Vacuum pressure transformation vessel and method of use

A method of forming a ceramic-metal composite part is described herein. The method includes maintaining molten metal in an interior of a housing in a liquefied state, the interior including a first chamber, a second chamber, and a port defined therebetween. The method further includes sealing the port such that the molten metal in the first chamber is maintained at a first liquid level, suspending a part at a height within the first chamber above the first liquid level, forming a pressure differential between the first chamber and the second chamber, unsealing the port such that molten metal from the second chamber flows into the first chamber, and resealing the port when the molten metal in the first chamber reaches a second liquid level such that the ceramic part is submerged in the molten metal.

BACKGROUND

The field of the present disclosure relates generally to ceramic-metal composites and, more specifically, to systems and methods for use in forming ceramic-metal composites.

Ceramic matrix composites (CMCs) are generally formed from a continuous reinforcing phase (i.e., ceramic and/or carbon fibers) embedded in a ceramic phase (i.e., a matrix material). Resulting CMC parts have desirable physical properties such as, but not limited to, high-temperature stability, high thermal-shock resistance, high hardness, high corrosion resistance, and/or nonmagnetic and nonconductive properties. However, CMC parts may also be brittle and susceptible to damage from high impact forces.

One known method of improving the durability of CMC parts is through a process referred to as transformation. Transformation generally includes infusing a CMC part with metal. At least some known transformation processes are performed in a furnace that contains a bath of molten metal in which the CMC part is submerged. For example, the furnace is filled with an amount of molten metal, and a transfer device attached to the furnace enables a CMC part to be loaded into the furnace. Once positioned within the furnace, the CMC part is positioned above the molten metal and a vacuum is drawn to facilitate removing air from the pores of the CMC part. The CMC part is then moved towards the bath by the transfer device for submersion within the molten metal. At least some known transfer devices include a plurality of independent moving parts that may result in formation of a leakage flow path from the furnace when the furnace is highly pressurized. In such cases, the effectiveness of the air removal step may be limited, thereby reducing the effectiveness of metal infusion into the CMC part.

BRIEF DESCRIPTION

In one aspect, a method of forming a ceramic-metal composite part is provided. The method includes maintaining molten metal in an interior of a housing in a liquefied state, the interior including a first chamber, a second chamber, and a port configured to provide flow communication between the first chamber and the second chamber. The method further includes sealing the port such that the molten metal in the first chamber is maintained at a first liquid level, suspending a ceramic part at a predetermined height within the first chamber above the first liquid level, forming a pressure differential between the first chamber and the second chamber such that a first pressure within the first chamber is less than a second pressure within the second chamber, unsealing the port such that molten metal from the second chamber flows into the first chamber, and resealing the port when the molten metal in the first chamber reaches a second liquid level, wherein the ceramic part is submerged in the molten metal at the second liquid level.

In another aspect, a vacuum pressure vessel is provided. The vessel includes a housing having an interior that includes a first chamber, a second chamber, and a port configured to provide selective flow communication between the first chamber and the second chamber. A part holder is selectively coupled to the housing. The part holder is configured to suspend a part at a predetermined height within the first chamber. A stopper is configured to selectively seal the port such that a liquid level in the first chamber and the second chamber is maintained when the port is sealed, and such that the liquid level in the first chamber and the second chamber is adjustable when the port is unsealed and a pressure differential is defined therebetween.

In yet another aspect, a vacuum pressure vessel system is provided. The system includes a vacuum pressure vessel that includes a housing having an interior that includes a first chamber, a second chamber, and a port configured to provide selective flow communication between the first chamber and the second chamber. The vessel includes a heating system configured to maintain molten metal in the interior in a liquefied state. A part holder is selectively coupled to the housing. The part holder is configured to suspend a part at a predetermined height within the first chamber. A stopper is configured to selectively seal the port such that a liquid level in the first chamber and the second chamber is maintained when the port is sealed, and such that the liquid level in the first chamber and the second chamber is adjustable when the port is unsealed and a pressure differential is defined therebetween. The system further includes a pressurization device in flow communication with the interior, wherein the pressurization device is configured to adjust a pressure within the first chamber and the second chamber. A controller is in communication with the stopper and the pressurization device, wherein the controller is configured to selectively actuate the stopper and the pressurization device for controlling operation of the vacuum pressure vessel system.

DETAILED DESCRIPTION

The embodiments described herein relate generally to systems and methods for use in forming ceramic-metal composites. More specifically, the systems described herein include a housing having a first chamber, a second chamber, and a port that provides flow communication therebetween. A stopper selectively seals the port to facilitate either maintaining or adjusting a liquid level of molten metal in the first chamber or the second chamber. For example, during operation, a part holder suspends a ceramic part within the first chamber above the liquid level therein. A pressure differential is then formed between the first chamber and the second chamber, and the port is unsealed such that molten metal from the second chambers flows into the first chamber. The port is resealed when the molten metal in the first chamber reaches a level in which the ceramic part is submerged in the molten metal. As such, the ceramic part is submerged in the molten metal without the use of a translating mechanical device, thus increasing the ability of the housing to be sealed and to effectively hold positive and negative pressures during a transformation cycle. As a result, a ceramic-metal composite part may be formed with improved mechanical properties.

As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “exemplary implementation” or “one implementation” of the present disclosure are not intended to be interpreted as excluding the existence of additional implementations that also incorporate the recited features.

FIG. 1is a schematic illustration of an exemplary vacuum pressure vessel system100. In the exemplary embodiment, system100includes a vacuum pressure vessel102including a housing104. Housing104includes an interior106including a first chamber108, a second chamber110, and a port112that provides selective flow communication between first chamber108and second chamber110. Interior106contains a bath114of molten metal therein. The molten metal may be formed from any metallic material that enables system100to function as described herein. An example molten metal includes, but is not limited to, molten aluminum.

A heating system116is included in interior106. Heating system116maintains bath114of molten metal in interior106in a liquefied state. For example, heating system116includes a first heater118positioned in first chamber108, and a second heater120positioned in second chamber110. First heater118and second heater120are submerged within bath114of molten metal to facilitate maintaining bath114in the liquefied state. In at least one example, heating system116is configured to maintain the molten metal at a temperature greater than approximately 1100 degrees Celsius.

In the exemplary embodiment, a part holder122is selectively coupled to housing104. That is, part holder122is configured to couple to housing104, and is also configured for removal from housing104. Part holder122suspends a part124at a predetermined height within first chamber108. For example, part holder122includes a lid126and a holding member128statically affixed (i.e., non-translatable) to lid126. Lid126is configured for coupling to housing104with an air tight seal such that housing104remains sealed during one or more pressurization cycles of a transformation cycle, as will be described in more detail below. For example, in one embodiment, part holder122further includes a gasket130coupled to lid126to facilitate sealing housing104when lid126is coupled thereto. Part holder122may also include a locking mechanism (not shown inFIG. 1) that interacts with a corresponding portion of housing104to maintain the air tight seal when the pressure within first chamber108is increased. Holding member128may be any mechanical device that enables part holder122to function as described herein. Example holding members include, but are not limited to, a porous basket or a hook. As such, holding member128enables bath114of molten metal to contact part124during a transformation cycle, as will be described in more detail below.

Part124may be fabricated from any material that enables system100to function as described herein. In the exemplary embodiment, part124is fabricated from a ceramic material such as, but not limited to, silicon carbide, aluminum oxide, silicon nitride, and/or aluminum nitride. As noted above, ceramic material is generally porous. As such, contacting part124with molten metal under predetermined process conditions results in formation of a ceramic-metal composite.

In the exemplary embodiment, vacuum pressure vessel102further includes a stopper132that is positionable for selectively sealing port112. Stopper132may be actuated manually by an operator, or may be actuated in an automated manner. For example, in one embodiment, stopper132includes a motor134and a sealing member136. Motor134is operable to facilitate translating sealing member136relative to motor134for selectively sealing port112. A liquid level in first chamber108and second chamber110is maintained when port112is sealed by stopper132. Alternatively, the liquid level in first chamber108and second chamber110is adjusted when port112is unsealed and a pressure differential is defined between first chamber108and second chamber110.

In one embodiment, sealing member136includes a plug head138formed at a distal end thereof. Plug head138is shaped to correspond to a shape of port112. For example, in the exemplary embodiment, port112includes a first opening140proximal to second chamber110, and a second opening142proximal to first chamber108. First opening140is sized larger than second opening142such that port112is formed with a tapered cross-sectional profile. Thus, plug head138has a tapered profile that enables plug head138to be securely seated within port112, and the tapered cross-sectional profile of port112facilitates controlling the flow of molten metal from second chamber110to first chamber108when plug head138is lifted to unseal port112.

In the exemplary embodiment, a first sensor144is coupled within first chamber108, and a second sensor146is coupled within second chamber110. First sensor144and second sensor146monitor the liquid levels in first chamber108and second chamber110. For example, first sensor144monitors the liquid level in first chamber108to ensure part124is submerged in bath114of molten metal during performance of a transformation cycle. First sensor144and second sensor146may be any contact or non-contact sensors that enable system100to function as described herein.

System100further includes a pressurization device148in flow communication with interior106. For example, housing104includes a first pressure port150and a second pressure port152defined therein. First pressure port150provides flow communication between pressurization device148and first chamber108, and is positioned to enable pressurization of first chamber108independently of second chamber110when port112is sealed. Second pressure port152provides flow communication between pressurization device148and second chamber110, and is positioned to enable pressurization of second chamber110independently of first chamber108when port112is sealed. Pressurization device148is capable of forming a negative pressure or a positive pressure within first chamber108and second chamber110. In addition, pressurization device148is capable of forming a negative pressure in first chamber108and a positive pressure in second chamber110simultaneously, or vice versa. As such, pressurization device148facilitates forming a pressure differential between first chamber108and second chamber110to facilitate selectively adjusting the liquid level heights in each chamber108and110. In at least one embodiment, pressurization device148is configured to create a negative pressure defined within a range between about 0 kPa and −200 kPa, between about −50 kPa and about −150 kPa, or approximately −100 kPa within first chamber108and/or second chamber110. Moreover, pressurization device148is configured to create a positive pressure defined within a range between about 100 kPa and about 1000 kPa, between about 500 kPa and about 1000 kPa, or approximately 700 kPa within first chamber108and/or second chamber110. Alternatively, the negative pressure and the positive pressure may be any pressures that enable system100to function as described herein.

System100further includes a controller154for automatically controlling operation of system100. Controller154includes a memory and a processor, comprising hardware and software, coupled to the memory for executing programmed instructions. The processor may include one or more processing units (e.g., in a multi-core configuration) and/or include a cryptographic accelerator (not shown). Controller154is programmable to perform one or more operations described herein by programming the memory and/or processor. For example, the processor may be programmed by encoding an operation as executable instructions and providing the executable instructions in the memory.

The processor may include, but is not limited to, a general purpose central processing unit (CPU), a microcontroller, a reduced instruction set computer (RISC) processor, an open media application platform (OMAP), an application specific integrated circuit (ASIC), a programmable logic circuit (PLC), and/or any other circuit or processor capable of executing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a computer-readable medium including, without limitation, a storage device and/or a memory device. Such instructions, when executed by the processor, cause the processor to perform at least a portion of the functions described herein. The above examples are exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the term processor.

The memory is one or more devices that enable information such as executable instructions and/or other data to be stored and retrieved. The memory may include one or more computer-readable media, such as, without limitation, dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), static random access memory (SRAM), a solid state disk, and/or a hard disk. The memory may be configured to store, without limitation, executable instructions, operating systems, applications, resources, installation scripts and/or any other type of data suitable for use with the methods and systems described herein.

Instructions for operating systems and applications are located in a functional form on non-transitory memory for execution by the processor to perform one or more of the processes described herein. These instructions in the different implementations may be embodied on different physical or tangible computer-readable media, such as a computer-readable media (not shown), which may include, without limitation, a flash drive and/or thumb drive. Further, instructions may be located in a functional form on non-transitory computer-readable media, which may include, without limitation, smart-media (SM) memory, compact flash (CF) memory, secure digital (SD) memory, memory stick (MS) memory, multimedia card (MMC) memory, embedded-multimedia card (e-MMC), and micro-drive memory. The computer-readable media may be selectively insertable and/or removable from controller154to permit access and/or execution by the processor. In an alternative implementation, the computer-readable media is not removable.

Controller154is coupled, either by wired or wirelessly connectivity, in communication with one or more of heating system116, stopper132, pressurization device148, first and second sensors144and146, and part holder122. In one implementation, controller154is autonomously operated when controlling the devices listed above for controlling operation of system100during performance of a transformation cycle. Alternatively, controller154is partially autonomous such that controller154can receive commands or other inputs from an operator during performance of the transformation cycle.

FIGS. 1-5are schematic illustrations of vacuum pressure vessel system100in various modes of operation. Referring toFIG. 1, system100is in a state of equilibrium. To reach the state of equilibrium, heating system116is operable to maintain bath114of molten metal in interior106of housing104in a liquefied state. In addition, pressurization device148is operable to form a pressure differential in interior106that facilitates adjusting a liquid level of molten metal in first chamber108to be at a first liquid level156. Stopper132seals port112to facilitate maintaining the molten metal at first liquid level156. Part124is loaded into part holder122, and part holder122is then positioned for coupling to housing104.

For example, referring toFIG. 2, lid126is coupled to housing104with an air tight seal. When lid126is coupled to housing104, part124is suspended at a predetermined height within first chamber108at a position above first liquid level156. As noted above, holding member128is statically affixed to lid126. As such, a length of holding member128is selected to facilitate suspending part124at the predetermined height within first chamber108.

Once housing104is sealed, pressurization device148is operable to form a pressure differential between first chamber108and second chamber110such that a first pressure within first chamber108is less than a second pressure within second chamber110. More specifically, pressurization device148facilitates drawing a vacuum in first chamber108, which is sealed by lid126and plug head138, and holding the vacuum in first chamber108for a predetermined duration. As such, air is removed from within first chamber108and from within the intermolecular structure of part124.

Referring toFIG. 3, port112is unsealed by removing plug head138therefrom such that molten metal from second chamber110flows into first chamber108. The molten metal flows from second chamber110into first chamber108by virtue of the pressure differential created by pressurization system when the vacuum is created in first chamber108. In some embodiments, an additional vacuum is drawn in first chamber108and/or second chamber110is pressurized to an elevated pressure to ensure the molten metal in first chamber108reaches a second liquid level158in which part124is submerged in the molten metal.

Referring toFIG. 4, port112is resealed when the molten metal reaches second liquid level158. Pressurization device148then pressurizes first chamber108to an elevated pressure after port112is resealed, and maintains first chamber108at the elevated pressure for a predetermined duration. As such, the molten metal infiltrates the intermolecular structure of part124. In one embodiment, pressurization device148pressurizes second chamber110when first chamber108is at the elevated pressure. For example, second chamber110may be pressurized to an elevated pressure that is substantially equal to the pressure within first chamber108, or may be pressurized such that a pressure differential between first chamber108and second chamber110is less than a predetermined threshold. As such, the pressure within interior106is substantially equalized to facilitate maintaining the seal across port112.

Referring toFIG. 5, port112is unsealed after the predetermined duration has elapsed. Prior to unsealing port112, pressurization device148is controlled to create a pressure differential between first chamber108and second chamber110such that the first pressure within first chamber108is greater than the second pressure within second chamber110. Once port112is unsealed, molten metal from first chamber108flows into second chamber110. Port112is then resealed when the molten metal in first chamber108returns to at least first liquid level156, as determined by either first sensor144or by second sensor146determining a liquid level in second chamber110. Alternatively, port112is resealed when the liquid level in first chamber108falls below the suspension height of part124(shown inFIG. 4). With the transformation cycle complete, part124is converted to a ceramic-metal composite part160. Part holder122may then be uncoupled from housing104and ceramic-metal composite part160removed therefrom.

FIG. 6is a flow diagram illustrating an exemplary method200of forming ceramic-metal composite part160using, for example, system100. Method200includes maintaining202molten metal in interior106of housing104in a liquefied state, sealing204port112such that the molten metal in first chamber108is maintained at a first liquid level, suspending206a ceramic part124at a predetermined height within first chamber108above the first liquid level, forming208a pressure differential between first chamber108and second chamber110such that a first pressure within first chamber108is less than a second pressure within second chamber110, unsealing210port112such that molten metal from second chamber110flows into first chamber108, and resealing212port112when the molten metal in first chamber108reaches a second liquid level, wherein ceramic part124is submerged in the molten metal at the second liquid level.