阅读说明：本技术 涡轮机发动机部件的钎焊修复 (Braze repair of turbine engine components ) 是由 K.奥兹贝萨尔 于 2017-05-26 设计创作，主要内容包括：用于高γ’镍基燃气涡轮机部件(1)的结构钎焊修复的系统(10)和方法(1000)。该系统可包括控制器(200),其可操作地连接到例如真空炉的加热系统(100),用于在指定或预定的时间段内控制该炉的加热温度。受损部件被放置在炉中并加热至第一温度,该第一温度被保持指定的时间段,然后被冷却至大约室温。然后,该部件被加热至高于该第一温度的第二温度,该第二温度被保持第二时间段,然后再次被冷却至大约室温。在冷却之后,该部件可在第三时间段内在等于或高于先前温度的第三温度下进行钎焊修复。(A system (10) and method (1000) for structural brazing repair of a high gamma prime nickel-based gas turbine component (1). The system may include a controller (200) operatively connected to a heating system (100), such as a vacuum furnace, for controlling the heating temperature of the furnace for a specified or predetermined period of time. The damaged part is placed in an oven and heated to a first temperature, which is maintained for a specified period of time, and then cooled to about room temperature. The part is then heated to a second temperature that is higher than the first temperature, the second temperature is maintained for a second period of time, and then cooled again to about room temperature. After cooling, the component may be braze repaired at a third temperature equal to or greater than the previous temperature for a third period of time.)

1. A method, comprising:

heating the damaged part (1) to a first temperature and holding at the first temperature for a first period of time to dissolve the grain boundary eutectic;

cooling the component;

heating the damaged part to a second temperature greater than the first temperature and holding the second temperature for a second period of time to further dissolve the grain boundary eutectic; and

cooling the component.

2. The method of claim 1, wherein the heating of the damaged component is by slow heating to at least one of the first temperature and the second temperature.

3. The method of claim 2, wherein the slow heating is performed at a heating rate of 2-5 ℃/minute.

4. The method of claim 1, wherein the heating of the damaged component is by rapid heating to a first threshold temperature below the first temperature, followed by slow heating to at least one of the first temperature and the second temperature.

5. The method of any of claims 1-4, further comprising:

after the component is cooled, the damaged component is braze repaired at a braze temperature.

6. The method of claim 5, further comprising:

heating the component to a third temperature and holding the third temperature for a third period of time to dissolve the grain boundary eutectic prior to brazing to repair the damaged component.

7. The method of claim 7, further comprising:

cooling the component after the third period of time and prior to braze repair.

8. The method of claim 5, wherein the braze repair of the component is between 0.1 and 12 hours.

9. The method of claim 6, wherein the third temperature is equal to or greater than one of the first temperature and the second temperature.

10. The method of claim 5, wherein the brazing temperature is achieved by a rapid heating rate.

11. The method of claim 10, wherein the rapid heating rate is from about 10 ℃/minute to about 30 ℃/minute.

12. The method of claim 5, wherein the brazing temperature is a grain boundary eutectic melting temperature.

13. The method of claim 5, wherein the brazing temperature is equal to or greater than any of the first temperature and the second temperature, and wherein the brazing temperature is achieved by a rapid heating rate.

14. The method of claim 13, wherein the rapid heating rate is about 10-30 ℃/minute.

15. The method of claim 1, further comprising:

preparing the damaged component for repair prior to heating the component to the first temperature.

16. The method of claim 15, wherein preparing the damaged component comprises removing any coating from the damaged component.

17. The method of claim 16, wherein the coating is removed by a chemical or mechanical process.

18. The method of claim 15, wherein preparing the damaged component comprises removing oxide from cracks of the damaged component.

19. The method of claim 18, wherein the oxide is removed by a fluoride ion cleaning process.

20. The method of claim 1, wherein the first temperature is higher than a newly manufactured part Solution Treatment Temperature (STT) of the damaged part.

21. The method of claim 20, wherein the first temperature is about 10 ℃ above the STT.

22. The method of claim 1, wherein at least one of the first time period and the second time period is between 1 hour and 2 hours.

23. The method of claim 1, wherein heating to the second temperature is initiated before the component cools to room temperature.

24. The method of any of claims 1-4, further comprising:

the component is tested by non-destructive testing before it is returned to service.

25. The method of claims 1-4, further comprising:

applying at least one coating to a surface of the component prior to returning the component to service.

26. A system 10 comprising:

a heating system (100) operably configured to generate a heating temperature up to or exceeding a component grain boundary eutectic melting temperature; and

a controller (200) operatively connected to the furnace for controlling the furnace heating temperature over a specified time period;

wherein the controller is operable to heat the furnace to a first temperature at a first heating rate and maintain the first temperature reached for a first period of time while the heating system is carrying a damaged part;

wherein at the end of the first period of time, the first temperature is no longer maintained and the component is allowed to cool; and

wherein, upon cooling the component after the first time period, the controller causes the heating system to heat the component to a second temperature at a second heating rate, and wherein the second temperature reached is maintained for a second time period, and wherein the component is cooled after the second time period.

27. The system of claim 26, wherein the second temperature is greater than the first temperature.

28. The system of claim 26, wherein the cooling of the component is by a cooling system operatively connected to the furnace and optionally to the controller.

29. The system of claim 26, wherein upon cooling the component after the second period of time, the controller causes the furnace to heat to a third temperature equal to or greater than either of the first temperature or the second temperature, wherein the third temperature is reached by slow heating, and wherein the reached third temperature is maintained for a third period of time.

30. The system of claim 29, further comprising:

cooling the component after the third period of time.

31. The system of any one of claims 26-30, wherein the first temperature is higher than a newly manufactured part Solution Treatment Temperature (STT) of the damaged part.

32. The system of claim 26, wherein the first temperature and the second temperature are achieved by slow heating.

33. The system of claim 32, wherein the slow heating is performed with a slow heating rate of about 2-5 ℃/minute.

34. The system of claim 26, wherein the first temperature and the second temperature are achieved by rapid heating followed by slow heating.

35. The system of claim 34, wherein rapid heating reaches a threshold temperature that is less than the first temperature.

36. The system of claim 35, wherein the rapid heating to the threshold temperature is performed by a rapid heating rate of about 10-30 ℃/minute, and wherein the slow heating to the first temperature or the second temperature is performed by a slow heating rate of about 2-5 ℃/minute.

37. The system of claim 26, wherein the heating system is selected from the group consisting of a vacuum furnace, a vacuum furnace having a partial pressure, an endothermic gas heat treatment furnace, or an induction heating system.

Technical Field

The present disclosure relates generally to the field of materials technology, and more particularly, to systems and methods for braze repair of industrial components, such as components of turbine engines, such as gas turbine engines.

Background

In a turbomachine, such as a gas turbine engine, air is pressurized in a compressor section, then mixed with fuel and combusted in a combustion section to produce hot combustion gases. The hot combustion gases expand within the turbine section of the engine where energy is extracted to provide output power to produce electricity. The hot combustion gases travel through a series of stages as they pass through the turbine section. One stage may include a row of stationary airfoils, i.e., vanes, followed by a row of rotating airfoils, i.e., blades, wherein the blades extract energy from the hot combustion gases to provide output power. Because components within the combustion and turbine sections are directly exposed to the hot combustion gases, these components may be damaged and require repair.

Structural braze repair of these components is difficult due to the high viscosity of the braze material. Increasing the brazing temperature to reduce the viscosity results in melting of the grain boundaries of the part. Grain boundary melting is undesirable and makes the part less effective.

Disclosure of Invention

In one embodiment, a method for braze repairing one or more components of a turbine engine is provided. The method includes heating the damaged component to a first temperature, for example, at a slow heating rate, and maintaining the first temperature for a first period of time. The first time period may be a predetermined or specified amount of time. At the end of the first period of time, the part is allowed to cool, for example to room temperature or approximately room temperature, and then the part is heated again to a second temperature, which is maintained for a second period of time. The second temperature may be equal to or higher than the first temperature. The second time period may be equal to or different from the first time period. At the end of the second period, the component is cooled again. Thereafter, the component may be inspected, for example, by non-destructive testing and based on the amount of remaining grain boundary eutectic, the component may be subjected to a third heat treatment similar to either of the first or second heat treatments, or a brazing operation of the damaged component may be initiated at, for example, a rapid heating rate.

In another embodiment, a system for preparing a component for braze repair or braze repairing the component is provided. The system may include a controller operatively connected to the heating system and optionally to the cooling system. The heating system may be operably configured to produce a heating temperature up to or exceeding the melting temperature of the component or, for example, the grain boundary eutectic melting temperature. The cooling system may be operably configured to cool or facilitate cooling of the component to about room temperature, for example, for inspection of the component to determine if further heat treatment may be required. In operation, a damaged component may be carried by the heating system, and the controller may cause the heating system to generate heat to a first temperature that, once reached, is maintained for a first period of time. The component may then be cooled by the cooling system and/or naturally by reducing the heat generated by the heating system. Upon cooling of the component to, for example, room temperature, or during a cooling phase, the component is subjected to a second heat treatment, wherein the component is heated to a second temperature, for example by a slow heating rate, and once the second temperature is reached, the second temperature is maintained for a second period of time. The component is again cooled and may be inspected to determine whether to initiate a braze repair operation or to perform a subsequent heat treatment to further dissolve the grain boundary eutectic before the component is brazed.

Drawings

FIG. 1 illustrates a schematic view of a damaged component used in a turbine engine before braze repair and after a conventional braze repair method that results in melting of grain boundaries;

FIG. 2 illustrates a block diagram of an embodiment of a system for structural brazing repair in accordance with the disclosure provided herein;

FIG. 3 illustrates an exemplary embodiment of a controller that may be used in the system of FIG. 2 in accordance with the disclosure provided herein;

FIG. 4 illustrates a schematic view of the damaged component of FIG. 1 after a step of a repair operation has been performed in accordance with the disclosure provided herein, wherein the grain boundary eutectic portion dissolves and shrinks;

FIG. 5 illustrates a schematic view of the damaged component of FIG. 1 undergoing another step in a repair operation with further dissolution and shrinkage of the grain boundary eutectic according to the disclosure provided herein;

FIG. 6 illustrates a schematic view of the damaged component of FIG. 1 undergoing yet another step in a repair operation, where the grain boundary eutectic is even further dissolved and much smaller after undergoing the repair operation, in accordance with the disclosure provided herein; and

FIG. 7 illustrates a block diagram of a method for braze repair of a component according to the disclosure provided herein.

Detailed Description

Referring now to the drawings, wherein the showings are for the purpose of illustrating embodiments of the subject matter herein only and not for the purpose of limiting the same, FIG. 1 is a schematic illustration of a turbine engine component, such as a gas turbine engine component, having a common grain boundary low melting point eutectic in its metallographic structure (metallurgical structure) before and after a conventional braze repair process, which results in melting of the grain boundary eutectic.

It will be appreciated that under conventional braze repair methods, when the brazing operation is performed at a temperature above the grain boundary melting temperature of the component, undesirable grain boundary eutectic melting occurs.

Thus, under conventional methods, the brazing temperature and the heating rate applied to the brazing temperature during the brazing operation are limited due to the presence of grain boundary eutectic.

The present inventors have recognized the above limitations and identified weaknesses in conventional approaches. The present inventors now teach a new technique for brazing or weld repair, such as structural repair, of damaged parts having grain boundary eutectic portions.

Referring now to FIG. 2, a block diagram of an exemplary embodiment of a braze repair system 10, for example, for a high gamma prime nickel-based gas turbine component 1 is shown. As shown in fig. 2, the system 10 may include a heating system 100 operable to generate heat up to or above the melting temperature of eutectic grain boundaries, e.g., a temperature between 0 and 3000 ℃. In one embodiment, the heating system 100 may be a furnace. The furnace 100 may be, for example, a vacuum furnace or an endothermic gas heat treatment furnace having a partial pressure. Additionally or alternatively, the thermal system 100 may be an induction heating system or other heating system that is selected with sound judgment and operable to generate heat up to or above the melting temperature of eutectic grain boundaries.

It should be recognized that an oven capable of producing lower or higher temperatures than those mentioned above may also be used when selected with sound judgment and based on the melting temperature of the article and/or the materials therein.

The system 10 may also include one or more controllers 200 operatively connected to the furnace 100, e.g., via a wired or wireless connection 15, and configured to control the heating temperature of the furnace for a specified or predetermined period of time. In the exemplary embodiment of fig. 3, the controller 200 may include: a processor 202, operatively connected to the memory 204, for executing one or more instructions or commands of the control application 300 carried by the memory 204; or other data storage system 206, such as a hard disk drive, solid state drive, etc., operatively connected to the processor 202. The controller may also include a user interface (not shown), which may be any general purpose interface for receiving user input and generating displayable output on a display (not shown). The controller 200 may also include a network adapter/transceiver 208 to facilitate communication between the controller 200 and other devices of the system 10, for example, to receive and transmit operational or production information related to the furnace 100 and/or other cooling devices. It should be understood that the controller 200 may be carried by the furnace 100, i.e., connected to the furnace 100, or the controller 200 may be remote from the furnace 100. The series of instructions for controlling the application 300 may include instructions for operating the furnace at a particular temperature for a specified period of time. Additionally or alternatively, the control application 300 may include: instructions for operating one or more devices to cool the component 1, for example to room temperature; and instructions for processing temperature or temperature-related information, for example, from one or more sensor assemblies operatively carried by the furnace 100, in order to identify the temperature surrounding the component 1.

The system may also include a cooling system, apparatus or device 130 operatively connected to the furnace 100 and/or the controller 200, for example, for cooling the component 1. The cooling device 130 may be a unit separate from the furnace 100 or system of furnaces that is operable to cool any components therein to a specified temperature or state, such as room temperature.

With continued reference to the figures, and now with reference to fig. 4-7, a method 1000 for braze repairing a component, such as a damaged component having grain boundary eutectics, is provided. After removing damaged component 1, for example from a turbine engine, method 1000 may begin with the step of preparing component 1 for repair, for example, by mechanically or chemically removing any coatings, such as metallic and/or ceramic coatings, from component 1 (1005).

In this exemplary step, and because turbine engine components typically have one or more coatings that protect the component and/or the underlying substrate during operation, it may be necessary to remove those coatings in order to repair the damaged component. Examples of types of mechanical removal processes may include removal by sandblasting, sanding, and/or shot blasting. The chemical removal process may include removal, for example, by chemical stripping and/or etching.

After removing any coating, the method for preparing the component 1 may further comprise a cleaning process, for example by Fluoride Ion Cleaning (FIC) or similar process, to remove any oxides, for example from cracks in the component 1. It will be appreciated that in the case of a tight crack, such as a very tight crack, the tight crack may be opened using a carbide burr tool or a Dremel cutting wheel before undergoing a cleaning process.

Upon completion of the cleaning process, or alternatively, if cleaning is not required, the method 1000 may include the step of placing the component into a heating system 100, such as a furnace, to undergo a heat treatment. Where the component is carried by the heating system 100, a first thermal treatment of the component 1 can be applied/initiated, and includes heating the component 1 to a first temperature for a specified or predetermined period of time (1010). The first temperature may be a temperature lower than a melting temperature of grain boundaries to prevent eutectic melting of the grain boundaries. For example, in embodiments where grain boundary melting would otherwise occur at 1265 ℃, for example, the first temperature may be approximately 98% to 98.5% of the melting temperature 1265 ℃, such as 1245 ℃. The first temperature should be high enough to reduce or dissolve at least some of the eutectic without causing eutectic melting of the grain boundaries. The first temperature may also be sufficiently low to allow subsequent heat treatments at temperatures above the first temperature and below temperatures that would otherwise cause undesirable grain boundary eutectic melting.

Additionally or alternatively, the first temperature may be, for example, a temperature above a solution treatment temperature (solution treatment temperature) of a newly manufactured (as-cast) portion of the component subjected to the heat treatment. For example, in embodiments where the component includes CM 247, the Solution Treatment Temperature (STT) may be 1232 ℃ for a freshly manufactured as-cast component. In the case of a 1232 ℃ STT, this first temperature may be performed at 1242 ℃, which represents an increase of about 10 ℃ above the freshly manufactured STT. It should be understood that this 10 ℃ increase may depend on the type of superalloy material present, and that temperature increases above STT 10-30 ℃ are possible during heat treatment of the damaged part as long as undesirable grain boundary eutectic melting is not caused. Also, the first (or subsequent heat treatment) temperature should be high enough to dissolve at least some portion of the grain boundary eutectic without causing any melting of the grain boundaries.

With continued reference to the figures and the method 1000, heating the component to the first temperature may be gradual, i.e., slow, as compared to the rapid heating applied during conventional brazing operations. That is, the component may be slowly heated to the first temperature (slow heating) during the heat treatment because the slow heating helps prevent melting of the grain boundary eutectic compound while allowing time for the eutectic to dissolve. An example of slow heating may include heating the component to the first temperature at a rate of 2-5 ℃/minute (slow heating rate).

Additionally or alternatively, and since slow heating from an initial temperature, e.g., room temperature, to a first temperature may require an excessive amount of time, a combination of heating techniques (speeds), e.g., slow and accelerated (e.g., rapid) heating, may be used to reach the first temperature or any subsequent temperature during thermal processing. In this embodiment, i.e. where slow heating may be combined with accelerated heating, the component may be initially heated to, for example, 1100 ℃ by rapid heating and then slowly heated to the first temperature, for example for an additional 145 ℃. Since rapid heating to, for example, the first temperature may result in eutectic melting of the grain boundaries, slow heating must be employed after rapid heating to reach the first temperature. Rapid heating to the first temperature during heat treatment should be avoided because a rapid increase in temperature beyond any threshold as described herein can result in eutectic melting of the grain boundaries. Therefore, it is preferred to utilize rapid heating during the heat treatment stage before slow heating, and this rapid heating should be used to raise the temperature to about 100 ℃ below the first temperature. For example, in an embodiment where the first temperature is 1245 ℃, the rapid heating should continue to about 1145 ℃, which is 100 ℃ below the first temperature. It should also be appreciated that in further embodiments, rapid heating above the 100 ℃ threshold may be utilized, depending on the superalloy material and/or other considerations, so long as grain boundary eutectics are not induced during the rapid heating phase.

With continued reference to the figures, once the first temperature is reached, the first temperature should be maintained, e.g., constant, for about one to two hours during the first heat treatment. It should be understood that minor changes in temperature may not negatively affect grain boundaries when the first temperature or any temperature is held for a specified period of time, as long as the difference in temperature is nominal and consistent with any criteria for determining the first temperature.

For example, the specified or predetermined period of time to maintain the first temperature during the first thermal treatment may be between thirty minutes and four hours, depending on one or more of eutectic compound size, substrate material, or other factors. That is, more or less time may be required. In embodiments where the first temperature is about 1245 ℃, the time period may preferably be between forty-five minutes and three hours, or more preferably between one hour and two hours.

Slowly heating to the first temperature and holding at that temperature for a predetermined period of time allows the grain boundary eutectic to dissolve without melting. One example of such a grain boundary eutectic reduction is illustrated in the embodiment of fig. 4, which shows the damaged part 1 after a first heat treatment, for example at about 1245 ℃ for about two hours, which causes the grain boundary eutectic portion to dissolve and shrink.

After the heat treatment of the component 1, the component 1 is allowed to cool to, for example, room temperature (1015). The components may be allowed to cool naturally, i.e., without assistance from any cooling system or other means, or the cooling of the components may be by cooling system 130 or any means known in the art for cooling components carried by a furnace. It should be understood that natural cooling to room temperature may be achieved, for example, by reducing the temperature of heating system 100 or the temperature within heating system 100 to room temperature, or by reducing the temperature of component 1 to room temperature. To determine the current temperature of the component or within the furnace, one or more sensor assemblies, laser reading systems, or thermometers may be operatively connected to or used within the furnace to determine the current temperature.

With continued reference to the figures, upon cooling to room temperature, the method 1000 may further include a second heat treatment by heating the component 1 to a second temperature for a second period of time (1020). It should be understood that once the component 1 has been cooled to room temperature after the first heat treatment, or at any time during the cooling process when chosen with sound judgment, heating of the component to the second temperature may begin. It should also be understood that heating to the second temperature may also be by slow heating, or by any combination of heating techniques as described for the first heat treatment, for example, fast to slow heating as the temperature approaches the second temperature in order to further dissolve the grain boundary eutectic.

As shown in fig. 5, after the second heat treatment, the grain boundary eutectic of fig. 4 is further dissolved and shrunk. The means for determining the second temperature may be similar to the means for determining the first temperature above. For example, where grain boundary eutectic melting would otherwise occur at 1265 ℃, for example, the second temperature may be approximately 99% to 99.5% of the melting temperature 1265 ℃, such as 1255 ℃. It should be understood that the second temperature should be high enough to reduce or further dissolve the grain boundary eutectic size without causing any melting. Additionally or alternatively, the second temperature may be greater than the first temperature, e.g., by about 0.8% to 0.85%, which remains below a temperature that would otherwise result in undesirable grain boundary melting. It should also be understood that the heating rate, e.g., a slow heating rate, may be similar to the heating rate of the first heat treatment, e.g., a temperature increase of about 2-5 deg.C/minute.

Similar to the first time period, the second time period for the second temperature may be, for example, between thirty minutes and four hours, and depends on the remaining eutectic compound. After the second heat treatment, i.e. maintaining the second temperature for a second period of time, e.g. between one and two hours, the component 1 is allowed to cool down to e.g. room temperature by cooling system 130 or other cooling means known in the art (1015).

When the component 1 is cooled to room temperature after the second heat treatment, the component 1 may be ready for a braze repair operation, i.e. braze repair. The braze repair may be performed at any previous temperature for a third period of time, such as the first or second temperature that dissolves the grain boundary eutectic, such as 1255 ℃, or at a third temperature, which may be the grain boundary melting temperature, such as 1265 ℃, or higher than the previous temperatures of the first and second heat treatments (1030). In this embodiment, the heating rate during braze repair is different than the heating rate during heat treatment because the braze repair heating rate is as fast as possible to prevent corrosion, i.e., to prevent the braze material from dissolving the base metal components. An example of such a rapid heating rate may be an increase of about 10-30 deg.c/minute.

Once the desired holding temperature, i.e. the desired/achieved temperature for braze repair, e.g. the third temperature, is reached, the time period for braze repair may be shorter than both the first and second time periods, or may exceed any previous time period, depending on the extent of braze repair required to bring the component 1 to an operational state, i.e. a state in which the component has structural integrity back to the turbine engine. For example, the third time period may be between 0.1 and 12 hours, or preferably between thirty minutes and 12 hours. Because the third temperature may be a grain boundary eutectic melting temperature, such as 1265 ℃, less time may be required to complete the braze repair. It will be appreciated that rapid heating to brazing temperature ensures minimal chemical interaction between the component 1 and the brazing material and therefore reduces the amount of corrosion. It should also be appreciated that the rapid heating rate of the brazing operation does not result in melting of the base metal grain boundaries because at this temperature the base metal grain boundary eutectic has dissolved.

Additionally or alternatively, prior to the braze repair operation 1030, the method 1000 may also include a third heat treatment by repeating steps 1010 or 1020 for a specified period of time to further dissolve the grain boundary eutectic prior to braze repair. It should be understood that the third heat treatment may be performed at a temperature higher than either of the first and second temperatures, and provided that the temperature does not cause the grain boundaries to melt when applied. It should also be understood that, similar to the first and second heat treatments, reaching the third temperature may be by slow heating to the third temperature, or by a combination of rapid heating followed by slow heating, as described in any of the first and second heat treatments, e.g., rapid heating to a desired temperature below the third temperature, and then slow heating at, e.g., about 2-5 ℃/minute, and then holding the third temperature for about one to two hours before cooling to room temperature. Depending on the grain boundary eutectic after the third heat treatment, a subsequent heat treatment similar to any previous heat treatment may be required prior to the brazing operation, which may be at the temperature of any previous heat treatment or at a higher brazing temperature.

As can be seen in fig. 6, after the third heat treatment, similar to the first and second heat treatments, the grain boundary eutectic portions have further dissolved and are much smaller.

With continued reference to the figures, additionally or alternatively, the method 1000 may further include testing the component 1, such as by non-destructive testing or any other testing means known in the art, to determine whether the integrity of the component 1 has been compromised during the heat treatment and prior to resuming operation of the component 1. The test may be performed during cooling of the component 1 or at any time prior to heating the component 1 to the second, third or subsequent temperature to dissolve the grain boundary eutectic. Additionally or alternatively, and prior to resuming operation of the repaired component 1, the method 1000 may further include applying one or more coatings to the component 1. The coating may be applied by means known in the art for applying coatings to the component 1, for example, by spraying, vapor deposition, and the like.

While specific embodiments have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. For example, elements described in association with different embodiments may be combined. Accordingly, the particular arrangements disclosed are meant to be illustrative only and should not be construed as limiting the scope of the claims or the disclosure, which is to be given the full breadth of the appended claims and any and all equivalents thereof. It should be noted that the term "comprising" does not exclude other elements or steps and the use of the words "a", "an" or "an" does not exclude a plurality.