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  Method for making molybdenum parts using metal injection moldingUSPTO Application #: 20080075619Title: Method for making molybdenum parts using metal injection molding Abstract: Embodiments of a method for making molybdenum parts using metal injection molding are disclosed. In general, molybdenum powder is mixed or blended with a binder to form a feedstock, which is injection molded to form a green-state part. The green-state part is then sintered, such as by heating the part in a furnace for a predetermined period of time to effect consolidation and densification of the part. Desirably, the green-state part can be debound to remove at least a portion of the binder prior to sintering. In exemplary embodiments, sintering produces the final molybdenum article, and therefore the process does not require, but optionally may include, further processing of the sintered part, such as machining, cold-working, and/or hot-working. (end of abstract)
Agent: - , USPTO Applicaton #: 20080075619 - Class: 419 36 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080075619. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD [0001]The present invention concerns embodiments of a method for making molybdenum parts or shapes using metal injection molding. BACKGROUND [0002]Molybdenum parts, such as may be used in semiconductor devices or aerospace structures, are difficult to manufacture using conventional furnace melting techniques because of the high melting temperature of the element. Typically, molybdenum parts instead are made using powder metallurgy. A typical conventional manufacturing process involves several steps including forming a green-state part by powder cold compaction, sintering the green-state part, and employing metal-working techniques such as swaging, rolling, or drawing to make sheets, rods, bars or wires. The semi-finished parts are then further processed such as by machining, hot-working, and/or cold-working to form parts having complex three-dimensional shapes; that is, shapes other than the common sheet, rod, bar, or wire. As can be appreciated, this process is complicated and the use of machining often makes such processing uneconomical. SUMMARY [0003]The present disclosure concerns embodiments of a method for making molybdenum parts using metal injection molding. In general, molybdenum powder is mixed or blended with a binder to form a feedstock, which is injection molded to form a green-state part. The green-state part is then sintered, such as by heating the part in a furnace for a predetermined period of time to effect consolidation and densification of the part. Desirably, the green-state part can be debound to remove at least a portion of the binder prior to sintering. In exemplary embodiments, sintering produces the final molybdenum article, and therefore the process does not require further processing of the sintered part, such as machining, cold-working, and/or hot-working. Advantageously, the process can be used to form molybdenum parts having complex three-dimensional shapes more easily and is more economical than known processes. The process also can be used to form molybdenum alloy parts. [0004]In one representative embodiment, a method for making a molybdenum part comprises injection molding a feedstock to form an unsintered part. The feedstock comprises molybdenum powder and at least 45% by volume of a binder. The method further includes sintering the unsintered part. [0005]In another representative embodiment, a method for making a molybdenum part comprises injection molding a feedstock to form a green-state part, wherein the feedstock comprises molybdenum powder and at least one binder. The method further comprises debinding the green-state part to remove at least 40% of the binder to form a brown-state part. The brown-state part is then sintered at a peak temperature of no greater than about 3000.degree. F. [0006]In another representative embodiment, a method for making a molybdenum part comprises injection molding a feedstock to form an unsintered part, wherein the feedstock comprising molybdenum powder and at least one binder. The molybdenum powder desirably has a particle size ranging between about 0.1 micron and about 4 microns, and more desirably in the range of about 0.1 micron to about 0.5 micron. The method further includes sintering the unsintered part. [0007]In another representative embodiment, a method for making a molybdenum part comprises forming a feedstock by mixing a metal powder and a binder, and heating the mixture to a temperature sufficient to cause the binder to melt. The metal powder consists of molybdenum and has a particle size of no greater than about 5 microns, and the binder comprises at least 60% by volume of the feedstock. The feedstock is injection molded to form an unsintered part, which is then placed on an inner surface of a first setter. The inner surface of the setter is generally contoured to the shape of an adjacent surface of the part in contact with the inner surface. The first setter can be formed from a feedstock formed from molybdenum powder and a binder, which can be the same feedstock used to form the unsintered part. The unsintered part can be debound such as by placing the part (supported on the first setter) in a bath of at least one solvent. After the debinding step, a second setter is placed on the debound part so as to sandwich the part between the first and second setters. The second setter, like the first setter, also can be formed from a feedstock formed from molybdenum powder and a binder, which can be the same feedstock used to form the unsintered part. Finally, the debound part is sintered, such as by placing the part, along with the setters, in a sintering furnace for a predetermined period of time. The setters can be formed by any suitable method(s), such as metal injection molding. [0008]The foregoing and other features and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS [0009]FIG. 1 is a flowchart illustrating a method for making a molybdenum part using metal injection molding, according to one embodiment. [0010]FIG. 2 is a perspective view of one example of a molybdenum part that was formed by metal injection molding. [0011]FIG. 3 is a perspective view of another example of a molybdenum part that can be formed by metal injection molding. [0012]FIG. 4 is a perspective view of first and second setters that can be used to maintain the shape of the part shown in FIG. 3 during debinding and/or sintering of the part. DETAILED DESCRIPTION [0013]As used herein, the singular forms "a," "an," and "the" refer to one or more than one, unless the context clearly dictates otherwise. [0014]As used herein, the term "includes" means "comprises." For example, a device that includes or comprises A and B contains A and B but may optionally contain C or other components other than A and B. A device that includes or comprises A or B may contain A or B or A and B, and optionally one or more other components such as C. [0015]FIG. 1 shows a flowchart, indicated generally at 10, that illustrates a method for making a molybdenum part using metal injection molding, according to one embodiment. As shown, the method in exemplary embodiments generally includes forming a feedstock from a metal powder comprising molybdenum and at least one binder (indicated at 12), forming a green-state part (indicated at 14), optionally debinding the green-state part to form a brown-state part (indicated at 16), and sintering the brown-state or green-state part (indicated at 18). The metal powder optionally may include other metals or metal alloys. [0016]The part can have any of various complex three-dimensional shapes, which can include apertures, curves, recesses and/or other features that are not easily and readily formed using conventional manufacturing processes. FIGS. 2 and 3 show two examples of molybdenum parts indicated at 50 (FIG. 2) and 60 (FIG. 3), respectively, that can be made using metal injection molding. [0017]The metal powder can be manufactured using conventional techniques. The molybdenum powder desirably has a relatively small particle size, such as about 5 microns or less. In one specific implementation, the molybdenum powder has a particle size in the range of from about 0.1 to about 0.5 micron. In another implementation, the molybdenum powder has a particle size in the range of from about 3 to about 5 microns. In yet another implementation, the molybdenum powder comprises a mixture of at least two molybdenum powders having different particle sizes, such as a first powder having a particle size of about 0.1 to 0.5 micron and a second molybdenum powder having a particle size of about 3 to about 5 microns. The composition of the powder mix can be, for example, about 10-90% by volume of the 0.1-0.5 micron powder and about 90-10% by volume of the 3-5 micron powder. [0018]Any suitable binder can be used to form the feedstock. For example, the binder generally can comprise a plasticizer, an oil, or combinations thereof. Also, various water-soluble binders can be used. In certain embodiments, the binder comprises a plasticizer, a strengthener, a compatibilizer for the plasticizer and strengthener, and a surfactant. Without limitation, examples of plasticizers include paraffin wax, carnauba wax, polyethylene wax, or microcrystalline wax; examples of strengtheners include polypropylene, polystyrene, and polyacetal; examples compatibilizers include styrene-butadiene block copolymer (e.g., Kraton.RTM. commercially available from Shell) and ethyl vinyl acetate copolymer; and examples of surfactants include stearic acid, and zinc stearate. [0019]In one embodiment, a binder typically has a composition in weight percent of about 45% to 55% plasticizer, 45% to 55% strengthener, 3% to 6% compatibilizer, and 0.25% to 0.5% surfactant. A particular working embodiment comprised 48.5% paraffin wax, 48.5% polypropylene, 3% styrene-butadiene, and 0.25% stearic acid being a specific example. Continue reading... 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