Laser-assisted synthesis from ore reduction (LASOR) for additive manufacturing

Abstract

The disclosure relates to a method for additive manufacturing, the method comprising: reducing metal oxide particles, in flight, in the presence of a at least one reducing gas to form substantially reduced metal particles; melting the reduced metal particles, in flight, with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate.

Description

LASER-ASSISTED SYNTHESIS FROM ORE REDUCTION (LASOR) FOR ADDITIVE MANUFACTURINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Appl. No. 63 / 563,157, filed March 8, 2024, which is incorporated by reference as if fully set forth herein.BACKGROUND

[0002] Metal additive manufacturing (AM) has gained widespread use in sectors like aerospace, defense, and energy over the last decade. Metal AM technologies such as Direct Energy Deposition (DED) and Powder Bed Fusion (PBF) predominantly rely on specially produced metal powders. These powders, with sizes ranging from 30 to 80 pm, need to have a precise chemical composition for the final product and are produced by atomization methods like centrifugal atomization. The production of these metal alloy powders is not only costly, with a market size estimated at $11 billion and the ferrous segment comprising over 70% of the metal powder market, but it also significantly contributes to global CO2 emissions and accounts for a large proportion (—1 / 3) of the total energy consumption of AM.SUMMARY

[0003] The disclosure seeks to bypass the need for commercial iron or steel powders and the associated environmentally damaging processes described here. Further, the disclosure resolves the significant technical hurdles associated with using iron ore powders in metal production two of which are that (i) iron ore powders are over 98% iron oxides; and (ii) the tensile strength of iron oxide is markedly low — less than 2% (6 MPa) of that of commercial iron alloys (540 MPa).DESCRIPTION OF THE DRAWINGS

[0004] The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed herein.

[0005] FIG. 1 is a schematic of “Laser Assisted Synthesis from Ore Reduction” (LASOR) process.

[0006] FIGS. 2A-2C are schematics of (A) an example of a LASOR system configuration; (B) an example of a laser head: Precitec YC52 with multi-jet coaxial nozzle; and (C) an example of a powder feeder: Metco Twin 150-LC.

[0007] FIG. 3 is a plot showing the specific reduction rates of FeO by H2.

[0008] FIG. 4 is a plot illustrating the meaning of D50, D90, and D99.

[0009] FIG. 5 is a diagram of a computer simulation of H2-liquid iron oxide reduction during a Drop Tube Furnace (DTF) process.

[0010] FIG. 6 is a carton of a gas-liquid reduction for (A) liquid droplet of iron oxide during flight and (B) in molten pool. Note the gas-droplet reduction time t1 is 0(1 ms), while gas-molten pool reduction time t2 is 0(1 s).

[0011] FIG. 7 shows the theoretical estimate of the specific reduction time of iron oxide particles by H2under LASOR conditions.

[0012] Unless otherwise indicated, all figures and drawings in this document are not to scale and are chosen for the purpose of illustrating different embodiments of the invention. The dimensions of the various components are depicted in illustrative terms only, and no relationship between the dimensions of the various components should be inferred from the drawings, unless so indicated. Although terms such as “top”, “bottom”, “upper”, “lower”, “under”, “over”, “front”, “back”, “up” and “down”, and “first” and “second” can be used in this disclosure, it should be understood that those terms are used in their relative sense only unless otherwise noted.DESCRIPTION

[0013] Reference will now be made in detail to certain embodiments of the disclosed subject matter. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter.

[0014] Over the past three decades, significant research has focused on the flash reduction of oxides using Drop Tube Furnace (DTF) at a laboratory scale. Pioneering work by Hayashi et al. in the early 1990s showed that FeO particles, sized 58 pm, could achieve over 80% reduction in just 0.5 seconds using an N2-H2 gas mixture at temperatures between 1723 K and 1823 K. Qu et al. investigated the Hlsarna process (e.g., a smelting reduction process with two directly coupled process stages in which the production of liquid pig iron takes place. It is a combination of a Cyclone Converter Furnace (CCF) which is placed above the Smelting Reduction Vessel (SRV), forming a continuous, once through process) using a high-temperature DTF, achieving up to 30% partial reduction of Fe2O3 particles within 2 seconds at temperatures between 1550 K and 1750 K. Their findings indicated that smaller particle sizes (30 pm) facilitated faster reduction rates than larger particles (90 pm). They developed a computational fluid dynamics (CFD) model to simulate the reacting flow of fine Fe2Oa particles in a tube furnacefilled with H2 gas. As shown in FIG. 5, Fe20a particles with an average diameter of 100 pm fell to the bottom of the tube within half a second, and the reduction degree R (representing the percentage of iron oxide being reduced) reached 85% within 0.5 seconds at a peak temperature of 1700 K. They demonstrated that R could be further increased to 96.5% at a temperature of 1800 K. Studies by Guo et al. and Choi also underscored the critical role of temperature in enhancing reduction efficiency, given the endothermic nature of the hydrogen reduction process and its rate constant's dependence on temperature as described by the Arrhenius equation.

[0015] Additionally, the reduction of iron oxide using hydrogen plasma has been explored, with plasma arc temperatures typically exceeding 15,000 K to generate ionized hydrogen. However, the relatively low iron oxide powder temperatures (573-1073 K) required prolonged periods (0.5-2 hours) to achieve 90% reduction, indicating the potential for further optimization in these reduction processes.

[0016] Finally, there are studies exploring the use of aluminum (Al) and silicon (Si) powders as solid reduction agents to mix with iron oxide powders during laser AM. But in those processes, the problem is that the reduction degree is low. The use of Al powder as a reductant leads to a mere 2.4% iron reduction. Using Si powder as a reductant results in highly pure iron, but the size of the pure iron domain is too small (<25 pm) for industrial applications. Additionally, using Al and Si reductants leads to the formation of AI2O3 and SiO2 by-products, which must be removed to obtain functional parts.

[0017] But as far as the inventors are aware, there has been no research conducted on laser AM processes using raw iron ore as feedstock nor using hydrogen for reduction purpose.

[0018] The disclosure relates to a “Laser Assisted Synthesis from Ore Reduction” (LASOR) process for metal additive manufacturing (AM) that enables the direct transformation of raw iron ores into functional 3- dimensional (3D) components (see FIG. 1). The LASOR process involves simultaneous melting, H2 gas-liquid oxide reduction, and solidification. Hydroxide ions (OH_) are generated due to the rapid reduction induced by intense laser heating and eventually leave from the solid deposition in the form of water vapor. This approach leverages three decades of fundamental research on hydrogen gas-driven oxide reduction, marking the first known attempt to integrate in-situ reduction with metal AM.

[0019] The technological advancement proposed seeks to validate two key scientific premises:

[0020] The 1stpremise suggests that raw iron ore powders with particle sizes between 30 to 80 pm, primarily composed of Fe2C>3, can be effectively reduced to high-purity iron with a reduction degree higher than 90% during the LASOR process, aided by an assistive gas flow of H2. Hydroxide ions (OH-) are generated due to the gas-liquid reduction reaction in the laser- induced high-energy environment and eventually leave the solid deposition in the form of water vapor.

[0021] The 2ndpremise suggests that parts fabricated by LASOR show at least a 100% improvement in mechanical strength compared to those produced by laser melting of raw iron ore powders without any reduction.

[0022] This development offers significant economic, technological, and environmental benefits for cutting-edge industries and space exploration initiatives by enabling the direct use of raw iron ores in AM, thus circumventing the conventional requirements for alloy powder production, transport, and storage. The LASOR process promises to contribute to a more sustainable manufacturing landscape by reducing carbon emissions and resource consumption.

[0023] An example of an experimental apparatus that can be used for LASOR can comprise one or more of the following modules (see FIGS. 2A- 2C): laser (e.g. a 500 W continuous wave (CW) Ytterbium fiber laser (model: YLR-500-AC-Y11 , 1064 nm wavelength); laser head (e.g., a commercially available processing head (Precitec YC52, as shown in FIG. 2B) known for its application in laser cladding; the component is distinguished by its motorized laser focal position adjustment and is equipped with 4-jet powder nozzles arranged coaxially around the laser nozzle, optimizing powder delivery); powder feeder (e.g., Metco Twin 150-LC powder feeder (FIG. 2C); the model is often used for laser cladding purposes and can accurately control the powder feed rate; gas delivery (e.g., a H2cylinder to deliver the reducing gas described during LASOR, and an argon (Ar) cylinder as shielding gas for laser optics protection from contamination by any spattered droplets); a building chamber (e.g., a building chamber of 80 cm x 80 cm x100 cm.

[0024] In one example, prior to any experiment, the chamber can be vacuumed until the oxygen level is reduced to below 0.05%. Afterward, the chamber can be pressurized with, e.g., 80 psi Ar gas.

[0025] The LASOR process described and claimed herein distinguishes itself from other processes at least in the following ways. First, LASOR is specifically designed for the 3D printing process to create functional components, unlike recent hydrogen-based reduction methods that produce iron sponge. This porous sponge iron, with residual oxide content, is typically used as feedstock for steelmaking and requires further processing. Second, LASOR can utilize finer powder sizes (30~80pm) compared to the 10 mm pellets used in recent processes. And third, LASOR operates at high temperatures of approximately 2800 K and is characterized by rapid hydrogen gas-liquid reduction. This is in contrast to the solid-phase reduction process that occurs with iron pellets at temperatures ranging from 840 K to 970 K in recent processes.

[0026] The feasibility of LASOR lies at least in using the laser not only as a 3D printing tool for depositing iron ore powders into a final part but also as an energy source to facilitate the reduction reaction of iron oxide.

[0027] Over the last three decades, fundamental research has been conducted using Drop Tube Furnace (DTF) to study the flash reduction of iron oxide particles by H2 gas at the laboratory scale. The typical furnace temperature ranges from 1000 K to 1800 K, close to the melting point of iron oxide in these studies. The iron ore particle size studied ranged from 20 to 100 pm. The results reported show that the reduction degree can approach nearly 100% within 1 second of particle residence time. FIG. 3 compares the published reduction rates of iron oxide by hydrogen gas or plasma at various temperatures. The specific reaction rate r (r = kcph, where ph is the partial pressure of H2) depends on the reduction reaction rate constant kc{kc=Ae R*Ttwhere A is the pre-exponential factor, Eais the activation energy and R* is the universal gas constant). From FIG. 3, Eareduces significantly for liquid iron oxide in comparison with the solid phase reduction, and the reduction potential of hydrogen increases almost two orders of magnitude just above the melting point of iron oxide. In addition, increasing temperature can significantly improve the reaction rate.

[0028] The LASOR mechanism creates a reduction condition more favorable than flash reduction: at least because(i) The temperatures at the laser-induced droplets and the molten pool can easily reach 2800 K, i.e. , 1000 K above the melting point of iron oxide. The melting points of various iron oxides are 1644 K for FeO and 1870 K forFesCU. Based on the specific reaction rate calculation, a Fe20a particle with 50 pm diameter will be fully reduced to iron in just 0.93 milliseconds at a temperature of 2800 K, indicating that the reduction process will be finalized during the flight.(ii) The powder size ranges between 30 to 80 pm, similar to the particle size used in DTF.(iii) The molten pool size is 100-200 pm, which is small enough to complete the reduction process during deposition.(iv) The gas-liquid reduction time for the droplet in flight and in the molten pool can be engineered to 1 second or longer. LASOR has many mechanisms for process control and can be optimized by adjusting the laser power, scanning speed, hydrogen gas flow rate, and powder size, to create an even higher temperature, longer reaction time, and a reduction condition more favorable than flash reduction.

[0029] Consequently, LASOR’s combination of the laser with a H2 atmosphere will effectively reduce iron ore at this finer scale, ensuring hot gas-liquid interaction. The by-products, primarily water vapor, can be easily removed from the chamber, leaving enriched iron in the printed parts.

[0030] In addition to the LASOR apparatus design, the disclosure relates to a method for additive manufacturing, the method comprising: reducing metal oxide particles, in flight, in the presence of at least one reducing gas to form reduced metal particles; melting the reduced metal particles, in flight, with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate.

[0031] As used herein, the term “in flight” generally refers to metal particles that are suspended or carried in the at least one reducing gas and / or assist gas and are being moved along the path of the at least one reducing gas and / or assist gas.

[0032] The disclosure also relates to a method for additive manufacturing, the method comprising: depositing metal oxide particles on a substrate; reducing the metal oxide particles in the presence of at least one reducing gas to form reduced metal particles; and melting the reduced metal particles with a laser beam to form molten metal droplets. After the molten metal droplets solidify sufficiently, additional metal oxide particles can be deposited on the substrate. Then, the methodcomprises reducing the metal oxide particles in the presence of at least one reducing gas to form reduced metal particles; and melting the reduced metal particles with a laser beam to form molten metal droplets. This process can be repeated as many times as necessary to complete the additive manufacturing of a metal part. This process can be applied to both Directed Energy Deposition (DED) and Powder Bed Fusion (PBF) configurations. In DED, also referred to as Laser Metal Deposition (LMD), metal oxide powders are continuously fed through a nozzle, reduced in-flight using a reducing gas, melted by a laser beam, and deposited onto the substrate layer by layer. In PBF, including Selective Laser Melting (SLM), a thin layer of metal oxide powder is spread over a substrate, selectively fused by a laser or electron beam, and reduced in a controlled atmosphere. Unlike DED, there is no flight motion in PBF, as the powders remain stationary and are processed layer by layer.

[0033] The metal oxide particles used in the methods described herein can be substantially only metal oxide particles or can be a mixture of metal oxide particles and reduced metal particles. In one example, the metal oxide particles can be comprised in a 1 :1 mixture of metal oxide particles and reduced metal particles, such as a 1 :1 mixture of Fe(0) and FexOy, wherein x is 2 or 3 and y is 3.

[0034] As used herein, the term “reduced metal particles” generally refers to metal particles that are substantially reduced or to a mixture or distribution of partially reduced and unreduced metal oxide particles. Thus, for example, the term “reduced metal particles” can refer to a mixture of reduced metal particles and metal oxide particles in a ratio ranging from 1 :10 to 10:1 , where 1 :10 represents a lower degree of reduction and 10:1 represents a highly reduced material with minimal residual oxides. In some cases, the ratio may extend beyond this range depending on processing conditions, but the practical upper limit is generally governed by near-complete reduction of metal oxides.

[0035] The metal oxide particles and the reduced metal particles are suspended in the reducing gas and flow axially toward the substrate. See, e.g., FIG. 1. The axial flow of the metal oxide particles and / or the reduced metal particles can substantially perpendicular to a surface of the substrate. In one example, the suspension of the metal oxide particles and / or reduced metal particles comprises a suitable concentration of metal oxide particles and / or reduced metal particles.

[0036] Any suitable reducing gas can be used in the methods described herein. Examples of reducing gases include, but are not limited to, gases comprising hydrogen (H2), methane (CH4), or carbon monoxide (CO) or combinations thereof.

[0037] Hydrogen is considered a new alternative reductant for ironmaking to replace fossil fuels due to its high reduction efficiency and the production of water vapor as the only by-product. An example of recent industrial adoption is the H2 Green Steel company in Sweden. For these direct reduction processes with hydrogen, iron ore pellets with a typical pellet size of 10 mm are processed in a blast furnace with temperatures ranging from 840 K to 1470 K. Given the relatively low temperature and large pellet size, the reduction progresses through several stages — from hematite (Fe2Oa) to magnetite (FeaO^, from magnetite to wustite (FeO), and finally from wustite to sponge iron (highly porous Fe) — resulting in a reduction process lasting about 2 hours.

[0038] The metal oxide particles that can be used in the methods described herein can comprise oxides of iron, cobalt, chromium, copper, and copper or combinations thereof. For example, the metal oxide particles can comprise FexOy, CozOp CrpOd, CupOd or combinations thereof, wherein x is 2 or 3, y is 3 or 4, z is 1 , 2, or 3; p is 1 , 3, or 4; and d is 1 , 2, or 3.

[0039] The metal oxide particles can have any suitable size and any suitable particle size distribution. At least three values are typically used to characterize particle size distribution: D50, D90, and D99. These values are points along the distribution curve as pictured in FIG. 4. For example, D50 is defined as the particle size below which 50% of the particles fall, representing the median size of the distribution. D90 and D99 are similarly defined as the points along the distribution curve where 90% and 99% of the particles, respectively, are smaller than the indicated value. In one example, the metal oxide particles have a D99 of about 30 pm to about 80 pm, a D90 of about 20 pm to about 100 pm, and a D50 of about 30 pm to about 100 pm.

[0040] Any suitable laser can be used in the methods described herein. For example, the laser beam used in the methods can be a laser beam produced by a continuous wave laser. In one example, the laser has a power output of at least about 100 W, at least about 200 W, at least about 300 W, at least about 500 W or at least about 1 kW, such as from about 100 W to about 3 kW, about 500 W to about 2 kW or about 200 W to about 1 kW.

[0041] The metal droplets produced by the methods described herein can be deposited on the substrate to form a metal alloy. Examples of suitable metal alloys include cobalt-iron (Co-Fe) alloys, iron-nickel (Fe-Ni) alloys, and nickeliron (NiFe) alloys. Additionally, the alloys may comprise aluminum-based (e.g., Al-Cu, Al-Mg), copper-based (e.g., Cu-Ni, Cu-Sn), chromium-based (e.g., Fe-Cr, Ni-Cr, Co-Cr), molybdenum-based (e.g., Mo-Ni, Mo-Cr), or tungsten-based (e.g., W-Ni-Fe, W-Co) compositions. The substrate can be a steel plate or another suitable material.

[0042] The methods of the disclosure can further comprise the additive manufacturing of a metal part by depositing a plurality of metal droplets to form a plurality of metal layers on the substrate.

[0043] The disclosure includes a method for additive manufacturing, the method comprising: providing a plurality of metal oxide particles suspended in an assist gas comprising a reducing gas to form a plurality of substantially reduced metal particles suspended in the assist gas; melting the reduced metal particles suspended in the assist gas with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate.

[0044] As used herein, the term “assist gas” generally refers to a gas or gas mixture that facilitates the reduction and transport of metal oxide particles during the LASOR process. In Directed Energy Deposition (DED), the assist gas is used to blow the metal oxide particles through the nozzle, creating a controlled powder stream for deposition. In Selective Laser Melting (SLM), the assist gas surrounds the metal particles and substrate within the build chamber, helping to maintain a controlled atmosphere for reduction and fusion. The assist gas can be pure hydrogen (H2), a mixture of hydrogen and argon (H2 / Ar), or a mixture of hydrogen and nitrogen (H2 / N2). The composition of the assist gas can be adjusted based on process requirements, such as optimizing reduction efficiency, controlling reaction kinetics, stabilizing the powder flow in DED, and preventing oxidation during deposition in both DED and SLM.

[0045] The disclosure also includes a metal part made by any of the methods described herein. The LASOR process is particularly suited for space manufacturing and in-situ resource utilization (ISRU), where raw metal oxides, such as iron ore, can be directly converted into functional components without extensive material processing. Additionally, this method can be applied to the production of low-cost metal parts for construction, infrastructure, and industrialapplications, where high precision is not required. By eliminating the need for pre- processed metal powders, LASOR offers a more sustainable and economical approach to manufacturing in remote or resource-limited environments.

[0046] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range were explicitly recited. For example, a range of “about 0.1% to about 5%” or “about 0.1 % to 5%” should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1 %, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1 % to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “about X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

[0047] In this document, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting. Further, information that is relevant to a section heading can occur within or outside of that particular section. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

[0048] In the methods described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed step of doing X and a claimed step of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

[0049] The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1 % of a stated value or of a stated limit of a range.

[0050] The term “substantially” as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

[0051] The term “substantially no” as used herein refers to less than about 30%, 25%, 20%, 15%, 10%, 5%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, 0.001 %, or at less than about 0.0005% or less or about 0% or 0%.

[0052] Those skilled in the art will appreciate that many modifications to the embodiments described herein are possible without departing from the spirit and scope of the present disclosure. Thus, the description is not intended and should not be construed to be limited to the examples given but should be granted the full breadth of protection afforded by the appended claims and equivalents thereto. In addition, it is possible to use some of the features of the present disclosure without the corresponding use of other features. Accordingly, the foregoing description of or illustrative embodiments is provided for the purpose of illustrating the principles of the present disclosure and not in limitation thereof and can include modification thereto and permutations thereof.

[0053] The following Embodiments are part of the disclosure and are listed in on particular order of importance.

[0054] Embodiment 1 relates to a method for additive manufacturing, the method comprising: reducing metal oxide particles, in flight, in the presence of at least one reducing gas to form substantially reduced metal particles; melting the reduced metal particles, in flight, with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate.

[0055] Embodiment 2 relates to the method of Embodiment 1 , wherein the metal oxide particles and the reduced metal particles are suspended in the reducing gas and flow axially toward the substrate.

[0056] Embodiment 3 relates to the method of Embodiment 2, wherein the axial flow of the metal oxide particles and / or the reduced metal particles is substantially perpendicular to a surface of the substrate.

[0057] Embodiment 4 relates to the method of Embodiment 1 , wherein the reducing gas comprises hydrogen (H2), methane (CH4), or carbon monoxide (CO) or combinations thereof.

[0058] Embodiment 5 relates to the method of Embodiment 1 , wherein the metal oxide particles comprise oxides of iron, cobalt, chromium, copper, and copper or combinations thereof.

[0059] Embodiment 6 relates to the method of Embodiment 1 , wherein the metal oxide particles comprise FexOy, CozOpCrpOd, CupOd or combinations thereof, wherein x is 2 or 3, y is 3 or 4, z is 1 , 2, or 3; p is 1 , 3, or 4; and d is 1 , 2, or 3.

[0060] Embodiment 7 relates to the method of Embodiment 1 , wherein the laser beam is produced by a continuous wave laser.

[0061] Embodiment 8 relates to the method of Embodiment 7, wherein the laser has a power output of at least 200 W.

[0062] Embodiment 9 relates to the method of Embodiment 1 , wherein the metal oxide particles have a D99 of about 30 pm to about 80 pm.

[0063] Embodiment 10 relates to the method of Embodiment 1 , wherein the metal oxide particles have a D90 of about 20 pm to about 100 pm.

[0064] Embodiment 11 relates to the method of Embodiment 1 , wherein the metal oxide particles have a D50 of about 20 pm to about 120 pm.

[0065] Embodiment 12 relates to the method of Embodiment 1 , wherein the metal droplets deposited on the substrate comprise a metal alloy.

[0066] Embodiment 13 relates to the method of Embodiment 1 , wherein the metal alloy is a cobalt-iron (Co-Fe) alloy, an iron-nickel alloy, or a nickel-iron alloy (NiFe).

[0067] Embodiment 14 relates to the method of Embodiment 1 , further comprising the additive manufacturing of a metal part by depositing a plurality of metal droplets to form a plurality of metal layers on the substrate.

[0068] Embodiment 15 relates to a method for additive manufacturing, the method comprising: providing a plurality of metal oxide particles suspended in an assist gas comprising a reducing gas to form a plurality of substantially reduced metal particles suspended in the assist gas; melting the reduced metal particles suspended in the assist gas with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate.

[0069] Embodiment 16 relates to a metal part made by the method of Embodiment 1 or Embodiment 15.

[0070] Embodiment 17 relates to a method for additive manufacturing, the method comprising: reducing metal oxide particles, in flight, in the presence of at least one reducing gas before or during melting to form substantially reduced metal particles; melting the reduced metal particles, in flight, with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate using a directed energy deposition (DED) or powder bed fusion (PBF) configuration.

[0071] Embodiment 18 relates to the method of Embodiment 17, wherein the metal oxide particles and the reduced metal particles are suspended in the reducing gas and flow axially toward the substrate, wherein the assist gas facilitates particle transport through a nozzle for DED or maintains a controlled atmosphere in PBF.

[0072] Embodiment 19 relates to the method of Embodiment 18, wherein the axial flow of the metal oxide particles and / or the reduced metal particles is substantially perpendicular to a surface of the substrate.

[0073] Embodiment 20 relates to the method of Embodiment 17, wherein the reducing gas comprises hydrogen (H2), methane (CH4), or carbon monoxide (CO), or combinations thereof, wherein the reducing gas facilitates in-flight reduction and / or stabilizes the molten droplets during deposition.

[0074] Embodiment 21 relates to the method of Embodiment 17, wherein the metal oxide particles comprise oxides of iron, cobalt, chromium, copper, and other transition metals or combinations thereof.

[0075] Embodiment 22 relates to the method of Embodiment 17, wherein the metal oxide particles comprise FexOy, CozOp, CrpOd, CupOd, or combinations thereof, wherein x is 2 or 3, y is 3 or 4, z is 1 , 2, or 3; p is 1 , 3, or 4; and d is 1 , 2, or 3.

[0076] Embodiment 23 relates to the method of Embodiment 17, wherein the laser beam is produced by a continuous wave laser.

[0077] Embodiment 24 relates to the method of Embodiment 23, wherein the laser has a power output of at least 200 W.

[0078] Embodiment 25 relates to the method of Embodiment 17, wherein the metal oxide particles have a D99 of about 30 pm to about 80 pm.

[0079] Embodiment 26 relates to the method of Embodiment 17, wherein the metal oxide particles have a D90 of about 20 pm to about 100 pm.

[0080] Embodiment 27 relates to the method of Embodiment 17, wherein the metal oxide particles have a D50 of about 30 pm to about 100 pm.

[0081] Embodiment 28 relates to the method of Embodiment 17, wherein the metal droplets deposited on the substrate comprise a metal alloy, including but not limited to iron-based alloys, cobalt-based alloys, nickel-based alloys, or other transition metal alloys.

[0082] Embodiment 29 relates to the method of Embodiment 17, wherein the metal alloy is selected from the group consisting of cobalt-iron (Co-Fe) alloys, iron-nickel (Fe-Ni) alloys, nickel-iron (NiFe) alloys, low-carbon steel, cast iron, and other iron-based structural alloys.

[0083] Embodiment 30 relates to the method of Embodiment 17, further comprising the additive manufacturing of a metal part by depositing a plurality of metal droplets to form a plurality of metal layers on the substrate.

[0084] Embodiment 31 relates to a method for additive manufacturing, the method comprising: providing a plurality of metal oxide particles suspended in an assist gas comprising a reducing gas to transport the metal oxide particles toward the substrate; reducing the metal oxide particles in-flight or in a controlled chamber atmosphere to form substantially reduced metal particles; melting the reduced metal particles suspended in the assist gas with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate using a directed energy deposition (DED) or powder bed fusion (PBF) process.

[0085] Embodiment 32 relates to a metal part made by the method of Embodiment 17 or Embodiment 31.

[0086] Embodiment 33 relates to the method of Embodiment 17, wherein the additive manufacturing process is used for in-situ resource utilization (ISRII) to manufacture metal components directly from raw ore sources in extraterrestrial environments or remote locations.

[0087] Embodiment 34 relates to the method of Embodiment 17, wherein the additive manufacturing process is applied to the production of low-cost structural metal parts for construction, infrastructure, or industrial applications.EXAMPLESExample 1

[0088] One question to address is the degree to which the reduction reaction progresses under high-temperature laser heating in a powder stream. As illustrated in FIG. 6, H2gas-liquid reduction begins when the laser induces droplet formation mid-flight (A) and continues within the molten pool as the droplet descends onto the substrate (B). The droplet in-flight time, t1 , is estimated to be on the order of millisecond (ms), based on typical laser DED processes. The reduction time within the molten pool, t2, occurs on the order of seconds, which can be extended by adjusting the laser scanning speed (e.g., to 0.1 mm / s). As such, the total gas-liquid reduction time for the droplet in-flight and in the molten pool can be engineered to last up to several seconds or more.

[0089] LASOR offers multiple mechanisms for process control, enabling a more favorable reduction condition than DTF by adjusting laser power, scanning speed, hydrogen gas flow rate, and powder size for complete reduction during deposition. a. The temperatures at the laser-melted droplets and the molten pool can easily reach 2800 K, i.e., 1000 K above the melting point of iron oxide. The melting points of various iron oxides are 1644 K for FeO and 1870 K for FesO4. b. The powder size ranges between 30 to 80 pm, similar to the particle size used in DTF. c. The molten pool size is 100-200 pm, which is small enough to complete the reduction process during deposition. d. Fig. 7 shows the theoretical estimate that a Fe2Oa particle with 50 pm diameter will be fully reduced to iron in just 0.93 ms at a temperature of 2800 K. For powders ranging from 30 to 80 pm, the complete reduction time is estimated to be around 1 ms or less in LASOR.

[0090] Consequently, LASOR's combination of the laser with a H2atmosphere is anticipated to effectively reduce iron ore at this finer scale, ensuring hot gas-liquid interaction. The by-products, primarily water vapor, can be easily removed from the chamber, leaving enriched metals in the printed parts.

[0091] To the best of the inventors’ knowledge, no prior research has explored the use of raw metal ores as feedstock in laser additive manufacturing (AM), nor has hydrogen been used as a reductant in suchprocesses. Some studies have attempted to use aluminum (Al) and silicon (Si) powders as reductants mixed with iron oxide during laser AM. However, these methods have shown limited success. For example, using Al powder achieves only a 2.4% reduction in iron, while Si powder produces highly pure iron, but the domains are too small (<25 pm) for industrial applications. Additionally, using Al and Si reductants leads to the formation of AI2O3 and SiC>2 by-products, which complicate the process by requiring further removal steps to achieve functional parts.

[0092] Hydrogen, by contrast, offers a more efficient and environmentally friendly reductant, producing water vapor as the only by-product. An example of recent industrial adoption is the H2 Green Steel company in Sweden. In these large-scale direct reduction methods, iron ore pellets (~10 mm) are processed at temperatures between 840 K and 970 K, moving through multiple stages — from hematite (Fe2O3) to magnetite (Fe3O4), wustite (FeO), and finally to sponge iron (highly porous Fe). This process typically takes around two hours. However, the long reaction times and large pellet sizes pose challenges when applying these methods to high-precision, faster- paced processes like AM.

[0093] In laboratory-scale research, flash reduction using drop tube furnaces has been extensively studied over the past four decades. Hayashi et al. demonstrated that FeO particles with a diameter of 58 pm could achieve over 80% reduction within 0.5 seconds at temperatures between 1723 K and 1823 K using an N2-H2gas mixture. Qu et al. further explored the reduction of Fe2O3particles (30 pm) using high temperature DTF and achieved up to 30% partial reduction in 2 seconds at temperatures between 1550 K and 1750 K. As shown in FIG. 5, computational simulations of Fe2O3particles (100 pm) falling in a hydrogen-filled tube furnace suggest that 85% reduction can be achieved within 0.5 seconds at 1700 K, with potential for 96.5% reduction at 1800 K. Studies by Guo et al. and Choi also highlighted the critical role of smaller particle sizes and higher temperatures in accelerating reduction. Recent studies have also explored hydrogen plasma reduction, where plasma temperatures exceed 15,000 K. However, the relatively low iron oxide powder temperatures (573-1073 K) required prolonged periods (0.5-2 hours) to achieve 90% reduction, indicating the potential for further optimization in these reduction processes.

[0094] The inventors hypothesize that fine metal ore powders, such as iron ore (Fe2O3) with particle sizes ranging from 30 to 80 pm, can be effectivelyreduced with a reduction degree exceeding 90% during the LASOR process, aided by an assistive H2gas flow. Hydroxide ions (OH“) will form due to the gas-liquid reduction reaction under the laser-induced high-energy environment and will be expelled from the solid deposition as water vapor. The resulting solidification of multiple alloys will form a functional alloy with significantly improved mechanical properties.

Claims

What is claimed is:

1. A method for additive manufacturing, the method comprising: reducing metal oxide particles, in flight, in the presence of at least one reducing gas before or during melting to form substantially reduced metal particles; melting the reduced metal particles, in flight, with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate using a directed energy deposition (DED) or powder bed fusion (PBF) configuration.

2. The method of claim 1 , wherein the metal oxide particles and the reduced metal particles are suspended in the reducing gas and flow axially toward the substrate, wherein the assist gas facilitates particle transport through a nozzle for DED or maintains a controlled atmosphere in PBF.

3. The method of claim 2, wherein the axial flow of the metal oxide particles and / or the reduced metal particles is substantially perpendicular to a surface of the substrate.

4. The method of claim 1 , wherein the reducing gas comprises hydrogen (H2), methane (CH4), or carbon monoxide (CO), or combinations thereof, wherein the reducing gas facilitates in-flight reduction and / or stabilizes the molten droplets during deposition.

5. The method of claim 1 , wherein the metal oxide particles comprise oxides of iron, cobalt, chromium, copper, and other transition metals or combinations thereof.

6. The method of claim 1 , wherein the metal oxide particles comprise FexOy, CozOp, CrpOd, CupOd, or combinations thereof, wherein x is 2 or 3, y is 3 or 4, z is 1 , 2, or 3; p is 1 , 3, or 4; and d is 1 , 2, or 3.

7. The method of claim 1 , wherein the laser beam is produced by a continuous wave laser.

8. The method of claim 7, wherein the laser has a power output of at least200 W.

9. The method of claim 1 , wherein the metal oxide particles have a D99 of about 30 pm to about 80 pm.

10. The method of claim 1 , wherein the metal oxide particles have a D90 of about 20 pm to about 100 pm.

11. The method of claim 1 , wherein the metal oxide particles have a D50 of about 30 pm to about 100 pm.

12. The method of claim 1 , wherein the metal droplets deposited on the substrate comprise a metal alloy, including but not limited to iron-based alloys, cobalt-based alloys, nickel-based alloys, or other transition metal alloys.

13. The method of claim 1 , wherein the metal alloy is selected from the group consisting of cobalt-iron (Co-Fe) alloys, iron-nickel (Fe-Ni) alloys, nickel-iron (NiFe) alloys, low-carbon steel, cast iron, and other iron-based structural alloys.

14. The method of claim 1 , further comprising the additive manufacturing of a metal part by depositing a plurality of metal droplets to form a plurality of metal layers on the substrate.

15. A method for additive manufacturing, the method comprising: providing a plurality of metal oxide particles suspended in an assist gas comprising a reducing gas to transport the metal oxide particles toward the substrate; reducing the metal oxide particles in-flight or in a controlled chamber atmosphere to form substantially reduced metal particles; melting the reduced metal particles suspended in the assist gas with a laser beam to form molten metal droplets; and depositing the metal droplets on a substrate using a directed energy deposition (DED) or powder bed fusion (PBF) process.

16. A metal part made by the method of claim 1 or claim 15.

17. The method of claim 1 , wherein the additive manufacturing process is used for in-situ resource utilization (ISRII) to manufacture metal components directly from raw ore sources in extraterrestrial environments or remote locations.

18. The method of claim 1, wherein the additive manufacturing process is applied to the production of low-cost structural metal parts for construction, infrastructure, or industrial applications.

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