular application. For example, fig. 3F is a view of an embodiment of an apparatus according to fig. 3A, 3B that includes an inlet for an ion pump 393 instead of a hydrogen flux sensor. The ion pump (not shown in fig. 3F) creates a vacuum and the current required to maintain the vacuum gives an indication of the hydrogen flux.

Fig. 3G, 3H and 3I show further embodiments of the apparatus for measuring hydrogen diffusivity. The device shown in fig. 3G is the same as the device 300 of fig. 3B, but with the addition of a sealing element 396, which is included to ensure complete sealing of the charging and oxidation cell on the metal surface. The sealing element 396 may be implemented as a magnet (as shown) or, for small structures, as a strap to mechanically secure the cell to the device, to the structure to be tested. Fig. 3H is a cross-sectional view of another embodiment that is also the same as the device 300 of fig. 3A, 3B, but with the addition of an alignment element to ensure alignment between the outer and inner housings. In the depicted embodiment, the alignment element may comprise a hollow annular insert having ribs, such as 399, which may prevent relative movement between the inner and outer housings. In another embodiment, the alignment element may comprise a recess (not shown) in the cover.

In operation, if the metallic structure to be tested comprises a non-metallic coating, the coating is removed to allow direct contact between at least the charging surface of the device and the metallic surface. However, if the interface between the metal surface and the coating itself is hydrogen permeable, there is no need to remove the coating from the oxidized surface partial areas on the structure surface. After any such preliminary preparation, the device is first mounted on the surface of the metal structure. Electrolyte is then added to the outer chamber. The negative electrode of the power supply is connected to the metal structure (working electrode) and the positive electrode is connected to the counter electrode. The reference electrode is connected to a galvanostat. A constant current is then applied between the counter electrodes. The hydrogen flux is measured using a hydrogen flux sensor as the hydrogen flux changes over time (transient) within the inner chamber. The hydrogen diffusivity of the metal is then deduced from the measured hydrogen flux transient using a suitable method.

Experiments performed with the apparatus 300 of fig. 3A, 3B show that the apparatus is capable of detecting high hydrogen flux even at low current densities. Figure 3J shows a plot of hydrogen flux obtained during one such experiment over time. The high yield of detected hydrogen flux makes modeling simpler and enables the use of less sensitive hydrogen flux sensors in the device. As shown, the test may be performed over an extended period of time to reach a final steady state current (e.g., about 25 to 30 hours).

Embodiments of the apparatus comprising the above-described hydrogen flux sensor (probe) have a number of benefits and advantages. The device can be used for hydrogen diffusion for metal devices in the field of determination (D)_H) Without damaging the equipment. The application of the device requires only little surface preparation and does not require the use of expensive palladium foils or coatings. Furthermore, embodiments of the apparatus may be combined with other hydrogen flux measurement techniques and existing commercial devices. As mentioned above, the use of platinum for the counter electrode in rechargeable batteries is not mandatory. Alternative electrodes, such as carbon electrodes, may be used as long as they do not react with the electrolyte solution of the rechargeable battery.

Electrochemical Probe example

FIG. 4A is a block diagram for non-destructive measurement D according to principles disclosed herein_HAnd fig. 4B is a side cross-sectional view. Referring to fig. 4B, there is shown an apparatus 400 for mounting on a surface of a metal to be tested, the apparatus 400 comprising two electrochemical cells: a rechargeable battery 410 and an oxidation battery 420. Rechargeable battery 410 is positioned in an internal chamber 411 enclosed within an inner housing 412. The inner housing is in turn positioned within the outer housing 414. Outer chamber 415 is positioned between inner housing 412 and outer housing 414. Both outer housing 414 and inner housing 412 are made of an electrically insulating material that is also chemically resistant to weakly acidic electrolytes (e.g., electrolytes having a pH in the range of 3.5 to 4.5). Exemplary materials that meet these qualifications include polymeric compounds such as polypropylene (PP), Polyethylene (PE), Polymethylmethacrylate (PMMA), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PFTE), polyimide 11(PA 11), and Polyetheretherketone (PEEK). In the embodiment of fig. 4B, inner housing 412 and outer housing 414 are hollow and may be cylindrical, although other configurations may be used. Inner housing 412 is preferably concentrically positioned within outer housing 414 when installed on a surface of a metal to be tested. The inner chamber 411 contains an electrolyte solution 416, the electrolyte solution 416 being in direct contact with the outer surface 430 of the metal structure to be tested. Electrolyte 416 and metal surface430 is referred to as a "charging surface". Depending on the target level of hydrogen change and the duration of the hydrogen permeation measurement performed, a series of electrolyte solutions may be employed. A buffer may be used to maintain a constant pH throughout the measurement. An exemplary solution comprises 0.1/1M sodium hydroxide, 3.5% sodium chloride, and 0.1M sulfuric acid solution.

A counter electrode 417, which serves as the cathode of the rechargeable battery, and an optional reference electrode 418 for accurate voltage measurements are positioned in the electrolyte 416. In some embodiments, counter electrode 417 is a platinum mesh similar to that used in standard electrochemical cells. The reference electrode 418 may be implemented as a standard calomel electrode. To contain the electrolyte 416 within the inner chamber 411, an O-ring 419 is coupled to the bottom of the inner housing 412, and the O-ring 419 is coupled to the bottom of the outer housing 414 by being inserted into a groove (not shown). An electrical DC power source 440 to provide a constant current is coupled to the metal surface 430 at a negative terminal, the counter electrode 417 at a positive terminal, and the reference electrode 418 at a neutral terminal in embodiments employing a reference electrode. The power source 440 creates a potential difference between the metal surface 430 and the counter electrode 417, which causes ionic current and also causes a certain amount of hydrolysis of water molecules at the metal surface. A part of the hydrogen atoms evolves to dihydrogen, and a sub-part of this part penetrates/diffuses into the metal.

An oxidation cell 420 is located in the outer chamber 415 of the apparatus 400. The oxidation cell 420 includes a counter electrode 421 and a reference electrode 422 positioned within the outer chamber 415. Counter electrode 421 and reference electrode 422 can be implemented using materials similar to those used for counter electrode 417 and reference electrode 418, respectively. The outer chamber 415 is filled with an electrolyte solution 423, the electrolyte solution 423 directly contacting the metal surface 430 at the "oxidized surface". The electrolyte solution 423 may, but need not, have the same characteristics as the electrolyte 416 of the rechargeable battery 410. In some embodiments, a 0.1/1M sodium hydroxide solution may be used for the electrolyte 423, although a variety of other solutions may be used. To contain the electrolyte 423 within the outer chamber 415, an O-ring 424 is coupled to the bottom of the outer housing 414. A power source 445 to provide a constant voltage (voltage source mode) is coupled to the metal surface 430 at the positive terminal, coupled to the counter electrode 421 at the negative terminal, and coupled to the reference electrode 422 at the neutral terminal by being inserted into a groove (not shown).

A coating 450, preferably made of palladium, is deposited on the oxidized surface of the metal in contact with the electrolyte 423 of the oxidation cell 420. The coating 450 promotes the oxidation of hydrogen atoms that reach the oxidized surface. The coating may be prepared in any manner known to those skilled in the art. The cover 460 fits over and fits over the inner chamber 411 and the outer chamber 415. Referring to fig. 4A, lid 460 includes a first pair of openings 461, 462, the first pair of openings 461, 462 being positioned to allow electrical leads to couple counter electrode 417 and reference electrode 418 to power source 440 when the lid is in place over inner chamber 411. Similarly, cover 460 includes a second pair of openings 463, 464 to allow electrical leads to couple counter electrode 421 and reference electrode 422 to power source 445.

Fig. 4C and 4D depict top and side cross-sectional views of another embodiment of an apparatus for measuring hydrogen diffusivity, where the locations of the rechargeable and oxidizing cells are swapped. Referring to fig. 4D, device 470 comprises two electrochemical cells: an oxidation cell 475 and a rechargeable cell 485. The oxidation cell 475 is positioned in an internal chamber 471 enclosed within the inner housing 472. The inner housing 472 is in turn positioned within an outer housing 474. The rechargeable battery 485 is positioned in an outer chamber 476, the outer chamber 476 being positioned between the inner housing 472 and the outer housing 474. Both the inner housing 472 and the outer housing 474 are made of electrically insulating material that is also chemically resistant to weakly acidic electrolytes, such as those described above with respect to the apparatus of fig. 4A and 4B.

The internal chamber 475, which includes the oxidation cell, contains an electrolyte solution 477, the electrolyte solution 477 being in direct contact with an exterior surface 490 of the metal structure to be tested. In some embodiments, a 0.1/1M sodium hydroxide solution may be used for the electrolyte 477, although a variety of other solutions may be used. The bottom of the inner housing 472 may contain or be coupled to a sealing element, such as an O-ring 481, to prevent leakage of the electrolyte 477. In this embodiment, the interface between electrolyte 477 and metal surface 490 is an oxidized surface. A coating 484 preferably made of palladium is deposited on the oxidized surface of the metal in contact with the electrolyte 477 of the oxidation cell 475. Counter electrode 478 and reference electrode 479 are positioned in electrolyte solution 477. A power source 495, operable as a constant voltage source, is coupled to the metallic surface 490 at a positive terminal, to the counter electrode 478 at a negative terminal, and to the reference electrode 479 at a neutral terminal. The outer chamber 485 containing the rechargeable battery also contains an electrolyte solution 486, which electrolyte solution 486 may be similar to the solution for the rechargeable battery described above with reference to fig. 4A, 4B. The bottom of the outer housing 474 may contain or be coupled to a sealing element, such as an O-ring 482, to prevent leakage of the electrolyte 486. In this embodiment, the interface between electrolyte 486 and metal surface 490 is a charging surface. Counter 487 and reference 488 (optional) electrodes are positioned in electrolyte solution 486. A power source 497 operable as a constant current source is coupled to the metal surface 490 at a positive terminal, to the counter electrode 487 at a negative terminal, and optionally to the reference electrode 488 at a neutral terminal. The cover 483 conforms to and fits over both the inner chamber 471 and the outer chamber 476 and contains openings (not shown) for electrical leads to the electrodes of the device 470.

Notably, the power sources 440, 445, 495, 497 in the depicted embodiment are coupled to and controlled by a computing device (not shown) that can modify the respective applied currents and voltages to achieve accurate hydrogen detection control.

Fig. 4E and 4F show another embodiment of the apparatus for measuring hydrogen diffusivity according to the present invention. The configuration of the device 491 is similar to that shown in fig. 3C and 3D above (i.e., rectangular and dual chamber), except that the device 491 contains both a rechargeable battery 492 and an oxidizing battery 493. Otherwise, the apparatus of fig. 4E and 4F is similar to the other electrochemical cell embodiments described with reference to fig. 4A through 4D. Another embodiment of an apparatus 498 for measuring hydrogen diffusivity shown in fig. 4G is the same as apparatus 300 of fig. 4B, except that a sealing member 499 is added, which sealing member 499 is included to ensure complete sealing of the charging and oxidation cell on the metal surface. The sealing element 499 may be implemented as a magnet or, for small structures, as a tape to mechanically secure the battery to the device to the structure to be tested.

In operation, if the metallic structure to be tested contains a non-metallic coating, the coating is removed. After such preliminary preparation, the device is first mounted on the surface of the metal structure. The electrolyte is then added to the oxidation cell. The voltage between the oxidized surface of the working electrode and the reference electrode of the oxidation cell was then set at about +300mV using a power supply configured in a constant voltage mode. Upon oxidation of the oxidation current I in the cell_oxUpon stabilization, electrolyte is added to the rechargeable battery. A constant charging current is then set using the power supply configured in the constant current mode. Monitoring the oxidation current (I) of the oxidation cell as soon as the charging current starts_ox) Until a steady state is reached, the transient representing the hydrogen flux. The hydrogen diffusivity of the metal is then deduced from the transient state of the oxidation current using a suitable method.

Method for determining hydrogen diffusivity

D cannot be used to determine multidimensional hydrogen flow due to the standard time-lag method developed under one-dimensional diffusion approximation_HTherefore, the present invention provides 1) a direct simulation method and 2) a simulation of the main graph method to determine D_H.

Direct simulation method

In the direct simulation method, a different D is used at each optimization step (e.g., using finite elements)_HValue (incremental method) to solve the optimization problem, wherein the hydrogen diffusion kinetics are determined by having an apparent diffusivity D_HFeick diffusion model estimation). In other words, the direct simulation method simulates and best fits the field results for each single-field measurement (otherwise known as the inverse problem). In this method, the direct simulation method may employ a finite element analysis technique. When the best fit between the numerically simulated permeability curve and the experimentally measured permeability curve is obtained, the sub-iterative simulation is stopped and the best D is reached_H。

The diffusion model that requires a solution at each iteration is given in equation 4. A set of boundary conditions and initial conditions depending on the device design and service conditions are associated with equation 4.

Fig. 5 illustrates boundary conditions associated with a device 300 such as the design of fig. 3A, 3B. The boundary condition includes a hydrogen charge concentration (C)₀) Thickness of test metal (L), wall thickness of rechargeable battery (L)_cc) Radius of the charging surface (R)_ch) (more generally, the size of the charging surface) and the width (W) of the oxidized surface_ox). Fig. 6 shows a typical solution to the above boundary value problem, and fig. 6 shows the distribution of streamlines of hydrogen concentration C and hydrogen flux throughout the thickness of the sample.

In this optimization, the hydrogen charge concentration (C) provided by the rechargeable battery₀) Is arbitrary and does not affect the value of the normalized steady state permeate flux at the oxidized surface. This is illustrated by comparing fig. 7A with fig. 7B. FIG. 7A is for several different C₀Value, hydrogen flux (permeation) versus time. As shown, for each C₀The values, steady state permeation, are different. FIG. 7B is for the same C₀Values, normalized hydrogen flux versus time. It can be seen that fig. 7B shows a single curve, indicating that the normalized flux converges to all C₀The same value of the values. In other words, the optimization problem should be performed taking into account the normalized flux rather than the actual flux.

Method for simulating main graph

In the simulation of the master graph approach, a series of "master curves" are generated for a particular device design. D can then be determined from the measured penetration transients using the master curve_HThe value of (c). Once developed for a given device design, the master graph becomes a feature of the particular design. In this section, a set of master curves is derived from the device design of fig. 4A, 4B. However, the same method may be applied to other device designs as well, and none of the following description should be taken as limiting the method to a particular design.

By definition, the main curve is independent of the geometry of the device concerned, as well as of the thickness of the test metal surface, the hydrogen diffusivity value and the hydrogen charge concentration of the metal. In order to obtain a master curve independent of these parameters, the following steps are performed. First, the measured penetration transient J is listed_perm(t) all parameters of influence. Sensitivity analysis is then performed on each parameter by varying it one at a time to determine each parameter pairAndthe influence of the plot of (a). A plot, referred to as a "Normalized Penetration Transient (NPT) plot," is considered a master curve if it remains constant as the parameter changes. If the plot does not remain constant, the x-axis parameters are changed and, if desired, a limit on the variability of the test parameters is introduced. This process is described in more detail below.

FIG. 8 is a flow chart of an embodiment of a method 800 for determining hydrogen diffusivity using standard master map simulation techniques in accordance with the present invention. This flow chart is suitable for the devices depicted in fig. 4A and 4B, and in general the particular parameters tested may vary depending on the device design employed, including its physical parameters. In a first step 810, parameters that may affect the penetration transient are listed. For this embodiment, the parameter may include the radius (R) of the hydrogen charging surface_ch) Width of oxidized surface (W)_ox) Thickness of the metal tested ("coupon") (L) and wall thickness of the rechargeable battery (L)_cc). In the following step 820, each parameter is fixed to a reference value. A table of exemplary reference values is given in table 2 below.

TABLE 2

Parameter(s)	Reference value	Range of variation	Unit cell
				L	10	[5-30]	Mm
Rch	L	[0.5L-5L]	Mm
				Wox	L	[0.5L-5L]	Mm
Lcc	L/2	[0.5L-2L]	Mm

In step 840, R is changed for different values within the range of variation_ch(radius of the charging surface) while keeping all other parameters constant. At each delta change, in step 842, based on R_chThe values perform a parametric simulation. FIG. 11 shows the effect of changing R_chResults of experimental simulations performed. With respect to this variable, when R_chIs increased to or above the specimen thickness (i.e., R)_ch≧ L), the NPT plot becomes for R_chThe further increase in (c) is constant. Thus, suppose R_ch≧ L, then NPT can be considered as the master curve.

In step 844, W is changed for different values within the range of variation_oxThe value of (width of the oxidized surface) while keeping all other parameters constant. At each change increment, at stepAt 846, parametric simulations are performed based on the Wox value. FIG. 12 shows the result obtained by changing W_oxResults of experimental simulations performed. Similar to the Rch parameter, when Wox increases to or above the specimen thickness (W)_ox≧ L), the NPT plot becomes for W_oxThe further increase in (c) is constant. Thus, suppose W_ox≧ L, then NPT can be considered as the master curve.

In step 848, L is changed for different values within the range of variation_cc(wall thickness of the rechargeable battery) while keeping all other parameters constant. At each delta, in step 850, based on L_ccThe values perform a parametric simulation. FIG. 13 shows the result of changing L_ccResults of experimental simulations performed. As indicated in FIG. 13, the NPT plot shows the correlation to L_ccApparent dependence of the value (i.e., it is relative to L)_ccNot constant). This dependency can be explained by the fact that: the width of the rechargeable battery has a substantial effect on the shortest path that hydrogen can travel to reach the oxidation surface.

Similarly, in step 852, the value of L (the thickness of the metal coupon) is changed for different values within the range of variation, while all other parameters are held constant. At each delta, in step 854, a parametric simulation is performed based on the L value. FIG. 14 shows a method for changing L_ccResults of experimental simulations performed. Fig. 14 indicates that NPT is also not constant relative to L, which also affects the shortest path for hydrogen diffusion.

By using L_ccRatio to L (i.e., L)_cc/L), two variables affecting the NPT plot can be converted into a single control parameter for the main curve position. Suppose a condition R_ch、W_ox≧ L, then different L's can be targeted_ccthe/L value produces a set of master curves. For the apparatus 400 of fig. 4A, 4B, fig. 15 shows a set of main hydrogen permeation curves. The tabulated values of the curves are presented in table 3.

TABLE 3

It should be noted that in some embodiments, it may be possible to replace the abscissa parameter with a different parameterSo that a single main curve is generated for all Lcc values. However, in many cases, it is preferable to maintain the abscissa parameter in order to be in overall agreement with the standard plot of ISO-17081.

Returning to fig. 8, in step 855, master curves are combined for each of the parameters (for invariant parameters, the NPT plot is used as the master curve). In step 860, once the master curve is generated, the experimentally measured hydrogen flux transient may be used to determine D using the master curve_HThe value of (c). Although any point on the main curve may be used, it is generally used thereinPoint on the curve of (2). D can then be calculated according to_H：

Wherein the value t_lagIs determined from experimental measurements. Tau is_lagIs in accordance with the value corresponding to the experimental value L_ccThe main curve of/L is directly determined. Table 4 shows the tabulated values τ of the different principal curves_lag(i.e., different values of L)_ccL). The method then ends at step 870.

TABLE 4

The disclosed apparatus and method provide several advantageous features. It is apparent that the disclosed apparatus and method enable the hydrogen diffusivity of a metallic apparatus to be determined while the apparatus is in operation, i.e., while the metallic structure is subjected to internal pressure (hoop stress, etc.) and process temperature.

Some of the methods disclosed herein are intended to be implemented using a programmed computer system. The flowchart and block diagrams that illustrate the methods may represent modules, segments, or portions of code, which comprise one or more executable instructions for implementing the specified logical functions. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

It is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the system and method, but are instead provided as representative embodiments and/or arrangements for teaching one skilled in the art one or more ways to implement the method.

It should be understood that while many of the foregoing descriptions have been directed to systems and methods for implanting photonic materials, the methods disclosed herein may similarly employ other 'smart' structures in contexts, situations and scenarios beyond those referenced. It is to be further understood that any such embodiments and/or deployments are within the scope of the systems and methods described herein.

It should be further understood that throughout the several drawings, like numerals indicate like elements, and that not all of the components and/or steps described and illustrated with reference to the drawings are required for all embodiments or arrangements.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The directional terminology used herein is for the purpose of convention and reference only and is not to be construed as limiting. However, it should be recognized that these terms may be used with reference to a viewer. No limitation is therefore implied or inferred.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.