US20110048665A1

US20110048665A1 - Corrosion resistance for a leaching process

Info

Publication number: US20110048665A1
Application number: US12/853,205
Authority: US
Inventors: Max Eric Schlienger; Michael Christopher Maguire; Michael Dean Baldwin
Original assignee: Rolls Royce Corp
Current assignee: Rolls Royce Corp
Priority date: 2009-08-09
Filing date: 2010-08-09
Publication date: 2011-03-03
Also published as: EP2461922A4; WO2011019667A1; EP2461922A1

Abstract

A corrosion resistance system is disclosed that can be used in conjunction with a leaching device for removal of a mold from a cast component. The corrosion resistance system includes a container having a working fluid, such as a caustic fluid. A cast component and mold is placed within the container and a power supply is coupled to the component. During operation of the corrosion resistance system the cast component can be configured as an anode or as a cathode to provide for anodic or cathodic corrosion resistance. In one form the power supply is connected with an electrical conductor to the container and the cast component placed in electrical coupling with the container. An inert gas purge can supply an inert gas to the container. A vacuum pump can be used to remove gas from the container. Furthermore, an oxygen getter can be used in some embodiments.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Patent Application 61/232,454, filed Aug. 9, 2009, and is incorporated herein by reference.

TECHNICAL FIELD

The present invention generally relates to leaching devices used to remove a core/mold/shell from a cast component, and more particularly, but not exclusively, to corrosion resistance for the cast component during a leaching process.

BACKGROUND

Protecting cast component parts during a leaching process remains an area of interest. Some existing systems have various shortcomings relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology.

SUMMARY

One embodiment of the present invention is a unique ability to provide corrosion resistance to a cast component during a leaching process. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for providing corrosion resistance during a core/mold leaching process from a cast component part. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts one form of the present application.

FIG. 2 depicts an article having an object and a mold/core.

FIG. 3 depicts one form of the present application.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
In one aspect of the present application a mold used to receive a molten metal in an investment casting process is removed by a leaching process to reveal a cast article. The present application will be describe with reference to metals however it is contemplated herein as useful with elemental metals, alloys, superalloys and intermetallic materials unless specifically provided to the contrary. The mold can be made of a ceramic material and in one form is alumina. The leaching process utilizes a leaching fluid that interacts with and removes the mold material, but in so doing the leaching fluid in the vicinity of the ceramic being leached can become less reactive. To replenish its effectiveness, the leaching fluid can be boiled to sweep away the depleted solution and allow fresh leaching fluid to take its place. The leaching fluid can either be boiled through a conversion of liquid to vapor at, for example, a heat flux surface, or the leaching fluid can be placed in a superheated state where vapor can nucleate on a variety of surfaces within the system. Such a superheated state can be accomplished by, for example, suddenly dropping system pressure when the leaching fluid is at or near an equilibrium state.
An electric power supply is used to create an electrolytic cell which discourages corrosion or other attacks of the cast article from the leaching fluid. The power supply is used to provide a potential difference in the electrolytic cell in which the cast article can be configured as either an anode or a cathode. In some embodiments multiple cast articles can be used in the system, some of which are configured as an anode and others as a cathode. As will be described further below the power supply can be activated at any time and in one form in particular when the leaching fluid is being boiled to remove the ceramic mold.
With reference to FIG. 1, an electrolytic device 50 is shown that is capable of protecting an object from corrosion when the object is at least partially immersed in a working fluid 52. The object can take a variety of forms in various embodiments. To set forth just a few non-limiting examples, the object can be metallic, it can take the form of an alloy, and it can be produced using a casting process such as, but not limited to, investment casting. Other forms and variations of the object are also contemplated. In some applications the working fluid 52 can be a caustic fluid used as a leachant in an investment casting mold removal process, an example of which will be described further below. In one particular form the working fluid can be KOH. The working fluid 52 can also be NaOH, or mixtures of NaOH and KOH, among other possibilities, combinations, and mixtures. The electrolytic device 50 includes an anode 54 and a cathode 56 that can be driven to a potential difference by a power supply (not shown). Either the anode 54 or the cathode 56 can be coupled with such things as the object, a container that holds the working fluid 52, or with any other of a variety of structures. It will be appreciated, therefore, that any of the object, container, or other structures can themselves serve as the anode 54 or the cathode 56 of the electrolytic device 50. It will also be appreciated that whatever the ultimate form, either or both the anode 54 or the cathode 56 can be immersed completely into the working fluid or have a surface directly in contact with the working fluid 52. Some embodiments of the electrolytic device 50 are described further below.
FIG. 2 depicts one form of an article 58 that can be used with the electrolytic device 50. In the illustrated form the article 58 includes an object 60 coupled with a mold 62. The term mold as used herein can include a shell and/or a core, and each can be used interchangeably. The object 60 can be a cast metallic alloy and the mold 62 can be an alumina mold. The present application contemplates a wide variety of ceramic materials for the shell and/or core. Further, the shell and core can be formed of dissimilar material. The present application contemplates materials other than ceramics for use as the shell and/or core. Other variations either in the composition of the object 58 or the type of mold 62 are also contemplated herein. If made of a metallic alloy, the object 60 can be produced using a variety of techniques such as directional solidification, and can also take on crystal structures such as single crystal. Other forms of the object 60 are also contemplated. The metallic alloy can be a nickel based alloy, among other possibilities. In one form the mold 62 is produced using free-form fabrication techniques, such as but not limited to virtual pattern casting, laser stereolithography, and others. In one embodiment the mold 62 can be used to create a cast shape of the object 60 in the form of an aircraft gas turbine engine blade.
As used herein, the term “aircraft” includes, but is not limited to, helicopters, airplanes, unmanned space vehicles, fixed wing vehicles, variable wing vehicles, rotary wing vehicles, unmanned combat aerial vehicles, tailless aircraft, hover crafts, and other airborne and/or extraterrestrial (spacecraft) vehicles. Further, the present inventions are contemplated for utilization in other applications that may not be coupled with an aircraft such as, for example, industrial applications, power generation, pumping sets, naval propulsion, weapon systems, security systems, perimeter defense/security systems, and the like known to one of ordinary skill in the art.
Turning now to FIG. 3, one embodiment of a corrosion resistance system 64 is shown. The corrosion resistance system 64 includes a container 66 having the working fluid 52 and article 58 disposed within it. In one embodiment the container is made of nickel. In the illustrative form the corrosion resistance system 64 also includes an inert gas purge 68 operable to provide an inert gas within the container 66 above the working fluid 52, and a pump system 70 capable of withdrawing a gas, whether inert or otherwise, from within the container 66. Not all embodiments need have the one or both of the inert gas purge 68 or the pump system 70. The corrosion resistance system 64 includes an electrode 72 coupled with a power supply 75. In one form the electrode is metal which can made from platinum, among possible others. In the illustrative embodiment the electrode includes an end at least partially submerged within the working fluid 52.
In some embodiments of the instant application the corrosion resistance system 64 can be used in conjunction with a process to leach a ceramic core from the article 58. Such a leaching process can use heater 74 useful in providing a heat for a leaching process and to boil the working fluid 52 and leach the mold 62. Other mechanisms in addition or alternative to the heater 74 can also be used to heat and/or boil the working fluid 52. For example, a pressure of the working fluid 52 can be lowered to a point in which the working fluid 52 is at a superheated state thus encouraging nucleation and subsequent boiling of the working fluid 52. Mechanisms such as pumps can be used to change the pressure in the working fluid 52. For example, the pump system 70 can be used in some embodiments to not only withdraw a gas, whether inert or otherwise, from the container 66, but can also be used to provide a gas, whether inert or otherwise, into the container 66 to change the pressure of the working fluid 52. It will be appreciated, therefore, that either the inert gas purge 68 or the pump system 70 can be used to vary the pressure of the working fluid 52.
The power supply 75 can take the form of any variety of devices capable of providing and/or regulating a voltage or current. In one form the power supply 75 can be a DC power supply. In the illustrative embodiment the power supply is electrically coupled with the container 66. In one form the power supply 75 is further electrically coupled with the article 58 to provide either anodic or cathodic protection. In some embodiments the power supply 75 can be electrically coupled with the article 58 through a wire 76 extending between the article 58 and the container 66. Such a wire can be fixed within the container 66 by drilling and taping a hole. Alternatively and/or additionally, in still further embodiments the power supply 75 can be electrically coupled with the article 58 through a basket 78, such as a wire frame basket. The basket 78 can be electrically coupled with the power supply by contacting the container 66 or through an intervening conductor such as the wire 76.
If operated to provide anodic protection, a potential difference can be provided by the power supply 75 and the article 58 configured to be operated as an anode. As the potential difference is increased above a certain value the material of the article 58, and specifically the object 60, enters a passive region in which relatively little or no corrosion process is present.
If operated to provide cathodic protection, a potential difference can be provided by the power supply 75 and the article 58 configured to be operated as a cathode.
In some embodiments multiple articles 58 can be disposed within container 66 and the corrosion resistance system 64 can be operated to provide anodic or cathodic protection. In some embodiments, one or more articles 58 can be configured as an anode and one or more articles 58 can be configured as cathodes.
In still other embodiments, operating the corrosion resistance system 64 for an extended period of time can be useful in removing or mitigating oxide coatings on the inside of the container 66 and/or on the basket 78.
The inert gas purge 68 can include the devices depicted in FIG. 3 but not all embodiments need include each of the devices. The inert gas purge 68 can provide a gas to the container 66 at a variety of pressures and temperatures. The inert gas purge 68 can deliver a gas such as, but not limited to, argon.
The pump system 70 can include the devices depicted in FIG. 3 but not all embodiments need include each of the devices. The pump system can be used to extract a gas such as hydrogen from the container 66.
In some forms of the corrosion resistance system 64, an oxygen getter can be used to remove oxygen present within the container 66. Such an oxygen getter can take the form of, but not limited to, titanium, wood chips, etc.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

1. An apparatus comprising:

a vessel containing a ceramic leaching material;

a metallic alloy component coupled with a ceramic core and at least partially immersed within the ceramic leaching material;

a phase change transition device capable of boiling the ceramic leaching material to assist in removing the ceramic core from the metallic alloy component;

a power device in electrical communication with the metallic alloy component and having an anode and a cathode; and

wherein a protective electrolytic cell is formed that includes the ceramic leaching material and the metallic alloy component, the protective electrolytic cell discouraging material attack of the metallic alloy component.

2. The apparatus of claim 1, wherein the metallic alloy component is an anode of the electrolytic cell.

3. The apparatus of claim 1, wherein the metallic alloy component is a cathode of the electrolytic cell.

4. The apparatus of claim 1, wherein the ceramic core is part of a ceramic mold having a shell.

5. The apparatus of claim 1, which further includes an electric conductor connected between the vessel and the metallic alloy component.

6. The apparatus of claim 1, wherein the phase change transition device includes the capability to place the ceramic leaching material in a superheated state by varying the pressure of the ceramic leaching material.

7. An apparatus comprising:

a cast alloy structure having an casting core;

a vessel containing a caustic fluid used to leach the casting core and capable of transitioning between a liquid state and a vapor state, the state transition operable to sweep away depleted caustic fluid and replenish the caustic fluid in the vicinity of the casting core, the vessel in electrical conductive communication with the cast alloy structure;

an electrical power source capable of driving an electrochemical process and producing ions in the caustic fluid to alleviate a corrosion of the cast alloy structure.

8. The apparatus of claim 7, wherein the electric power source is driven to provide cathodic protection of the cast alloy structure.

9. The apparatus of claim 7, wherein the electric power source is driven to provide anodic protection of the cast alloy structure.

10. The apparatus of claim 7, wherein the cast alloy structure is made of a material with a relatively higher electrochemical potential than the vessel.

11. The apparatus of claim 7, which further includes an inert gas supply for delivering inert gas to the vessel and a gas withdrawal pump for extracting gas from the vessel.

12. The apparatus of claim 7, wherein the electrical power source is connected with an electrode in contact with the caustic fluid.

13. An apparatus comprising:

a metallic cast article coupled with a leachable ceramic device used to shape the metallic cast article;

a container having a leaching material within which the metallic cast article and leachable ceramic device is disposed;

means for protecting the metallic cast article during a leaching of the leachable ceramic device, the means in electrical communication with the metallic cast article via the container.

14. The apparatus of claim 13, wherein the means can be driving to a potential that places the metallic cast article in a passive range of an active-passive corrosion property.

15. The apparatus of claim 13, wherein during operation of the means, the means includes a potential that provides cathodic protection of the metallic cast article.

16. A method comprising:

dispensing a leaching material within a leaching vessel;

disposing a portion of a cast alloy part within the leaching vessel and exposing a ceramic container coupled with the cast alloy part to the leaching material;

facilitating a state transition of the leaching material from a liquid state to a vapor state;

creating an electrolytic device that includes the leaching material by attaching a first electrical conductor to a first terminal of a power supply and coupling a second electrical conductor to a second terminal of the power supply;

applying a potential difference between the first electrical conductor and the second electrical conductor; and

alleviating a corrosion process of the cast alloy part.

17. The method of claim 16, wherein the applying includes one of using the cast alloy part as an anode of the electrolytic device and using the cast alloy part as a cathode of the electrolytic device.

18. The method of claim 17, which further includes connecting an electrical conductor between the vessel and the cast alloy part.

19. The method of claim 16, which further includes superheating the leaching material.

20. The method of claim 16, which further includes changing the pressure in the leaching vessel.

21. The method of claim 20, wherein the changing includes one of providing an inert gas cover over the leaching material and evacuating a gas from the leaching vessel.