Hot pressing of ceramic and metal powders has been used to produce a wide variety of advanced ceramics and metals that require high density and high strength. Hot pressing operations supply thermal energy under high pressure that is needed to transform powder materials into a wide variety of commodities and end-use consumer products. If the external pressure is uniaxially applied from top and bottom, then it is referred to as uniaxial hot pressing. Unfortunately, conventional uniaxial hot pressing technology can only produce parts with simple geometric shapes, such as discs, cylinders, cubes, rectangular blocks because it only provides the unidirectional pressing (e.g., up and down) without lateral (e.g., side) pressing. If conventional uniaxial hot pressing technology is used to make complicated shapes, the uniaxial hot pressed complicated shape results in cracking, non-uniform density or low density area due to the non-uniform stress distribution by the solid graphite punch. The major reason for these issues is because the solid graphite punch used in uniaxial hot pressing is rigid. The rigid graphite punch is uniaxially pressed, therefore it causes non-uniform applied stress at various locations.
Although hot-isostatic-pressing had been developed to isostatically hot press ceramic or metal powders, it relies on gas pressure instead of solid graphite media. Furthermore, hot-isostatic-pressing using gas pressure can only be applied to consolidated parts with closed pore structures. If raw powder or parts with open pores are hot-isostatic-pressed, the high pressure gas penetrates into the open pores and reaches equilibrium with the external applied gas pressure. When this equilibrium is reached, there is no external pressure to close the pores. To overcome this open pore issue, some researchers have used a metal can to enclose the raw powder or the part with open pore followed by a gas hot-isostatic-pressing. The metal can serve to the close barrier so that the external gas pressure can be applied to the metal, which then transmits the pressure to the part inside the metal can to close the pores of the powder or part during gas hot-isostatic-pressing. Some researchers have also buried the raw powder or open pore part with some ceramic or metal powder to assist the metal can in transmitting the gas pressure. Unfortunately, for hot-isostatic-pressing at very high temperatures, metals with higher melting points must be used. Metals with higher melting points are very brittle and cannot be deformed easily (e.g., Zirconium, Vanadium, Hafnium, Technetium, Boron, Niobium, Molybdenum, Tantalum, Tungsten). Other metals with higher melting point are precious metals and are extremely expensive (e.g., including Rhodium, Ruthenium, Iridium, Osmium, and Rhenium).
The inventors have identified a number of deficiencies and problems associated with existing hot pressing systems and methodologies. Through applied effort, ingenuity, and innovation, many of these identified problems have been solved by developing solutions that are included in embodiments of the present disclosure, many examples of which are described in detail herein.
Embodiments herein are directed to uniaxial hot pressing using graphite flake or hexagonal boron nitride to achieve a pseudo-isostatic-hot-pressing. Embodiments herein minimize the energy consumption and material waste caused by the extensive machining of a simple blank shape. Embodiments herein further provide an advanced manufacturing technology that can deliver higher quality components with a faster production rate.
Embodiments provide for a method of manufacturing a part. In example embodiments, a method includes positioning a material within a cavity of a die, positioning solid lubricant within the cavity of the die between a surface of a plunging component and the material, and uniaxially applying pressure to the material with the plunging component via the solid lubricant until the material forms a desired shape.
The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.
Having thus described the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Various embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, the disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. The term “or” is used herein in both the alternative and conjunctive sense, unless otherwise indicated. The terms “illustrative” and “exemplary” are used to be examples with no indication of quality level. Like numbers refer to like elements throughout.
To avoid using gas hot-isostatic-pressing and to improve the stress distribution during uniaxial hot pressing, embodiments herein use graphite flake or hexagonal boron nitride powder to replace the solid graphite punch used in conventional hot pressing. The graphite flakes or hexagonal boron nitrides (e.g., or other appropriate solid lubricant) can easily slide relative to each other enabling the redistribution or substantial uniform distribution of stress from high-pressure areas to low-pressure areas. The resulting substantially uniform pressure is very similar to an isostatic pressing. Hence, embodiments herein may be referred to as pseudo-isostatic-pressing that can produce a revolutionary breakthrough to the ceramic and metal industries for making complicated near-net-shape. This near-net-shape pseudo-isostatic-hot-pressing technology enables production of high density parts with improved density distribution throughout the whole part compared to that of parts produced using a solid rigid graphite punch. The near-net-shape technology can minimize the tedious and energy intensive machining work, which can save machining time and reduce footprint. By minimizing the machining work, the production rate can be increased while minimizing waste generation. This may save energy and resources (e.g., diamond grinding wheels). while reducing the rejection rate of parts thereby increasing the production yield.
Embodiments herein are directed to uniaxial hot pressing using graphite flake or hexagonal boron nitride to achieve a pseudo-isostatic-hot-pressing result. That is, embodiments herein achieve results akin to those that may otherwise only be achievable using hot-isostatic-pressing, by employing graphite flake or hexagonal boron nitride (e.g., a solid lubricant) in place of a rigid plunger in uniaxial hot pressing. Embodiments herein minimize energy consumption and material waste caused by the extensive machining of a simple blank shape. Embodiments herein further provide an advanced manufacturing technology that can deliver higher quality components with a faster production rate.
Embodiments herein provide for uniformly distributing force to form a part by using solid lubricant (e.g., graphite flake, hexagonal boron nitride, or the like) as the pressure transmitting material in order to form a part (e.g., a mortar, or the like) having a substantially uniform density. A part having a substantially uniform density is less likely to have cracks or defects caused by having been formed without uniformly distributed force applied to it.
Embodiments herein are described with reference to graphite flakes or hexagonal boron nitride, as examples of solid lubricants for use in embodiments herein. It will be appreciated that other solid lubricants may be used without departing from the scope of the present disclosure. Flakes, as described herein, may be associated with sizes ranging from 10 micron to 1 centimeter, although flakes of other sizes may be used without departing from the scope of the present disclosure.
This thin shell mortar 503 is a typical example and the same large hoop tensile stress can be developed for any other complicated shape such as a hollow cylinder, conical shape, rectangular cavity shape, crucible, pyramid, and the like. In order to advance to near-net-shape hot pressing technology, a transformational and revolutionary concept is needed to overcome the large hoop tension exertion on the surrounding material (e.g., 503) by the concaved/curved graphite top plunger (e.g., 501).
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After pseudo-hot-isostatic-pressing is completed, the graphite punch 605 can be removed followed by the graphite sleeve 603. The component 602 with graphite flake or hexagonal boron nitride 604 can then be ejected by pushing the graphite pin 606 upward from the bottom of the graphite die 602. The graphite flake or hexagonal boron nitride 604 can be easily removed by using a Dremel tool, sandblasting, or other appropriate means.
It will be appreciated that embodiments herein use a sleeve (e.g., graphite sleeve 603) to facilitate control of a width and/or thickness of one or more portions of the resulting part.
It will be appreciated that embodiments herein utilize a flat top plunger as shown in
Also shown in
It will be appreciated that embodiments herein utilize a graphite sleeve 603 that may be the same height as the flat end graphite plunger 605. Such a feature reduces manufacturing complexity as well as uncertainty with regard to placement of the graphite sleeve 603, the graphite plunger 605, and the placement of the components in relation to one another.
It will further be appreciated that embodiments herein may refer to the system and method depicted in
Example embodiments and variations are described below.
In various embodiments, a method of manufacturing a part includes positioning a material within a cavity of a die, positioning solid lubricant within the cavity of the die between a surface of a plunging component and the material, and uniaxially applying pressure to the material with the plunging component via the solid lubricant until the material forms a desired shape.
In some of these embodiments, the solid lubricant is configured to, responsive to the pressure, substantially uniformly distribute stress generated by the pressure to the material.
In some of these embodiments, the solid lubricant flexibly moves from high stress areas to low stress areas to substantially uniformly distribute stress generated by the pressure to the material.
In some of these embodiments, the die comprises rigid graphite. In some of these embodiments, the plunging component comprises rigid graphite. In some of these embodiments, the solid lubricant comprises one or more of ceramic powder, graphite flakes, boron nitride powder, or metal powder.
In some of these embodiments, the method further includes, prior to positioning the solid lubricant, forming the die into the desired shape such that the die defines the cavity with the desired shape, and loading a sleeve into the cavity of the die along an interior surface of the die that defines the cavity until a distal end of the sleeve contacts the material. In some of these embodiments, positioning the solid lubricant includes filling the cavity of the die with the solid lubricant up to a desired level, and inserting the plunging component into the cavity until the surface of the plunging component reaches an upper surface of the solid lubricant.
In some of these embodiments, the pressure is applied at a pressure level and a temperature level. In some of these embodiments, the temperature level is above 300° C. In some of these embodiments, the pressure level is greater than 10 Pound per Square Inch (PSI).
In some of these embodiments, the method further includes, upon completion of the material forming the desired shape, removing, using a pin embedded in a base of the cavity of the die, the material from the die. In some of these embodiments, the pin comprises a same material as the die. In some of these embodiments, a base surface of the base is flush with the pin when the pin is embedded in the base of the die. In some of these embodiments, removing the material, using the pin, comprises advancing the pin in a direction away from the base of the die.
In some of these embodiments, the sleeve comprises a first height and the plunging component comprises a second height. In some of these embodiments, the first height and second height are equal.
In some of these embodiments, the material comprises one or more of silicon carbide powder or aluminum nitride powder. In some of these embodiments, the solid lubricant comprises flakes. In some of these embodiments, the flakes comprise a size in a range of 1 micron to 1 centimeter. In some of these embodiments, the material comprises one or more of ceramic, metal, or composite materials. In some of these embodiments, the ceramic materials comprise one or more of oxide, carbide, nitride, oxynitride, oxycarbide, sulfide, phosphate, halide, or composite ceramic materials. In some of these embodiments, the metal materials comprise one or more of pure metal, alloy, or composite metal materials. In some of these embodiments, the material forming the desired shape results in one or more of a mortar, a bowl, a rectangular bowl, or a hollow pyramid.
In some embodiments, a system includes material positioned within a die, and a plunging component configured to uniaxially apply pressure to solid lubricant positioned between a surface of the plunging component and the material. In some of these embodiments, the system further includes a sleeve configured to facilitate control of one or more of a width or thickness of one or more portions of the material. In some of these embodiments, the material is configured to form a desired shape of the die responsive to the uniaxially applied pressure. In some of these embodiments, the solid lubricant is configured to, responsive to the uniaxially applied pressure, substantially uniformly distribute stress generated by the pressure to a first upper surface of the material.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
The present application claims priority to U.S. Provisional Application Ser. No. 63/252,346, titled “UNIAXIAL-HOT-PRESSING FOR MAKING NEAR-NET-SHAPE PARTS USING SOLID STRESS TRANSMITTING MEDIA,” filed Oct. 5, 2021, the contents of which are incorporated herein by reference in their entirety.
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| Number | Date | Country | |
|---|---|---|---|
| 63252346 | Oct 2021 | US |