METHOD AND SYSTEM FOR PRODUCTION BASED ON METAL POWDER IN A GAS ATMOSPHERE LOW IN IMPURITIES - Patent application

Abstract

A metal powder based manufacturing system is provided that includes a sealed container forming a manufacturing chamber; a metal transformation / conversion unit contained within the manufacturing chamber that heats and transforms / converts a metal-based feedstock; an inert gas source operatively connected to the manufacturing chamber via an inert gas line and in gaseous communication with the manufacturing chamber to supply inert gas into the manufacturing chamber; and at least one gas purification unit in gaseous communication with the manufacturing chamber that purifies the inert gas to provide a purified inert gas having an oxygen partial pressure of less than about 100 ppb.

Description

[Technical Field]

[0001] The present invention relates generally to metal powder-based manufacturing systems having a manufacturing chamber with a low-impurity gas atmosphere, and more particularly to metal powder-based manufacturing systems, including metal-based powder manufacturing systems, powder metallurgy systems, and additive manufacturing systems, in which a metal-based feedstock is heated near or above its melting point and then cooled or solidified to create a desired final 3D shape or object. The present invention also relates to a metal powder-based manufacturing method in a low-impurity gas atmosphere. [Background technology]

[0002] There are various manufacturing methods in which metals are heated near or above their melting point and then cooled or solidified to create a desired final 3D shape or object, such as a single powder particle or a consolidated, molded bulk form. Advanced metal-based manufacturing methods include, for example, metal-based powder manufacturing, which produces metal-based powder particles from metal-based raw materials; powder metallurgy, which sinters metal-based powder particles into a consolidated, molded bulk form; and additive manufacturing (AM), which melts / sinters / agglomerates metal-based powder particles to create a consolidated, molded bulk form.

[0003] These manufacturing processes often utilize oxidation-sensitive metals such as Al and Ti; reaction-sensitive alloys such as, but not limited to, Zn, Cu, Fe, Li, Ni, Au, Pd, and Ag; and other metal alloys such as, but not limited to, steel or other iron alloys, SnPb, NdFeB, ZnPd, CoCr, brass-based alloys, and copper-based alloys. As a result, it is desirable to reduce or eliminate O, HO, CO, CO, H, and total hydrocarbons (THC) during the manufacturing process.

[0004] Typically, such manufacturing processes are carried out in an inert gas atmosphere, such as an argon- or helium-based atmosphere. However, even inert gases have impurity contents (oxygen, nitrogen, and other non-metallic elements). The impurity content of the inert gas can affect both the productivity and yield of the manufacturing process and the quality of the manufactured metal parts, whether in single metal-based powder particle or consolidated bulk form. There are multiple third-party definitions of inert processing that do not specify the level of inertness, and the term is generally imprecise. For example, manufacturing systems based on such heated metals operate at purity levels on the order of ppm (parts per million).

[0005] For example, during the production of metal-based powder particles for additive manufacturing or powder metallurgy, inert gas contaminants can induce oxide and / or inclusion formation, porosity, and water adsorption in the metal-based powder particles. Upon application of the raw material, the final part may contain oxide or nitride inclusions as well as porosity.

[0006] Also, impurities such as oxygen, nitrogen, and other non-metallic elements are effective surfactants and therefore affect the shape of the molten metal, including single particles (as in atomization) or the molten pool (as in additive manufacturing consolidation).

[0007] In view of this, there is a need for higher purity atmospheres in metal powder based manufacturing methods and systems, which can overcome or minimize some of the problems of the prior art discussed above. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention aims to solve the above-mentioned deficiencies. [Means for solving the problem]

[0009] According to a general aspect, a metal powder-based manufacturing system is provided, comprising: a sealed container forming a manufacturing chamber; a metal transformation / conversion unit contained within the manufacturing chamber and configured to heat and transform / transform a metal; an inert gas source operatively connected to the manufacturing chamber via an inert gas line and in gas communication with the manufacturing chamber to create an inert gas atmosphere within the manufacturing chamber; and at least one gas purification unit in gas communication with the manufacturing chamber to purify the inert gas to an oxygen partial pressure of less than about 100 ppb. In one embodiment, the metal powder-based manufacturing system further comprises a vacuum unit in gas communication with the manufacturing chamber to create a substantial vacuum within the manufacturing chamber.

[0010] In one embodiment, the metal transformation / conversion unit is selected from the group comprising an additive manufacturing unit, a metal-based powder manufacturing unit, a powder metallurgy unit, and a sintering furnace.

[0011] In one embodiment, the metal transformation / conversion unit is configured to melt the metal-based feedstock and solidify the molten metal into at least one final 3D part.

[0012] In one embodiment, the inert gas source includes at least one of an argon gas source, a nitrogen gas source, and a helium gas source.

[0013] In one embodiment, the metal powder-based manufacturing system further comprises a recirculation scrubbing system including a gas purification unit in gaseous communication with the manufacturing chamber via a closed-loop recirculation gas line.

[0014] In one embodiment, the metal powder-based manufacturing system further comprises a recirculation scrubbing system comprising at least one of the at least one gas purification unit in gaseous communication with the manufacturing chamber via a closed-loop recirculation gas line.

[0015] In one embodiment, at least one of the at least one gas purification unit is in gas communication with the fabrication chamber via the inert gas line, the gas purification unit being located downstream of the inert gas source and capable of purifying the inert gas provided by the inert gas source to an oxygen partial pressure of less than about 100 ppb before introduction into the fabrication chamber.

[0016] According to another general aspect, a method for transforming / converting metals is provided, the method including the steps of drawing gases from a fabrication chamber formed within a sealed vessel and including a metal transformation / conversion unit to form a substantial vacuum, supplying an inert gas to a gas purification unit to reduce the oxygen partial pressure to less than about 100 ppb, introducing the purified inert gas into the fabrication chamber under substantial vacuum, and heating metal in the metal transformation / conversion unit to transform / convert a metal-based feedstock into at least one final part.

[0017] According to another general aspect, a method for transforming / converting metals is provided, the method including the steps of monitoring an oxygen partial pressure within a fabrication chamber formed within a sealed vessel; continuously withdrawing gas from the fabrication chamber, purifying the withdrawn gas to reduce the oxygen partial pressure to less than about 100 ppb, and reinjecting the purified gas into the fabrication chamber; and thereafter heating the metal in a metal transformation / conversion unit contained within the fabrication chamber to transform / convert a metal-based feedstock into at least one final part.

[0018] According to yet another general aspect, a method for transforming / converting metals is provided, the method including the steps of withdrawing gas from a fabrication chamber formed within a sealed vessel and including a metal transformation / conversion unit; thereafter introducing an inert gas into the fabrication chamber; purifying the inert gas at least one of before and after introduction into the fabrication chamber to reduce the oxygen partial pressure to less than about 100 ppb to obtain a purified inert gas; and heating metal in the metal transformation / conversion unit to transform / convert a metal-based feedstock into at least one final part within the fabrication chamber containing the purified inert gas.

[0019] In one embodiment, the method further includes maintaining an oxygen partial pressure within the fabrication chamber at less than about 200 ppb. The method can further include controlling the oxygen partial pressure within the fabrication chamber by reusing a percentage of the gas volume within the fabrication chamber in a closed-loop recycle gas line that includes a recirculation scrubbing system. Controlling the oxygen partial pressure within the fabrication chamber can include monitoring the oxygen partial pressure within the fabrication chamber and adjusting the percentage of the gas volume circulating in the closed-loop recycle gas line.

[0020] The term "heated metal-based manufacturing method and system" is intended to encompass any manufacturing method and system in which a metal source (or metal feedstock) is heated to near or above its melting point and then cooled or solidified to produce a desired final 3D shape / object or at least one final part.

[0021] The metal source / metal-based feedstock can be in bulk or particulate form. The at least one final part can be a single powder particle or any other suitable final 3D part / object. The terms metal and metal-based are intended to encompass pure metals, alloys, or metals / alloys with other additives (e.g., but not limited to, binders, lubricants, ceramic nanoparticles, etc.).

[0022] According to another general aspect, there is provided a metal powder-based manufacturing system including: a sealed container forming a manufacturing chamber; a metal transformation / conversion unit contained within the manufacturing chamber and configured to heat and transform / convert a metal-based feedstock; an inert gas source operatively connected to the manufacturing chamber via an inert gas line and in gas communication with the manufacturing chamber to supply inert gas into the manufacturing chamber; and at least one gas purification unit in gas communication with the manufacturing chamber to purify the inert gas to provide a purified inert gas having an oxygen partial pressure of less than about 100 ppb.

[0023] In one embodiment, the metal powder based manufacturing system further includes a vacuum unit in gas communication with the manufacturing chamber to create a substantial vacuum within the manufacturing chamber.

[0024] In one embodiment, the metal transformation / conversion unit comprises at least one of an additive manufacturing unit, a metal-based powder production unit, a metal metallurgy unit, and a sintering furnace.

[0025] In one embodiment, the metal transformation / conversion unit is configured to melt the metal-based feedstock and solidify the molten metal into at least one final 3D part, wherein the at least one final 3D part can comprise a plurality of powder particles.

[0026] In one embodiment, the metal transformation / conversion unit is configured to heat a metal-based feedstock to a temperature below its melting point and cool the heated metal into at least one final 3D part.

[0027] In one embodiment, the inert gas source comprises at least one of an argon gas source, a nitrogen gas source, and a helium gas source.

[0028] In one embodiment, at least one of the at least one gas purification unit is attached to the inert gas line downstream of the inert gas source to purify the inert gas provided by the inert gas source into a purified inert gas having an oxygen partial pressure of less than about 100 ppb before introduction into the fabrication chamber. The metal powder-based manufacturing system can include a heating unit attached to the inert gas line downstream of the gas purification unit and configured to heat the purified inert gas before introduction into the fabrication chamber.

[0029] In one embodiment, the metal powder-based manufacturing system further includes a recirculation scrubbing system, the recirculation scrubbing system including a closed-loop recirculation gas line extending between a recirculation gas inlet and a recirculation gas outlet formed within the vessel and gaseously communicating with the manufacturing chamber; and at least one of the at least one gas purification units attached to the closed-loop recirculation gas line and gaseously communicating with the closed-loop recirculation gas line to purify the inert gas flowing therethrough into a purified inert gas having an oxygen partial pressure of less than about 100 ppb. The recirculation scrubbing system may further include a heat exchanger. The heat exchanger may be attached upstream of the at least one gas purification unit to cool the inert gas flowing therethrough. The recirculation scrubbing system may further include a heating unit attached downstream of the at least one gas purification unit to heat the inert gas flowing therethrough before being introduced into the manufacturing chamber. The recirculation scrubbing system may further include a gas compressor attached to the recirculation gas line. The metal powder-based manufacturing system may further include an oxygen-related sensor assembly that monitors an oxygen-related parameter in the manufacturing chamber, and a controller operatively connected to the gas compressor and the oxygen-related sensor assembly and that varies the speed of the gas compressor based on the oxygen-related parameter monitored by the oxygen-related sensor assembly. The oxygen-related sensor assembly may include an oxygen sensor assembly, and the oxygen-related parameter may be the oxygen partial pressure. The oxygen-related sensor assembly may include a ppm oxygen sensor and a ppb oxygen sensor, and the ppb oxygen sensor may be activated when the monitored oxygen content is below a ppm detection threshold.

[0030] In one embodiment, the purified inert gas has an oxygen partial pressure of less than about 50 ppb or less than about 20 ppb.

[0031] In one embodiment, the metal powder-based manufacturing system further includes a heating unit located within the manufacturing chamber and in conductive heat exchange with the manufacturing chamber to heat an inert gas contained within the manufacturing chamber.

[0032] In one embodiment, the at least one gas purification unit includes a gas-impermeable housing containing a sorbent material.

[0033] According to another general aspect, a method for transforming / converting metals is provided, the method including the steps of: supplying an inert gas to a gas purification unit to reduce the oxygen partial pressure therein to less than about 100 ppb to obtain a purified inert gas; introducing the purified inert gas into a manufacturing chamber formed within a sealed container and including a metal transformation / conversion unit; and heating a metal-based feedstock in the metal transformation / conversion unit to transform / convert the metal-based feedstock into at least one final part within the manufacturing chamber containing the purified inert gas.

[0034] In one embodiment, the method further comprises evacuating the fabrication chamber to a substantial vacuum prior to introducing purified inert gas into the fabrication chamber.

[0035] In one embodiment, the steps of supplying the inert gas and introducing the purified inert gas include: supplying the inert gas into a fabrication chamber; monitoring the oxygen partial pressure in the fabrication chamber; continuously withdrawing the inert gas from the fabrication chamber while the oxygen partial pressure in the fabrication chamber is greater than about 200 ppb, purifying the withdrawn inert gas to reduce its oxygen partial pressure to an oxygen partial pressure of less than about 100 ppb to obtain a purified inert gas; and then introducing the purified inert gas into the fabrication chamber.

[0036] In one embodiment, purified inert gas is introduced into the fabrication chamber under substantially vacuum via an inert gas line extending between an inert gas source and the fabrication chamber, to which the gas purification unit is attached, and in gaseous communication with the gas purification unit. The method can further include heating the purified inert gas prior to introduction into the fabrication chamber.

[0037] In one embodiment, heating the metal-based feedstock comprises melting the metal-based feedstock, hi another embodiment, heating the metal-based feedstock comprises heating the metal-based feedstock to a temperature below its melting point.

[0038] In one embodiment, supplying the inert gas includes supplying at least one of argon gas, nitrogen gas, and helium gas.

[0039] In one embodiment, the method further includes continuously withdrawing inert gas from the fabrication chamber while heating the metal-based feedstock; and purifying the withdrawn inert gas to reduce its oxygen partial pressure to less than about 100 ppb, and then introducing the purified inert gas into the fabrication chamber. The method may further include monitoring an oxygen-related parameter within the fabrication chamber; and adjusting the flow rate of the inert gas withdrawn from the fabrication chamber based on the monitored oxygen-related parameter within the fabrication chamber. In one embodiment, up to 100% (vol.) of the total gas volume within the fabrication chamber is withdrawn per minute. In one embodiment, the withdrawn inert gas is cooled before being purified. In one embodiment, the purified inert gas is heated before being introduced into the fabrication chamber.

[0040] In one embodiment, the purified inert gas exiting the gas purification unit has an oxygen partial pressure of less than about 50 ppb or less than about 20 ppb.

[0041] In one embodiment, the method further comprises heating an inert gas contained within the fabrication chamber.

[0042] In one embodiment, the method further includes the step of continuously evacuating gas contained within the manufacturing chamber, supplying an inert gas to a gas purification unit, and introducing the purified inert gas into the manufacturing chamber while heating the metal-based feedstock.

[0043] According to yet another general aspect, a method for transforming / converting metals is provided. The method includes the steps of: monitoring an oxygen-related parameter within a fabrication chamber formed within a sealed container; if the oxygen-related parameter within the fabrication chamber is greater than a predetermined oxygen threshold, continuously withdrawing an inert gas from the fabrication chamber while the oxygen-related parameter within the fabrication chamber is greater than the predetermined oxygen threshold, purifying the withdrawn inert gas to reduce its oxygen partial pressure to an oxygen partial pressure of less than about 100 ppb to obtain a purified inert gas, and introducing the purified inert gas into the fabrication chamber; and, if the oxygen-related parameter within the fabrication chamber is equal to or less than the predetermined oxygen threshold, heating a metal-based feedstock in a metal transformation / conversion unit contained within the fabrication chamber to transform / convert the metal-based feedstock into at least one final part. The oxygen-related parameter is the oxygen partial pressure, and the predetermined oxygen threshold can be about 200 ppb.

[0044] In one embodiment, the method includes drawing gas from the fabrication chamber to a substantial vacuum; and supplying an inert gas from an inert gas source into the fabrication chamber prior to continuously drawing the inert gas from the fabrication chamber. Supplying the inert gas into the fabrication chamber can further include supplying the inert gas to a gas purification unit to reduce its oxygen partial pressure to less than about 100 ppb before introducing the inert gas into the fabrication chamber. The method further includes heating the purified inert gas before introducing it into the fabrication chamber.

[0045] In one embodiment, heating the metal-based feedstock comprises melting the metal-based feedstock, hi another embodiment, heating the metal-based feedstock comprises heating the metal-based feedstock to a temperature below its melting point.

[0046] In one embodiment, supplying the inert gas includes supplying at least one of argon gas, nitrogen gas, and helium gas.

[0047] In one embodiment, the method further includes the steps of continuously withdrawing inert gas from the fabrication chamber while heating the metal-based feedstock; purifying the withdrawn inert gas to reduce its oxygen partial pressure to less than about 100 ppb; and then introducing the purified inert gas into the fabrication chamber. The method may further include adjusting the flow rate of the inert gas withdrawn from the fabrication chamber based on monitored oxygen-related parameters within the fabrication chamber. In one embodiment, the withdrawn inert gas is cooled before being purified. In one embodiment, the purified inert gas is heated before being introduced into the fabrication chamber.

[0048] In one embodiment, the purified inert gas exiting the gas purification unit has an oxygen partial pressure of less than about 50 ppb or less than about 20 ppb.

[0049] In one embodiment, the method further comprises heating an inert gas contained within the fabrication chamber.

[0050] In one embodiment, the method further includes the steps of continuously evacuating gas contained in the manufacturing chamber, supplying an inert gas to the gas purification unit, and introducing the purified inert gas into the manufacturing chamber while heating the metal-based feedstock.

[0051] According to yet another general aspect, there is provided another method for transforming / converting metals, the method including the steps of: introducing an inert gas into a fabrication chamber formed within a sealed container and including a metal transformation / conversion unit; purifying the inert gas at least one of before and after introduction into the fabrication chamber to reduce the oxygen partial pressure to less than about 100 ppb to obtain a purified inert gas; introducing the purified inert gas into the fabrication chamber; and heating a metal-based feedstock in the metal transformation / conversion unit to transform / convert the metal-based feedstock into at least one final part within the fabrication chamber containing the purified inert gas.

[0052] In one embodiment, the method further comprises evacuating gas from the fabrication chamber to a substantial vacuum before introducing an inert gas into the fabrication chamber.

[0053] In one embodiment, the method further includes monitoring an oxygen-related parameter within the fabrication chamber, and introducing purified inert gas into the fabrication chamber until the oxygen-related parameter within the fabrication chamber is below a predetermined oxygen threshold, where the oxygen-related parameter is the oxygen partial pressure and the predetermined oxygen threshold can be approximately 200 ppb.

[0054] In one embodiment, a step of purifying the inert gas occurs after introduction into the fabrication chamber; the step of purifying the inert gas includes the steps of sequentially withdrawing the inert gas from the fabrication chamber, purifying the withdrawn inert gas to reduce its oxygen partial pressure to an oxygen partial pressure of less than about 100 ppb, obtaining a purified inert gas, and then introducing the purified inert gas into the fabrication chamber.

[0055] In one embodiment, the step of purifying the inert gas occurs before introduction into the fabrication chamber via an inert gas line extending between an inert gas source and the fabrication chamber, having a gas purification unit attached thereto and in gaseous communication with the gas purification unit. The method may further include the step of heating the purified inert gas before introduction into the fabrication chamber.

[0056] In one embodiment, heating the metal-based feedstock comprises melting the metal-based feedstock, hi another embodiment, heating the metal-based feedstock comprises heating the metal-based feedstock to a temperature below its melting point.

[0057] In one embodiment, supplying the inert gas includes supplying at least one of argon gas, nitrogen gas, and helium gas.

[0058] In one embodiment, the method includes continuously withdrawing inert gas from the fabrication chamber while heating the metal-based feedstock; and purifying the withdrawn inert gas to reduce its oxygen partial pressure to less than about 100 ppb before introducing the purified inert gas into the fabrication chamber. The method further includes monitoring an oxygen-related parameter in the fabrication chamber; and adjusting the flow rate of the inert gas withdrawn from the fabrication chamber based on the monitored oxygen-related parameter in the fabrication chamber. In one embodiment, the withdrawn inert gas is cooled before being purified. In one embodiment, the purified inert gas is heated before being introduced into the fabrication chamber. In one embodiment, the purified inert gas exiting the gas purification unit has an oxygen partial pressure of less than about 50 ppb or less than about 20 ppb.

[0059] The method may further include heating an inert gas contained within the fabrication chamber.

[0060] In one embodiment, the method further includes the step of continuously evacuating gas contained in the manufacturing chamber, supplying an inert gas to the gas purification unit, and introducing the purified inert gas into the manufacturing chamber while heating the metal-based feedstock.

[0061] As used herein, the term "metal powder-based manufacturing methods and systems" is intended to encompass all manufacturing methods and systems that include metal powders as either a metal source (or metal feedstock) or a final part, and includes manufacturing methods and systems in which a metal-based powder is manufactured as a final part. The term also encompasses manufacturing methods and systems in which a metal-based powder as a metal source / metal-based feedstock is transformed / converted into a desired final 3D shape / object / part (i.e., final part), including powder metallurgy and additive manufacturing. The final 3D shape / object / part can be a single object / part or multiple single particles that together form a powder.

[0062] As used herein, the term "additive manufacturing" includes binder jetting, laser sintering, powder bed fusion bonding, directed energy deposition, material extrusion, and the like.

[0063] For purposes of this disclosure, "high purity" gas means a gas having individual contaminant levels of less than about 100 ppb (parts per billion). Also, when referring to oxygen partial pressure (or other contaminant partial pressure), it is understood that it may be measured directly, for example, via an oxygen sensor or oxygen sensor assembly, or indirectly from other variables from which the oxygen or contaminant level can be derived or estimated. [Brief explanation of the drawings]

[0064] [Figure 1] FIG. 1 is a block diagram of a metal powder-based manufacturing system according to a first embodiment. [Figure 2] FIG. 1 is a block diagram of a metal powder-based manufacturing system according to a second embodiment including a recirculating gas flow. DETAILED DESCRIPTION OF THE INVENTION

[0065] An embodiment of a metal powder-based manufacturing system 20 that can be used to generate or convert metal-based powders into bulkier 3D objects / parts (i.e., parts or objects larger than a single particle) by powder metallurgy or additive manufacturing is shown in FIG. 1. In the metal powder-based manufacturing system 20, a metal source (or feedstock) is heated to near or above its melting point and then cooled / solidified to create the desired final 3D shape or part. As previously mentioned, the final 3D shape or part can be a single object / part or multiple single metal-based particles that together form a powder (also referred to as a metal powder or metal-based powder).

[0066] The manufacturing system 20 includes a vessel 22 having walls 27 that define a manufacturing chamber 24. Within the manufacturing chamber 24 resides a metal transformation / conversion unit 26. The vessel 22 is sealed to prevent gas leakage and ingress through the walls 27. Thus, gas ingress and egress is possible only through specific gas inlets and ports, as will be described in more detail below. As will be described below, the interior of the manufacturing chamber 24 maintains a gas atmosphere low in impurities. The gas atmosphere within the manufacturing chamber 24 can be controlled or regulated, at least with respect to the impurity content.

[0067] Gaseous impurities (or contaminants) include at least one of oxygen, moisture, nitrogen, and other non-metallic elements such as carbon monoxide, hydrocarbons (including methane), etc., which interact with heated / molten metal and are detrimental to the properties of the final part. Here, gas purity refers to the content of impurities in a gaseous atmosphere. Gas purity can be determined in terms of the content of a specific impurity or the content of total impurities. For example, gas purity in terms of oxygen content is measured in terms of oxygen partial pressure. Gas purity can also be determined in terms of the content of total impurities relative to selected impurities (e.g., oxygen, moisture, and nitrogen).

[0068] The metal transformation / conversion unit 26 includes a metal-based powder production unit, a powder metallurgy unit, and / or an additive manufacturing unit, where a metal-based feedstock is heated to a temperature near or above its melting point and then cooled or solidified to produce a desired final 3D part, which can be a single powder particle or a solidified, molded bulk 3D form (or final 3D part / object). Thus, in the metal transformation / conversion unit 26, the metal-based feedstock is transformed / converted into other shapes in the presence or absence of additional elements such as added binders, lubricants, ceramic nanoparticles, etc.

[0069] The metal transformation / conversion unit 26 present in the sealed vessel 22 is a metal-based powder production unit configured to atomize metal into metal-based powder particles (also referred to as metal-based particles or powder particles). The particles can be considered as powder particles with an average diameter of about 10 μm to about 125 μm used in the field of powder metallurgy or powder-based additive manufacturing.

[0070] The metal-based powder production unit melts a metal-based raw material (or metal-based feedstock) and breaks the molten metal into fine droplets that then solidify into powder particles.

[0071] The metal transformation / conversion unit 26 present in the sealed container 22 may be a 3D printer that produces solidified bulk 3D forms. The 3D printer successively melts thin layers of metal-based powder to create the final 3D part. Additives such as binders can be added during the printing process.

[0072] The metal transformation / conversion unit 26 present in the sealed container 22 may also be a sintering furnace for heating the compacted metal-based powder to near its melting point to promote intra-particle diffusion and inter-particle bonding to obtain a solid mass (or final 3D part / object).

[0073] The manufacturing system 20 further includes one or more inert gas sources 28, such as argon, nitrogen, or helium, and one or more gas purification units 30 in gas communication with the manufacturing chamber 24 via an inert gas line 31. The gas supplied by the inert gas source 28 is purified in the purification units 30 to remove impurities before being injected into the manufacturing chamber 24. The manufacturing system 20 of FIG. 1 has two inert gas sources 28, each containing a different inert gas, and two gas purification units 30, each in gas communication with one of the inert gas sources 28. The two inert gas sources 28 and gas purification units 30 are similar, and only one set will be described below.

[0074] Gas purification unit 30 is located downstream of inert gas source 28 relative to fabrication chamber 24. Thus, inert gas line 31 includes a plurality of continuous inert gas conduits extending between the inert gas source and the purification units through which gas passes. For example, a first inert gas conduit exists between the inert gas source and gas purification unit 30.

[0075] Gas purification unit 30 purifies inert gas (nitrogen, argon, or other inert gases) from oxygen, moisture, carbon monoxide, hydrocarbons (including methane), and other contaminants. Gas purification unit 30 includes an impermeable housing with a port connected to an inert gas line. Appropriate filters, adsorbents (or metal getters), and catalysts are contained within the purification unit housing. For example, Entegris' GateKeeper® Inert Gas Purifiers, Pall's Gaskleen® II Purifier, NuPure Corporation's Eliminator®, and those disclosed in U.S. Patent 5,902,561, incorporated herein by reference, may be used.

[0076] The gas purification unit 30 operates at ambient (room) temperature and processes a continuous gas stream.

[0077] The adsorbent contained in the purification unit housing has a porous body and is composed at least in part of a transition metal and / or a zeolite. The adsorbent may include a powder of a reactive alloy.

[0078] The gas purity leaving purification unit 30 is less than about 100 ppb for at least one contaminant, but may be less than about 50 ppb, or less than about 10 ppb.

[0079] The manufacturing system 20 may further include a mass flow controller 33 downstream of and in communication with the gas purification unit 30. In the illustrated embodiment, each inert gas line 31 has its own mass flow controller 33. The mass flow controller 33 measures and controls the flow of gas in the inert gas line 31. The set point of the mass flow controller may be changed to adjust and control the flow rate of the inert gas entering the manufacturing chamber 24.

[0080] 1, the inert gas from the two mass flow controllers 33 is combined before entering the manufacturing chamber 24 of the vessel 22, reducing the number of gas inlets formed in the vessel wall 27 and reducing the possibility of gas leakage from the manufacturing chamber 24. A control valve 35 is provided on a single inert gas line 31 that extends downstream of the mass flow controllers 33 and communicates with the manufacturing chamber 24 of the vessel 22. The inert gas line 31 is connected to the vessel 22 via an inert gas inlet 32 ​​formed in the vessel wall 27.

[0081] 1 has two inert gas lines 31 extending side by side upstream of a control valve 35, each line having one inert gas source 28 and one gas purification unit. However, there may be a single inert gas line having one inert gas source 28 and one gas purification unit 30, or there may be more than one inert gas source 28 supplying gas to one gas purification unit 30 located downstream of one or more inert gas sources 28. For example, there may be a single inert gas line and only one mass flow controller 33 and control valve 35.

[0082] Two or more inert gas sources 28 and / or gas purification units 30 may be arranged in parallel or in series. When arranged in parallel, the inert gas conduits may be connected upstream or downstream of the gas purification units 30 (when there are fewer gas purification units 30 than inert gas sources 28). Each gas purification unit 30 may have an inert gas conduit connected to a respective inert gas inlet 32 ​​formed in the vessel wall 27, and the vessel 22 may have two or more inert gas inlets 32.

[0083] The manufacturing system 20 of FIG. 1 further includes a gas heating unit 70, such as an indirect heat exchanger, downstream of the control valve 35, i.e., between the control valve 35 and the inert gas inlet 32. The gas heating unit 70 can be provided, for example, in the inert gas line 31 upstream of the control valve 35. The gas heating unit 70 need not be present between the inert gas source 28 and the inert gas inlet 32. Thus, when activated, the gas heating unit 70 heats the purified inert gas before it enters the manufacturing chamber 24. The gas heating unit 70 may regulate and control the temperature of the inert gas entering the manufacturing chamber. The temperature of the inert gas before entering the manufacturing chamber 24 is referred to as the inert gas inlet temperature. The gas heating unit 70 includes a gas heater actuator operatively connected to a controller, which can be operatively connected to one or more temperature sensors provided in the inert gas line 31 and / or the manufacturing chamber 24. A liquid-to-gas or discontinuous (or intermittent) heat exchanger, such as a regenerative heat exchanger, may also be used.

[0084] In the embodiment of FIG. 1, a vacuum unit 34 , such as a vacuum pump, may be in gas communication with the fabrication chamber 24 via a vacuum gas line 36 fitted with a control valve 37 and a vacuum port 38 in the vessel wall 27 .

[0085] Also present in manufacturing system 20 is a monitoring assembly that is operatively connected to vessel 22 and includes a pressure sensor 39, a temperature sensor (153 in FIG. 2), and oxygen sensors 40a, 40b that monitor the pressure, temperature, and oxygen content, respectively, within manufacturing chamber 24. More or fewer sensors than those shown may be present in manufacturing system 20.

[0086] 1, pressure sensor 39 is a pressure sensor controller operatively connected in data communication with two mass flow controllers 33. Data communication is indicated by dashed lines. Thus, the flow rate of inert gas entering fabrication chamber 24 is adjusted and controlled based on pressure data monitored in fabrication chamber 24 by pressure sensor 39.

[0087] An oxygen sensor assembly 40 operatively connected to the vessel 22 for monitoring the oxygen content within the fabrication chamber 24 includes two oxygen sensors. The oxygen sensor assembly may include a first oxygen sensor 40a that measures a relatively high oxygen content (units: ppm) and a second oxygen sensor 40b that measures a relatively low oxygen content (units: ppb). To protect the low-content oxygen sensor 40b, this sensor is activated only when the oxygen content is below the ppm detection threshold. A valve 41 is attached to a gas line 43 between the oxygen sensor assembly 40 and the fabrication chamber 24. As will be explained in more detail below, the valve 41 is closed when the vacuum unit 34 operates to evacuate the fabrication chamber 24 and is opened when the metal deformation / conversion unit 26 operates.

[0088] In other manufacturing systems (not shown), there may be only one oxygen sensor, for example, low-content oxygen sensor 40b, that monitors oxygen content down to ppb levels.

[0089] The oxygen sensor assembly may be substituted for or used in conjunction with other sensor assemblies capable of deriving information related to the oxygen content within the fabrication chamber 24. For example, the oxygen content may be derived or inferred from a nitrogen sensor assembly and / or a moisture sensor assembly and / or a carbon dioxide sensor assembly. All such sensor assemblies may be used in place of or in conjunction with the oxygen sensor assembly.

[0090] 1 includes a safety valve 45 and a chamber refilling valve 47, both of which are operatively connected to the vessel 22 and communicate with the manufacturing chamber 24. The refill valve 47 is closed when the metal transformation / conversion unit 26 present in the sealed vessel 22 is activated. At the end of the metal transformation / conversion operation, the refill valve 47 is opened to refill the manufacturing chamber 24 with ambient air.

[0091] In embodiments in which purified inert gas is continuously supplied to fabrication chamber 24, refill valve 47 is at least partially open, thereby allowing fabrication chamber 24 to gradually vent gas at a meterable rate to the ambient atmosphere through valve 47. In such embodiments, the pressure within fabrication chamber 24 should be maintained slightly above ambient pressure.

[0092] Although a heating unit 72 is present within the fabrication chamber 24 of the fabrication system 20 of FIG. 1 , the heating unit 72 may be located nearby, rather than within, the fabrication chamber 24. The heating unit 72, which may be a heat exchanger, heats the purified inert gas within the fabrication chamber 24 and the surrounding area. Like the gas heating unit 70, the heating unit 72 can regulate and control the temperature of the inert gas within the fabrication chamber 24. A gas heater actuator is operatively connected to a controller, which may be operatively connected to a temperature sensor that senses the gas temperature within the fabrication chamber 24. Alternatively, the heating unit need not be located within or near the fabrication chamber 24.

[0093] Another production system 120 of FIG. 2 includes a recirculating scrubbing system 142 and other features similar to production system 20.

[0094] The recycle scrubbing system 142 includes a closed-loop recycle gas line 146 having a recycle gas inlet 148 and a recycle gas outlet 149 formed in the vessel wall 127 and passing through the production chamber 124. Along the closed-loop recycle gas line 146 from the recycle gas inlet 148 to the recycle gas outlet 149 of the recycle scrubbing system 142 are, in order, a filter 150, a compressor 152, a heat exchanger 154 for cooling the gas circulating in the gas line 146, and a gas purification unit 156, which is similar to the gas purification units 30 and 130 described above. The recycle scrubbing system 142 generates a continuous gas stream that circulates within the closed-loop recycle gas line 146 and the gas purification unit 156. The heat exchanger 154 removes heat added to the gas circulating in the gas line 146 by compression in the compressor 152 and generated by the molten metal process within the production chamber 124.

[0095] Alternatively, at least one of the filter 150 and the heat exchanger 154 may be omitted.

[0096] A heating unit 174, such as a heat exchanger, is further present downstream of the gas purification unit 156 in the recirculation scrubbing system 142, i.e., between the gas purification unit 156 and the inert gas inlet 149. The gas heating unit 149 can be present at other locations along the gas line 146. Thus, the activated gas heating unit 174 heats the purified inert gas before it enters the production chamber 124. The gas heating unit 174 may adjust and control the temperature of the inert gas entering the production chamber 124. The gas heater actuator is operatively connected to a controller, which can be operatively connected to a temperature sensor provided inside the inert gas line 146 and / or the production chamber 124. The gas heating unit 174 need not be present.

[0097] The purpose of recirculation scrubbing system 142 is to eliminate or minimize the impurity content and continuously purify the gaseous atmosphere inside fabrication chamber 124 during the fabrication process. While the inert gas enters fabrication chamber 124 and is purified by gas purification unit 130, oxygen and other contaminants may diffuse and build up within fabrication chamber 124. Thus, recirculation scrubbing system 142 generates a recirculation gas stream, where the gas in fabrication chamber 124 is evacuated and purified before re-entering. By recirculation scrubbing system 142, the inert gas content of fabrication chamber 124 is continuously scrubbed from oxygen and other impurities that diffuse into fabrication chamber 124 of vessel 122.

[0098] Up to 100% (vol.) of the total gas volume per minute, i.e., the gas volume entering the production chamber 124, is recycled, exiting the production chamber 124 and sent to the gas purification unit 156 before returning to the production chamber 124. Alternatively, 1-50% (vol.), 5-20% (vol.), or 10-20% (vol.) of the total gas volume per minute may be recycled through the recirculation scrubbing system 142. The percentage of gas scrubbed through the recirculation scrubbing system 142 may vary proportionally to the readings obtained from the oxygen sensor assembly 140.

[0099] A controller (not shown) may be operatively connected to the oxygen-related sensor assembly, i.e., oxygen sensor assembly 140 capable of inducing oxygen content, and recycle scrubbing system 142. The speed of compressor 152 is varied in response to the data from oxygen sensor assembly 140 to adjust the recycled gas flow rate in closed-loop recycle gas line 146. An increase in the oxygen content in production chamber 124 increases the recycle gas flow rate, and vice versa.

[0100] Alternatively, the inert gas source 128 may be in direct gas communication with the fabrication chamber 124 without the gas purification unit 130, and the inert gas source 128 may directly fill the fabrication chamber 124 with unpurified inert gas. The unpurified inert gas may be purified by the gas purification unit 156 of the recirculation scrubbing system 142. Thus, prior to metal transformation / conversion in the fabrication chamber 124, the recirculation scrubbing system 142 may be activated to purify the inert gas within the fabrication chamber. The recirculation scrubbing system 142 may be activated until the contamination level of the gaseous atmosphere within the fabrication chamber 124 is below a predetermined threshold, such as an oxygen partial pressure of less than 100 ppb.

[0101] Like manufacturing system 20, manufacturing system 120 includes a monitoring assembly with multiple actuators and sensors, including a mass flow controller 133 gaseously coupled to inert gas source 128 and gas purification unit 130, a control valve 135 in inert gas line 131, a safety valve 145, a refill valve 147, and pressure sensor 139, temperature sensor 153, and oxygen sensors 140a, 140b operatively connected to vessel 122 to monitor the pressure, temperature, and oxygen content, respectively, within manufacturing chamber 124. As discussed in FIG. 1, mass flow controller 133 and control valve 135 may vary from the illustrated embodiment.

[0102] The oxygen sensor assembly 140, attached to a gas line 143 with a valve 141 between it and the fabrication chamber 124, is similar to the oxygen sensor assembly 40 and includes two oxygen sensors: a ppm sensor 140a and a ppb sensor 140b. However, the two systems 20, 120 may include different types of oxygen sensors. As illustrated in FIG. 1, a system may include a low-content oxygen sensor 40b and an oxygen sensor assembly that monitors oxygen content at the ppb level, and this assembly may be used in place of or in conjunction with other sensor assemblies that can derive information related to the oxygen content in the fabrication chamber 124 from the oxygen-related sensors.

[0103] Like manufacturing system 20, manufacturing system 120 includes a vacuum unit 134, such as a vacuum pump, that passes to manufacturing chamber 124 via vacuum gas line 136 fitted with control valve 137, and a vacuum port 138 formed in vessel wall 127. The vacuum unit 134, including vacuum gas line 136 and control valve 137, may be omitted if systems 20, 120 include a recirculation scrubbing system 142. Thus, an inert gas is supplied to manufacturing chamber 124, and the inert gas can be circulated through recirculation scrubbing system 142 until the impurity content within manufacturing chamber 124 is below a threshold value. For example, the inert gas can be circulated through recirculation scrubbing system 142 until the oxygen partial pressure within manufacturing chamber 124 is below about 200 ppb. Next, the metal-based feedstock present in manufacturing chamber 124 is heated by metal transformation / conversion unit 126.

[0104] A process for manufacturing / transforming / converting metals using the manufacturing system described in Figures 1-2 is provided, wherein the purity of the gaseous atmosphere within the manufacturing chamber 24, 124 of the vessel 22, 122 is monitored and / or controlled during manufacturing.

[0105] The fabrication chambers 24, 124 are first evacuated using a vacuum system 34, 134 and then refilled with a high-purity inert gas, such as argon, nitrogen, or helium, using an inert gas source 28, 128. Before entering the fabrication chambers 24, 124, the inert gas supplied by the inert gas source 28, 128 is purified in a gas purification unit 30, 130 to reduce impurity levels. Alternatively, the inert gas filling the fabrication chambers 124 may be purified using a recirculation scrubbing system 142. In this case, the vacuum system may be omitted.

[0106] The fabrication chamber 24, 124 can be evacuated to less than about 1200 Pa, less than about 100 Pa, or less than about 5 Pa. The vacuum system can have two or more vacuum pumps, with a first vacuum pump used to evacuate to less than a first threshold (e.g., about 5 Pa) and a second vacuum pump used to evacuate to another threshold (e.g., less than about 0.1 Pa) after the first threshold is reached.

[0107] For example, impurity levels may be reduced to below a threshold of about 200 ppb or about 100 ppb for at least one contaminant, or the gas purity may be less than about 50 ppb or less than about 10 ppb for at least one contaminant, depending on the embodiment. Purification of the inert gas supplied to the fabrication chamber 24, 124 should occur prior to increasing the metal temperature within the fabrication chamber 24, 124 for metal transformation / conversion. Purification of the inert gas reduces contaminant levels in the produced powder particles or consolidated bulk 3D forms.

[0108] The inert gas content of the fabrication chambers 24, 124 during operation of the metal transformation / conversion units 26, 126 is typically maintained at a contaminant level of less than about 200 ppb. In other embodiments, the gas purity is less than about 100 ppb for at least one contaminant level. The difference between the impurity content of the inert gas exiting the gas purification units 30, 130 and the impurity content of the inert gas within the fabrication chambers 24, 124 is primarily due to oxygen and other impurities diffusing into the fabrication chambers 124 of the vessel 122 during operation. As previously discussed, the impurity content of the inert gas within the fabrication chambers 24, 124 can be continuously reduced and / or maintained. Alternatively, the impurity content of the inert gas within the fabrication chambers 24, 124 may be controlled by the oxygen sensor 140 and compressor 152.

[0109] Therefore, during the metal transformation / conversion process, an inert gas is fed to a gas purification unit to reduce the oxygen partial pressure to less than about 100 ppb to obtain a purified inert gas, which is then fed into a fabrication chamber, where the metal-based feedstock can then be heated and transformed / converted into at least one final part in the metal transformation / conversion unit.

[0110] Thus, during the metal transformation / conversion process, an oxygen-related parameter can be monitored within the fabrication chamber. If the oxygen-related parameter is higher than a predetermined oxygen threshold within the fabrication chamber, an inert gas is continuously withdrawn from the fabrication chamber, and a purified gas having an oxygen partial pressure reduced to less than about 100 ppb is fed into the fabrication chamber. If the oxygen-related parameter is below the predetermined oxygen threshold within the fabrication chamber, the metal-based feedstock within the fabrication chamber can then be heated in a metal transformation / conversion device and transformed / converted into at least one final part.

[0111] Alternatively, an inert gas may be formed in a sealed container and introduced into a fabrication chamber equipped with a metal transformation / conversion unit; the inert gas may be purified before or after introduction into the fabrication chamber to reduce the oxygen partial pressure to less than about 100 ppb and obtain a purified inert gas; the purified inert gas may be present in the fabrication chamber. A metal-based feedstock may then be heated in the metal transformation / conversion unit and transformed / converted into at least one final part.

[0112] Alternatively, the gas in the fabrication chamber may be withdrawn and the fabrication chamber evacuated before the purified inert gas is introduced into the fabrication chamber. Before heating the metal-based feedstock, the gas in the fabrication chamber may be continuously withdrawn and purified, and then reintroduced into the fabrication chamber until the oxygen-related parameter in the fabrication chamber is below a predetermined threshold. The oxygen-related parameter may be oxygen partial pressure, and the threshold may be 200 ppb. Alternatively, the oxygen partial pressure of the inert gas purified in the purification unit may be less than about 100 ppb. The purified inert gas may also be heated before being introduced into the fabrication chamber, or cooled before being purified.

[0113] A gas purification unit may be located in the inert gas line between the inert gas source and the manufacturing chamber, and the inert gas from the inert gas source may be purified before being introduced into the manufacturing chamber. The purified inert gas may be heated before being introduced into the manufacturing chamber.

[0114] While the metal-based feedstock is heated in the metal transformation / conversion unit, the inert gas in the fabrication chamber may be continuously purified and then reintroduced to maintain low impurity levels during the metal transformation / conversion process. Alternatively, the purified inert gas produced in the purification unit may have an oxygen partial pressure of less than about 100 ppb. Alternatively, the purified inert gas may be heated before being reintroduced into the fabrication chamber or cooled before being purified. Oxygen-related parameters may also be monitored in the fabrication chamber, and the flow rate of the inert gas leaving the fabrication chamber may be adjusted based on the monitored oxygen-related parameters.

[0115] Alternatively, while the metal-based feedstock is heated in the metal transformation / conversion unit, the gas within the fabrication chamber may be continuously and solely vented to the surroundings, and purified inert gas may be continuously supplied into the fabrication chamber from an inert gas source.

[0116] The inert gas in the fabrication chamber may be heated while the metal-based feedstock is heated in the metal transformation / conversion unit.

[0117] As previously mentioned, the metal transformation / conversion unit 26, 126 within the sealed vessel 22, 122 granulates the metal. The high purity atmosphere within the fabrication chamber 24, 124 aids in spheroidization of the particles and reduces the likelihood of containing oxides or contaminants.

[0118] The metal transformation / conversion unit 26, 126 within the sealed vessel 22, 122 may be a sintering furnace that produces a consolidated bulk 3D form with reduced oxide formation and improved mechanical properties.

[0119] If the metal transformation / conversion unit 26, 126 in the sealed vessel 22, 122 is a 3D printer that creates solidified bulk 3D forms, a high purity atmosphere in the fabrication chamber 24, 124 can help maintain melt homogeneity and reduce oxide or contaminant content in the final 3D part.

[0120] Many metals, including aluminum, are known to form oxides with much higher melting points. This means that a drop of molten metal forms a rigid oxide film, preventing the molten metal from changing shape due to surface tension. This occurs even if the oxide layer is only a few angstroms thick, i.e., a few oxide molecular layers. Because the molten metal is highly reactive, all oxygen molecules that come into contact with the molten metal will adhere to form an oxide. Therefore, the high-purity atmosphere of the fabrication chamber 24, 124 limits the content of oxygen and other impurities within the fabrication chamber to prevent oxide formation, preventing the formation of a complete oxide layer before the droplets are sufficiently spherical.

[0121] It is known that the time to form a layer is directly related to the gas pressure. Because the fabrication chamber 24, 124 is filled with a high-purity inert gas, such as argon, nitrogen, or helium, before the fabrication process begins, the pressure of the inert gas can be ignored. Therefore, when calculating the time to form an oxide monolayer, only the oxygen partial pressure should be considered. The oxygen partial pressure in the fabrication chamber 24, 124 should be less than about 200 ppb, or less than about 100 ppb.

[0122] When the metal transformation / conversion unit 26, 126 in the sealed vessel 22 is a metal-based powder production unit for granulating aluminum into powder, the maximum threshold of oxygen partial pressure in the production chamber 24, 124 may be determined as follows: to produce spherical powder, the formation of an oxide layer on the powder particles must be prevented during powder formation and solidification. Lamb 1932 [Lamb, H. 1932, Fluid Mechanics, 6th edition, Cambridge University Press] defines the decay time for droplet spheroidization as ργ 2 / {μ(l-1)(2l+1)}. It was estimated that 5 decay times were required to eliminate all vibrations. When producing 50 μm aluminum droplets, the time required to eliminate all vibrations and obtain spherical powder particles was approximately 1100 μs. This means that the formation of an oxide monolayer on the powder particles must be avoided for more than 1100 μs. For quality control, such estimated times are multiplied by a safety factor (determined by experiment). For example, a safety factor of 10 can be selected to obtain 11 ms.

[0123] According to Sayer 1999 [SAYER, M. & MANSINGH, A. MEASUREMENT, INSTRUMENTATION AND EXPERIMENT DESIGN IN PHYSICS AND ENGINEERING, PHI Learning, 1999], it takes about 3 ns to form a monolayer at 1 atmosphere partial pressure, and a partial pressure of 200 ppb is required to extend this to 15 ms. At 100 ppb, it takes twice as long for a 68 μm droplet.

[0124] The methods / steps described above may be performed in the order stated or in any suitable order.

Claims

1. a sealed container forming a production chamber containing a total gas volume; a metal conversion unit, which includes one of an additive manufacturing unit using powder particles and a metal-based powder manufacturing unit for pulverizing a metal-based feedstock into powder particles, the powder particles having an average diameter of 10 μm to 125 μm, and is contained within the manufacturing chamber and heats the metal-based feedstock; an inert gas source operatively connected to the fabrication chamber via an inert gas line and in gaseous communication with the fabrication chamber to supply inert gas within the fabrication chamber; at least one gas purification unit in gas communication with the production chamber for purifying an inert gas to provide a purified inert gas having an oxygen partial pressure of less than 100 ppb; and a recycle scrubbing system including a closed-loop recycle gas line extending between a recycle gas inlet and a recycle gas outlet formed within said sealed vessel and in gaseous communication with said production chamber; Including, the recirculation scrubbing system recycles 1 to 50% (vol.) of the total gas volume per minute; and wherein at least one of the at least one gas purification unit is attached to and in gaseous communication with the closed loop recycle gas line to purify the inert gas flowing within the closed loop recycle gas line into the purified inert gas having an oxygen partial pressure of less than 100 ppb.

2. The metal powder-based manufacturing system of claim 1 , further comprising a vacuum unit in gas communication with the manufacturing chamber to create a vacuum within the manufacturing chamber.

3. 3. The metal powder-based manufacturing system of claim 1 or 2, wherein the metal conversion unit comprises a sintering furnace.

4. 3. The metal powder based manufacturing system of claim 1 or 2, wherein the metal conversion unit is configured to melt the metal-based feedstock and solidify the molten metal into at least one final 3D part.

5. 5. The metal powder based manufacturing system of claim 4, wherein said at least one final 3D part comprises a plurality of powder particles.

6. 3. The metal powder-based manufacturing system of claim 1 or 2, wherein the metal conversion unit is configured to heat the metal-based feedstock to a temperature below its melting point and cool the heated metal into at least one final 3D part.

7. 7. The metal powder-based manufacturing system of claim 1, wherein at least one of the at least one gas purification unit is attached to the inert gas line downstream of the inert gas source to purify the inert gas supplied by the inert gas source into a purified inert gas having an oxygen partial pressure of less than 100 ppb before being introduced into the manufacturing chamber.

8. 8. The metal powder-based manufacturing system of claim 7, further comprising a heating unit attached to the inert gas line downstream of the gas purification unit and configured to heat purified inert gas prior to introduction into the manufacturing chamber.

9. The metal powder-based manufacturing system of any one of claims 1 to 8, wherein the recirculation scrubbing system further comprises a heat exchanger.

10. 10. The metal powder-based manufacturing system of claim 1, wherein the recirculation scrubbing system further comprises a heating unit installed downstream of the at least one gas purification unit to heat the inert gas flowing inside the closed-loop recirculation gas line before introducing it into the manufacturing chamber.

11. the recirculation scrubbing system further includes a gas compressor attached to the closed-loop recirculation gas line; 11. The metal powder based manufacturing system of claim 1, further comprising: an oxygen-related sensor assembly that monitors an oxygen-related parameter within the manufacturing chamber; and a controller operatively connected to the gas compressor and the oxygen-related sensor assembly, the controller varying a speed of the gas compressor based on the oxygen-related parameter monitored by the oxygen-related sensor assembly.

12. 12. The metal powder-based manufacturing system of claim 11, wherein the oxygen-related sensor assembly comprises an oxygen sensor assembly, and the oxygen-related parameter is oxygen partial pressure.

13. 12. The metal powder-based manufacturing system of claim 11, wherein the oxygen-related sensor assembly includes a ppm oxygen sensor and a ppb oxygen sensor, the ppb oxygen sensor activating when the monitored oxygen content is below a ppm detection threshold.

14. 14. A metal powder based manufacturing system according to any one of claims 1 to 13, wherein the purified inert gas has an oxygen partial pressure of less than 50 ppb or less than 20 ppb.

15. 13. The metal powder-based manufacturing system of claim 1, further comprising a heating unit located within the manufacturing chamber and in conductive heat exchange with the manufacturing chamber to heat an inert gas contained within the manufacturing chamber.

16. 16. The metal powder-based manufacturing system of any one of claims 1 to 15, wherein the gas purification unit comprises a gas-impermeable housing containing a sorbent.

17. monitoring oxygen-related parameters within a manufacturing chamber formed within a sealed container and including a total gas volume; If the oxygen-related parameter in the fabrication chamber is greater than a predetermined oxygen threshold, continuously withdrawing 1 to 50% (vol.) of the total gas volume per minute from the fabrication chamber while the oxygen-related parameter in the fabrication chamber is greater than the predetermined oxygen threshold to obtain a withdrawn inert gas, purifying the withdrawn inert gas to reduce its oxygen partial pressure to an oxygen partial pressure of less than 100 ppb to obtain a purified inert gas, and introducing the purified inert gas into the fabrication chamber; and heating a metal-based feedstock in a metal conversion unit contained within the fabrication chamber to convert the metal-based feedstock into at least one final component if the oxygen-related parameter within the fabrication chamber is below a predetermined oxygen threshold; Including, 1. A metal conversion method, wherein the metal conversion unit comprises one of an additive manufacturing unit using powder particles and a metal-based powder production unit that pulverizes a metal-based feedstock into powder particles, the powder particles having an average diameter of 10 μm to 125 μm.

18. 18. The metal transmutation method of claim 17, wherein said oxygen-related parameter is said oxygen partial pressure and said predetermined oxygen threshold is 200 ppb.

19. 19. The metal conversion method of claim 17 or 18, further comprising the steps of: drawing gas from the fabrication chamber to create a vacuum; and supplying inert gas from an inert gas source into the fabrication chamber prior to the step of continuously drawing inert gas from the fabrication chamber.

20. 20. The metal converting method of claim 19, wherein supplying an inert gas into the fabrication chamber further comprises supplying the inert gas to a gas purification unit to reduce its oxygen partial pressure to an oxygen partial pressure of less than 100 ppb before introducing the inert gas into the fabrication chamber.

21. 21. The method for converting metals according to any one of claims 17 to 20, wherein the step of heating the metal-based feedstock comprises melting the metal-based feedstock or heating the metal-based feedstock to a temperature below its melting point.

22. 22. The metal conversion method according to any one of claims 17 to 21, further comprising the steps of: continuously withdrawing an inert gas from the production chamber while the metal-based feedstock is heated; purifying the withdrawn inert gas to reduce its oxygen partial pressure to an oxygen partial pressure of less than 100 ppb; and thereafter introducing the purified inert gas into the production chamber.

23. 23. The metal conversion method of claim 22, further comprising adjusting the flow rate of inert gas withdrawn from said fabrication chamber based on monitored oxygen-related parameters within said fabrication chamber.

24. The metal converting method according to any one of claims 17 to 23, wherein the purified inert gas introduced into the production chamber has an oxygen partial pressure of less than 50 ppb or less than 20 ppb.

25. 21. The metal conversion method of claim 20, further comprising the steps of continuously evacuating gas contained in the production chamber, supplying an inert gas to the gas purification unit, and introducing the purified inert gas into the production chamber while heating the metal-based feedstock.

26. introducing an inert gas into a manufacturing chamber having a total gas volume disposed within a sealed container containing a metal conversion unit; purifying the inert gas at least one of before and after introduction into said fabrication chamber to reduce the oxygen partial pressure to less than 100 ppb to obtain a purified inert gas; introducing a purified inert gas into the fabrication chamber; and heating a metal-based feedstock in the metal conversion unit to convert the metal-based feedstock into at least one final component within the fabrication chamber containing a purified inert gas; A method comprising: The method comprises: continuously withdrawing 1 to 50 vol% of the total gas volume per minute from the production chamber while heating the metal-based feedstock, to obtain withdrawn inert gas; purifying the withdrawn inert gas to reduce its oxygen partial pressure to less than 100 ppb; and thereafter, introducing the purified inert gas into the fabrication chamber; further comprising 1. A metal conversion method, wherein the metal conversion unit comprises one of an additive manufacturing unit using powder particles and a metal-based powder production unit that pulverizes a metal-based feedstock into powder particles, the powder particles having an average diameter of 10 μm to 125 μm.

27. 27. The metal conversion method of claim 26, further comprising the step of evacuating said fabrication chamber to a vacuum before introducing an inert gas into said fabrication chamber.

28. further comprising monitoring oxygen-related parameters within the fabrication chamber; 28. The metal transmutation method of claim 26 or 27, wherein the step of introducing purified inert gas into the fabrication chamber is performed until an oxygen-related parameter in the fabrication chamber is below a predetermined oxygen threshold.

29. 30. The metal transmutation process of claim 28, wherein said oxygen-related parameter is oxygen partial pressure and said predetermined oxygen threshold is 200 ppb.

30. 27. The metal conversion method of claim 26, wherein the step of purifying the inert gas occurs before introduction into the fabrication chamber via an inert gas line extending between an inert gas source and the fabrication chamber, having a gas purification unit attached thereto, and in gaseous communication with the gas purification unit.

31. 31. The method for converting metals according to any one of claims 26 to 30, wherein the step of heating the metal-based feedstock comprises melting the metal-based feedstock or heating the metal-based feedstock to a temperature below its melting point.

32. 32. The metal converting method of claim 26, further comprising the steps of: monitoring an oxygen-related parameter in the manufacturing chamber; and adjusting a flow rate of inert gas withdrawn from the manufacturing chamber based on the monitored oxygen-related parameter in the manufacturing chamber.

33. 31. The metal conversion process of claim 30, wherein the purified inert gas exiting the gas purification unit has an oxygen partial pressure of less than 50 ppb or less than 20 ppb.

34. 31. The metal conversion method of claim 30, further comprising the steps of continuously evacuating gas contained in the production chamber, supplying an inert gas to the gas purification unit, and introducing the purified inert gas into the production chamber while heating the metal-based feedstock.

35. A metal conversion method according to any one of claims 26 to 34, wherein the inert gas comprises at least one of argon gas, nitrogen gas, and helium gas.

36. A metal conversion method as described in any one of claims 26 to 34, further comprising the step of heating the purified inert gas prior to introducing it into the manufacturing chamber.

37. A method for metal conversion according to any one of claims 26 to 36, wherein the withdrawn inert gas is cooled before being purified.

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