Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/16—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed
  • B05B7/22—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B4/00—Electrothermal treatment of ores or metallurgical products for obtaining metals or alloys
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/06—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/50—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges
  • C23C16/513—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges using plasma jets
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/134—Plasma spraying
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
  • H01J37/32055—Arc discharge
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/26—Plasma torches
  • H05H1/32—Plasma torches using an arc
  • H05H1/42—Plasma torches using an arc with provisions for introducing materials into the plasma, e.g. powder or liquid

Definitions

• the invention relates to the production and additive manufacturing of metals and alloys using plasma sources.
• Iodide vapor may be formed by heating the metal iodide (Til 4 and Zril 4 , for example, are volatile solids at room temperature) or exposing the metal, heated to an intermediate temperature, to iodine vapor.
• the Van Arkel process can, in principle, be used with any metal iodide amenable to thermal decomposition in its vapor phase.
• any metal iodide amenable to thermal decomposition in its vapor phase ea rly investigators deemed the production of Be from solid Bel 2 unfeasible, in view of unfavorable reaction kinetics at the melting point of Be. See R.S. Babu & C.K. Gupta, Beryllium Extraction— A Review, 4 Min. Proc. & Extract. Met. 39, 74 (1988).
• the conventional Van Arkel process is inherently slow, and therefore uneconomical for all but niche applications which require relatively small amounts of extremely pure metal.
• Ti and Zr metal is now produced using the more economically viable Kroll process, in which metal tetrachloride is reduced with batches of molten Mg to form metal sponge intermixed with MgCI 2 and unreacted Mg. Alloys of Ti and Zr are nevertheless still expensive. For example, even though liquid TiCI 4 costs only a few Euros per kg, the combined costs of producing Ti sponge and processing leave a standard Ti-6AI-4V alloy ingot costing a few tens of Euros per kg.
• additive manufacturing technologies employ a localized heat source— typically an electron beam, laser or plasma arc— to heat and melt feedstock— typically in the form of wire or powder— as it is applied in successive layers to well-defined regions of a work-piece to create a finished, or nearly finished, three-dimensional shaped component.
• a localized heat source typically an electron beam, laser or plasma arc
• melt feedstock typically in the form of wire or powder
• US Pat. App. No. 2006/0185473 proposes additive manufacturing of shaped titanium components using a maneuverable plasma transferred arc (“PTA”) welding torch directed towards a work-piece, coupled with means for feeding Ti sponge/ceramic particles into the torch and Ti/Ti alloy wire into the melt pool formed at the surface of the work-piece by the torch output.
• PTA maneuverable plasma transferred arc
• Til 4 has been used successfully, in combination with H 2 and other gases, in plasma chemical vapor deposition ("PCVD") to form the extremely thin Ti and Ti 3 N 4 films used in microelectronics. See, e.g., US Pat. No. 7,033,939 (Micron Techs., Inc.).
• the present invention overcomes the above and other limitations of the prior art by enabling production of metals and alloys in bulk and powder form, and additive manufacturing of metal alloy components, using metal iodides in a directed plasma system.
• a method for forming a material comprising a first metal comprising the steps of furnishing a plasma head comprising a plasma generation volume, establishing a first flow comprising an inert gas traversing the plasma generation volume and plasma head, applying a plasma voltage across the plasma generation volume to establish a plasma arc comprising an internal portion confined within the plasma head, establishing a second flow comprising a first metal iodide configured to combine with the first flow and traverse at least a portion of the plasma arc, regulating the first and second flows and plasma power to fully decompose at least a substantial fraction of the first metal iodide in the combined flow, directing at least a fraction of the combined flow comprising the at least a substantial fraction of fully decomposed first metal iodide to contact a region of a surface of the work-piece, and depositing a material comprising the first metal on at least a fraction of the region.
• the method further comprises forming an external portion of the plasma arc extending outside the plasma head, optionally contacting at least a fraction of the region with the external portion of the plasma arc and optionally establishing a transfer voltage between the work-piece and plasma head to form a transferred plasma arc.
• the method further comprises combining the second flow comprising the first metal iodide with the first flow before the first flow exits the plasma generation volume, before the first flow exits the plasma head, or in the external portion of the plasma arc.
• the method further comprises establishing a third flow comprising a second metal iodide configured to combine with the first flow and traverse at least a portion of the plasma arc, regulating the first, second and third flows and plasma power to fully decompose at least a substantial fraction of the first and second metal iodides in the combined flow, directing at least a fraction of the combined flow comprising the at least a substantial fraction of fully decomposed first and second metal iodides to contact a region of a surface of the work-piece, and depositing a material comprising an alloy of the first and second metals on at least a fraction of the region.
• the method further comprises combining the third flow comprising the second metal iodide with the first flow before the first flow exits the plasma generation volume, before the first flow exits the plasma head, or in the external portion of the plasma arc.
• the method further comprises establishing a fourth flow comprising a third metal iodide configured to combine with the first flow and traverse at least a portion of the plasma arc, regulating the first, second, third and fourth flows and plasma power to fully decompose at least a substantial fraction of the first, second and third metal iodides in the combined flow, directing at least a fraction of the combined flow comprising the at least a substantial fraction of fully decomposed fi rst, second and third metal iodides to contact a region of a surface of the work-piece. And depositing a material comprising an alloy of the first, second and third metals on at least a fraction of the region.
• the method further comprises combining the fourth flow comprising the third metal iodide with the first flow before the first flow exits the plasma generation volume, before the first flow exits the plasma head, or in the external portion of the plasma arc.
• the method further comprises at least one of the metal iodide flows comprising at least a substantial fraction of metal iodide in a solid, liquid or gas phase when it combines with the first flow.
• the first metal iodide is selected from the group consisting of Til 4 , Zrl 4 or Bel 2
• the second and third metal iodides from the group consisting of Vl 3 , All 3 , Zrl 4 , Bel 2 , Hfl 4 , Nbl 3 , Tal 3 , Bl 3 , Sil 4 , Sml 2 , Gdl 3 , Ndl 3 , Thl 4 , Mol 2 , Col 2 , Nil 2 , Mgl 2 , Snl 4 and Cl 4 .
• the method further comprises delivering microwave energy into the at least a portion of the combined flow at a frequency spectrum and power selected to break apart at least one metal-iodine species
• the method further comprises introducing a seeding material into the combined flow to condense clusters comprising the one or more metals in the at least a fraction of the combined flow comprising at least a substantial fraction of the one or more fully decomposed metal iodides.
• the seeding material may traverse at least a portion of the internal or external or no portion of the plasma arc, and may comprise metal particles, selected, for example, from the group consisting of Al, V, Si, B, Mo, Be and Ti, or ceramic particles, selected, for example, from the group consisting of TiB 2 , SiC, WC, BN, Y 2 0 3 and Zr0 2 .
• the at least a portion of the fraction of the combined flow contacting the region further may comprise hydrogen or one or more of the first, second, third or fourth flows may further comprise hydrogen.
• the deposited material is deposited in a molten state and in others in a solid state. In other embodiments, an additional heat source is applied to the deposited material.
• a controlled relative motion of plasma head and work-piece is applied to form successive layers of deposited material in different regions of the work-piece to create a shaped component.
• the flow from the outlet to the work-piece is surrounded with an inert gas shield, and the work-piece and plasma head are furnished in a vacuum chamber.
• a system is provided for implementing any of the above methods, wherein the plasma generation volume is defined by an outer surface of an elongated cathode and an inner surface of a coaxially disposed anode, and wherein the first flow comprising an inert gas passes through a first opening formed in a lower surface of the plasma head.
• the plasma head further comprises a substantially coaxial shield and a substantially annular opening disposed coaxially in the lower surface of the plasma head with respect to the first opening, and wherein an axially symmetric volume is defined by an outer surface of the anode and an inner surface of the shield and configured to deliver a gas flow from an upper portion of the plasma head through the annular opening.
• the flow from the annular opening is configured to be substantially parallel with and enclose the flow from the first opening, intersect the flow from the first opening or intersect the external portion of the plasma arc.
• the plasma head comprises a feeder for directing a flow of at least one metal iodide into the coaxial volume, into the plasma generation volume, or into the flow between the plasma head and work-piece.
• the system further comprises one or more of an induction source disposed to deliver microwave energy to the combined flow from the plasma head, a means for delivering at least one additional material directly to the deposited material on the region, a heat source configured to deliver heat directly to the deposited material on the region, control mechanisms for translating the work-piece and the plasma head, a vacuum-pumped chamber housing the work-piece and plasma head and a means for condensing iodine disposed in the vacuum chamber.
• Figure 1 is a schematic of part of a plasma system illustrating features of the invention.
• Figure 2 is a schematic of part of a plasma system illustrating features of the invention.
• Various features of the invention are described herein with reference to the figures, the written description and claims. These features may be combined with or interchanged in any permutation other than one in which the features are mutually exclusive.
• Comprising is used to mean including but not limited to.
• Confined is used to mean within but not necessarily filling a defined volume or space. Combined is used to mean substantially but not necessarily completed united or joined.
• Work-piece and work-piece surface are used to refer to the object and surface onto which deposition is performed, which may include a substrate, not necessarily comprising the metal or alloy being deposited, and may include already deposited metal or alloy material, including a portion of a metal or alloy component.
• Different plasma sources may be configured to establish a plasma arc in a flow comprising an inert gas that may be combined with a flow of one or metal iodides to form a directed combined flow comprising one or more metals formed by decomposition of the metal iodide or iodides, suitable for depositing a material comprising a metal or alloy on a work-piece.
• Plasma head 10 of a type commonly referred to as a plasma torch when operated to produce an external plasma arc.
• Plasma head 10 comprises an axially disposed cathode 1 partially enclosed by a more-or-less axially symmetrical hollow anode 2, with the space between the outer surface of cathode 1 and the inner surface of anode 2 defining a plasma generation volume 11 adapted to accommodate a first flow, shown schematically in Figure 1 by the arrows contained within coaxial volume 11, comprising an inert gas, typically argon, that enters the upper portion of the head through an inlet (not shown) and exits the plasma generation volume, and optionally the plasma head 10, through opening 9, which is typically axially symmetric and disposed in the base of anode 2 aligned with axis of cathode 1. (Required electrical connections and the upper portions of cathode 1, anode 2 and plasma generation volume 11 are not shown.)
• a plasma arc may be generated within plasma generation volume 11 by applying an appropriate high voltage (of the order of 10 kV) between cathode 1 and anode 2 across the first flow comprising an inert gas.
• an appropriate high voltage of the order of 10 kV
• the first flow namely by regulating the composition, mass flow and/or inlet pressure
• the plasma power typically between 1 and 10 kW, namely by regulating the plasma voltage and current
• a range of plasma arc configurations may be established for a given plasma head geometry.
• An internal portion of the plasma arc, with a defined temperature and pressure distribution and spatial extent confined within the plasma head, may be established in at least part of the plasma generation volume 11, and an optional external portion of the plasma arc, with a defined temperature and pressure distribution and spatial extent extending at least some way through opening 9, may be established outside the head.
• plasma arc temperature and pressure may be substantially increased.
• pressure may vary between around 0.1 to around 100 kPa and temperature, between around 3000 to around 5000 K, with the diameter of the opening 9 in the base of the plasma head 10 typically varying from around a few 100 microns to around a few cm. (Though not shown in the figures, anode 2 may be cooled by internal water flow.)
• the pressure and temperature distribution and spatial extent of the external portion of the plasma arc may be further influenced by factors such as external gas flows, the relative location of the work-piece, and the presence of a transfer voltage between work-piece and plasma head that induces the external plasma arc to contact the work- piece surface 8, forming a so-called plasma-transferred-arc ("PTA").
• PTA plasma-transferred-arc
• a PTA may be more directed than a non-PTA and a more efficient means to transfer heat energy to material deposited on the work-piece.
• plasma head 10 may further comprise a more-or-less axially symmetrical element 3 partially enclosing anode 2, with the space between anode 2 and element 3 defining a coaxial volume 12 adapted to accommodate a flow, shown schematically by the dashed arrows contained within coaxial volume 12 in Figure 1, between the upper portion of the head and a more-or-less annular opening 13 defined by the lower end of element 3 and the outer surface of anode 2.
• the flow typically comprising an inert gas, traversing coaxial volume 12 may also serve to cool anode 2.
• the lower end of element 3 and outer surface of anode 2 may be adapted to direct the flow from opening 13 on an inwardly sloping inclined path intersecting the first flow exiting opening 9, as shown by inclined dashed arrows I.
• the flow exiting through annular opening 13 may be used to combine material into the external portion of plasma arc P extending beyond opening 9.
• the proximity of the outer surface of anode 2 may allow material in this second flow to be heated before combination with the first flow.
• element 3 may be adapted to at least partially cover the lower surface of anode 2, such that the lower surface of element 3 becomes the lower surface of plasma head 10 and the second flow combines with the first flow before it exits plasma head 10.
• the lower end of element 3 and outer surface of anode 2 may be adapted to direct the flow from annular opening 13 to be more-or-less parallel to the flow exiting opening 9.
• Such an inert gas may be used to form a shield around the plasma arc exiting opening 9 and those regions of the work-piece surface 8 or deposited material 7 heated by the plasma arc.
• the shield flow is indicated by dashed arrows S in Figures 1 and 2.
• a second element may be adapted to provide an inert gas shield for the plasma arc exiting opening 9 and flow exiting opening 13.
• a range of operating conditions may be established to achieve full decomposition of at least a substantial fraction of one or more metal iodide flows, by appropriately configuring the temperature and pressure within those portions of the plasma arc traversed by the one or more metal iodide flows, the dwell time of the one or more metal iodide flows within traversed portions of the plasma arc, and the relative proportions of the mass flows of metal iodide and inert gas.
• Figure 1 shows material feeder 4, positioned to establish a flow comprising a metal iodide that combines with the first flow comprising an inert gas before the first flow has entered or completely traversed plasma generation volume 11.
• Such a configuration may allow a metal iodide flow to traverse a maximum portion of the plasma arc.
• a suitable material feeder may include a means for directing a stream of powder, liquid or gas, possibly premixed with a gas or other gas, and possibly preheated.
• material feeder 5 is shown positioned to introduce a flow comprising a metal iodide that passes through coaxial volume 12, exits opening 13 and, as shown schematically by dashed arrows I, combines with the first flow after the first flow has exited both plasma generation volume 11 and plasma head 10 to form external plasma arc P.
• the second flow might combine with the first flow after the first flow had exited the plasma generation volume 11, but before it had exited plasma head 10 to form external plasma arc P.
• the spatial extent, temperature and pressure distribution of the external portion of the plasma arc P, and the relative composition, mass flow and velocity profile of the flow exiting opening 13 at least a substantial fraction of the metal iodide flow originating with feeder mechanism 4 may be fully dissociated in the combined flow exiting plasma head 10.
• Figure 1 shows only two asymmetrically placed material feeders 4 and 5, fewer or more may be used, and they may be placed symmetrically with respect to the plasma head.
• One or more flows comprising different metal iodide may be established using one or more material feeders disposed as feeders 4 or 5. More than one metal iodide may be introduced in the same feeder to establish a combined flow of one or more metal iodides. The same metal iodide may be introduced using more than one feeder.
• Figure 2 also shows material feeder 15 external to the plasma head and positioned to combine a second flow comprising a metal iodide with the first flow in the external plasma arc P.
• material feeder 14 shown in Figure 2 would also be positioned to combine a second flow comprising a first metal iodide with the first flow in the external plasma arc P.
• Figure 2 shows only two asymmetrically placed material feeders 14 and 15, fewer or more may be used, and these may be placed symmetrically with respect to the axis of the plasma head.
• One or more metal iodide flows comprising one or more metal iodides may be established using one or more material feeders disposed as feeders 14 or 15.
• More than one metal iodide may be introduced in the same feeder to establish a combined flow of one or more metal iodides.
• the same metal iodide may be introduced using more than one feeder.
• Suitable metal iodide or iodides may be stored in solid form, for example, as powder in a hopper, or in the form of a liquid or gas.
• a supply of metal iodide may also be produced, as needed, by a suitable chemical process. (For example, Til 4 may be formed by reacting TiCI 2 with HI, or Ti with l 2 vapor.)
• a metal iodide flow comprising metal iodide substantially in a solid, liquid or gaseous state may be combined into the first flow.
• a flow comprising a solid metal iodide in powder form may be heated as it passes through coaxial volume 12, to form liquid or gas phase metal iodide before combination with the first flow, or the metal iodide may be preheated to form liquid or vapor before it is introduced from feeder mechanism 4.
• Feeder mechanisms such as those indicated as 4, 5, 14 and 15 may be used with materials other than metal iodides.
• a flow comprising particles of a seeding material, as described below, or metals that do not form suitable iodide compounds may be introduced. Gases other than inert gases, including hydrogen, as also described below, may also be introduced with such feeder mechanisms.
• an optional microwave source 18 typically an induction system operating at around a few GHz, may be used to deliver additional energy to the plasma stream or flow P or gas stream or flow G exiting the plasma head 10. (Plasma P, as opposed to gas G, is shown passing through source 18.)
• the power and frequency spectrum delivered by source 18 may be tuned to transmit energy to one or more specific metal-iodine bonds, in an effort to break apart residual non-decomposed metal iodide species.
• a deposited material 7 comprising one or more metals may be formed on at least a fraction of the region 8.
• the temperature of the deposited material 7 may be adjusted, for example, by varying the power and extent of the external plasma arc and the work-piece to plasma head distance, to ensure formation of a fully molten metallic deposit, or to suppress back reaction of solid or liquid metallic material with iodine.
• a reducing gas such as hydrogen, may also be introduced, optionally as part of the combined flow or with any of the metal iodide or other material flows, to react with the free iodine released by the decomposition of metal iodides or with residual any metal iodides.
• Feeder mechanism 16 shown in the figure may be, for example, a powder feeder or a wire feeder of known type.
• An additional heat source such as a laser, may also be used to increase the temperature of material deposit, and optionally apply heat to the additional material from a source such as feeder 16.
• the metal species formed by decomposition of one or more metal iodides in the plasma arc may be induced to condense to form solid or liquid clusters before coming into contact with the work-piece.
• a seeding material that promotes heterogeneous nucleation of metal clusters may be introduced into the combined flow.
• an appropriate seeding material may be introduced using means 4 shown in Figure 1 leading, through volume 12, into the inclined directed annular flow I, or using an introduction means external to the plasma head and directed towards external portion of the plasma arc P, shown as introduction means 15 in Figure 2, or directed towards gas flow G, shown as introduction means 14 in Figure 2.
• Suitable materials that may be used for seeding cluster condensation in metals include metal particles, such as Al, V, Si, B, Mo, Be and Ti, and ceramic clusters, such as TiB 2 , SiC, WC, BN, Y 2 0 3 , Zr0 2 .
• Seeding materials may be used in alloy deposition, for example, with Ti, Zr and Be alloys. The size distribution of seeding material particles may be optimized to ease handling and introduction into the combined flow, while providing a suitable density of nuclei.
• different combinations of metals and alloys may be deposited at different rates and at different times on the work-piece.
• Ti metal or alloys may be deposited
• Zrl 4 or Bel 2 Zr or Be metals or alloys may be deposited.
• the primary metal iodide may be pre- mixed with defined amounts of more than one other iodide before introduction of the mixture into the plasma system using one or more feeder mechanisms.
• more than one metal iodide may be introduced simultaneously into the plasma system using separate feeder mechanisms.
• separate feeder mechanisms and possibly iodides in different physical states, optimized to ensure the full decomposition of each iodide species.
• the feeder for the flow comprising Bel 2 an iodide for which the kinetics may be less favorable, may be configured to traverse a greater portion of the plasma arc and combine with the plasma arc with the iodide already vaporized, while the feeder for Til 4 , may be configured to be traverse a smaller portion of the plasma arc and combine with the iodide still in a solid phase.
• Suitable iodides for producing alloys include Vl 3 , All 3 , Zrl 4 , Bel 2 , Hfl 4 , Nbl 3 , Tal 3 , Bl 3 , Sil 4 , Sml 2 , Gdl 3 , Ndl 3 , Thl 4 , Mol 2 , Col 2 , Nil 2 , Mgl 2; Snl 4 and Cl 4 .
• the primary metal iodide flow is Til 4
• appropriate flows of Vl 3 and All 3 may be configured to deposit a Ti-6AI-4V alloy on the work-piece.
• metal iodides may be premixed and introduced using the same feeder or feeder mechanisms, or may be introduced in separate flows. Suitable combinations of metal iodide flows may also be used to deposit alloys of Zr and Be, with Zrl 4 or Bel 2 , respectively, comprising the first metal iodide flow, in place of Til 4 , and with suitable alloying components being introduced as one or more other metal iodide flows, including iodides selected from the group listed above.
• plasma sources may be furnished in a range of sizes and operating powers to accommodate a range of deposition rates.
• a plasma head of the type shown in Figures 1 and 2 with a power input between 1 and 10 kW, may provide a material deposition rate of up to around 1 kg/hour.
• the plasma head and work-piece may be enclosed within a chamber that is vacuum-pumped and/or flushed with an Inert gas.
• the vacuum chamber may be equipped with means for removing iodine vapor produced by the decomposition of the one or more metal iodides, or excess metal iodides, for example, by condensation on a suitably disposed cold surface.
• plasma head 10 is shown disposed a vertical distance Z H above a horizontal substrate or work-piece surface 8. In general, the plasma head need not be disposed vertically above the work-piece.
• the work-piece surface region 8 is also shown as significantly larger than the lateral dimension X D of deposited material 7, though this need not be the case.
• the plasma head may be operated such that only a small fraction of the flow of the gas or gas mixture exiting the plasma head actually reaches the work-piece, for example, by operating the plasma head vertically above the work-piece and maximizing distance Z G , such that a portion of the metal or alloy may reach the work-piece through the action of gravity.
• the combined flow rate, work-piece to plasma head distance Z H , internal and external plasma conditions, including the distances Z P and Z G , and composition of the flow mixture may be adjusted to deposit a metal or alloy powder onto the work-piece.
• Ti or alloy Ti alloy powder may be collected on a work-piece maintained at a sufficiently low temperature, typically no more than about 300 °C, to avoid the powder from coalescing, facilitating retrieval for possible use in additive manufacturing and other powder metallurgical technologies.
• the work-piece may be actively cooled to facilitate formation of a sufficiently friable powder agglomeration.
• the plasma head may be displaced and/or rotated relative to the work-piece in a controlled manner, and the work-piece may also be translated and/or rotated relative to the plasma head in a controlled manner, to facilitate access to different work-piece locations and allow deposition on selected regions.
• the thickness of the deposited material as shown by Z D in Figures 1 and 2 will be determined by the deposition time, and the lateral extent of the deposited material, as shown by X D in Figures 1 and 2, by the lateral extent of the material flow at the work-piece surface.
• uniform linear motion of a stable plasma source during deposition for example, from X 0 to Xi in Figure 1 may form a line of deposited material on work-piece surface 8, shown by the dashed lines representing intermediate stages.
• a series of abutting lines or points may be deposited on original work-piece surface 8, by controlled relative motion of work- piece and plasma head, to form a continuous or semi-continuous first layer of material having a complex lateral shape, as shown by feature 17 in Figure 2. Once allowed to solidify and cool, as necessary, such a first layer may provide a new surface for deposition of more material, as shown in Figure 2 by the location of deposited material 7 on first layer 17.
• a three-dimensional shaped component may be formed.
• the work-piece and plasma head may be used for additive manufacturing of metal or alloy components.

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Cited By (18)

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• 2012
  • 2012-04-13 WO PCT/EP2012/056798 patent/WO2013152805A1/fr not_active Ceased

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