WO2015192872A1

WO2015192872A1 - Methods for production of alloy wires and shaped alloy components from mixed metal halides

Info

Publication number: WO2015192872A1
Application number: PCT/EP2014/062560
Authority: WO
Inventors: David John Jarvis; Wayne Eric Voice
Original assignee: European Space Agency
Priority date: 2014-06-16
Filing date: 2014-06-16
Publication date: 2015-12-23

Abstract

A method of forming an alloy wire or shaped alloy component is described. A length of elongated core is exposed to a fluid mixture comprising two or more different metal halides, sufficient heat is applied to the length of halide-exposed elongated core to initiate dissociation of the two or more metal halides and maintained for sufficient time to deposit on the length of elongated core an alloy coating comprising the two or more metals, thereby forming an alloy wire. The elongated core may be coiled into a desired shape, optionally with the aid of a mandrel, allowing the formation of a shaped alloy component.

Description

METHODS FOR PRODUCTION OF ALLOY WIRES AND SHAPED ALLOY COMPONENTS FROM MIXED METAL HALIDES

FIELD OF THE INVENTION

The present invention relates to the manufacture of alloy wires and shaped alloy components.

BACKGROUND OF THE INVENTION Alloy wires and shaped alloy components can be expensive and difficult to produce using conventional methods, even when starting from widely available and inexpensive constituent elements, because of the large number of processing steps required. Many structural or functional alloys are therefore economically viable only in high value applications. Some brittle functional alloys are also impossible to produce as free-standing wires or shaped components using conventional methods.

For example, certain tubes made from Ti-alloys, which offer high specific strength and excellent corrosion resistance, are expensive because conventional processing requires refinement of the elemental constituents, ingot construction and a sequence of extrusions and heat treatments. As another example, wires made from brittle superconducting alloys such as NbTi are expensive because conventional processing requires refinement of elemental constituents, encapsulation of a powder mixture or ingot in a conducting matrix, and a sequence of extrusions, wire drawings and heat treatments.

The Van Arkel process, which dates from the 1920s, see U.S. Pat. No. 1,671,213, has been used to make small quantities of extremely pure elemental metals, principally Ti, Zr, and Hf, by dissociating the elemental metal iodide vapour on an incandescent wire. However, despite extensive efforts, including work with bulk metal ingots or plates in the presence of high-power plasma sources, see, e.g., US 2,768,074 (Nat. Res. Corp.) and GB 792,638 (Nat. Res. Dev. Corp.), no economically viable halide process has been developed for the production of alloy wires or shaped components. Titanium iodide has, however, been adopted as a source gas in plasma-enhanced chemical vapour deposition of the thin TiN coatings used in many semiconductor components. See, e.g., US 7,033,939. It would be advantageous to develop low-cost halide-based methods for producing alloy wires and shaped alloy components.

OBJECT OF THE INVENTION

It is an object of at least some embodiments of the present invention to provide low cost methods for producing wires and shaped components from a range of functional and structural alloys.

It is another object of the present invention to avoid the above-mentioned disadvantages of alloy wires and shaped alloy components made by conventional methods.

It is a further object of the present invention to provide an alternative to the prior art. SUMMARY OF THE INVENTION

Thus, the above-described objects and several other objects are intended to be obtained in a first aspect of the invention by providing a method for producing an alloy wire or shaped alloy component, the method comprising : exposing a length of elongated core to a fluid mixture comprising two or more different metal halides; applying to at least a portion of the length of halide-exposed elongated core sufficient heat to initiate dissociation of the two or more metal halides at the surface of the at least a portion of the length of elongated core; and maintaining the sufficient heat for sufficient time to deposit on the surface of the at least a portion of the length of elongated core an alloy coating comprising the two or more metals.

An alloy wire means a wire formed by coating the length of elongated core with the alloy comprising the two or more metals. An alloy wire need not have a circular or uniform cross section, a uniform composition along its length, or a uniform composition running from the elongated core to the surface of the alloy coating. A shaped alloy component means an alloy component having a shape other than that of an alloy wire, as a result of coalescence of alloy coating formed on different portions of the length of elongated core, and includes shaped alloy components in which at least part of the elongated core is retained or from which the entire elongated core has been removed from the alloy coating.

The length elongated core can take the form of a filament, wire, tape or strip, and may be part of a greater length of elongated core. The length of elongated core may be twisted, bent, curved or straight and may be coiled or wound into different forms, optionally with the aid of a mandrel. The length of elongated core should be sufficiently mechanically resilient, optionally with the aid of a mandrel, and chemically resilient to be compatible with the present methods. If needed, the elongated core should have sufficient mechanical resilience to provide the alloy wire or shaped alloy component with sufficient mechanical integrity for a desired application.

The at least a portion of the length of elongated core onto which the alloy coating is deposited may, during or after formation of the alloy wire or shaped component, react with or be at least partially dissolved into or intermixed with the alloy coating.

A fluid mixture includes a mixture in a liquid or gaseous state. A gaseous and/or liquid metal halide mixture may coexist with a metal halide or halides in the solid state. A mixture comprising two or more different metal halides means a mixture comprising at least a halide of a first metal and a halide of a second metal. The first and second metal halides may be formed from the same halogen, e.g., both may be iodides or both may bromides, though fluid mixtures involving different halides, e.g., one or more iodides and one or bromides are not excluded.

Applying sufficient heat to the at least a portion of the length of elongated core means applying sufficient heat to at least a portion of the length of elongated core by a range of means, including induction heating, radiation heating, exposure to a heated plasma, or resistive heating. Sufficient heat to initiate dissociation at the surface means enough heat to raise the temperature of the elongated core to a point at which the two or more metal halides at the surface of the elongated core begin to dissociate into their constituent halogen and metal components.

Maintaining sufficient heat for sufficient time to deposit on the surface of the at least a portion of the length of elongated core an alloy coating comprising the two or more metals means maintaining enough heat to continue dissociation— at the surface of the elongated core and at the surface of the growing alloy coating once it has covered the elongated core— the two or more metal halides which comprise the fluid halide mixture in order to deposit the alloy coating. The total amount and spatial profile of the heat applied to the at least a portion of the length of elongated core need not be constant during the deposition of the alloy coating and may be adjusted during the deposition process, as may other process conditions, such as the concentration and composition of the iodide fluid mixture and the longitudinal speed of the elongated core.

An alloy coating comprising the two or more metals includes alloy coatings in which the proportions of the two or more metals are related to, but not necessarily the same as, the proportions of the two or more metals in the fluid halide mixture.

Advantages of the present method include cost reduction, by directly manufacturing alloy wires and shaped alloy components from relatively low-cost halide feedstock, thereby avoiding costly conventional processing steps.

A further advantage of the present method is the ability to recycle the reaction products, partially or unreacted halides or halogens, into halide feedstock, leading to further cost reduction and other benefits. A yet further advantage of the present method is that, by selecting a given composition of the fluid halide mixture, e.g. one having given relative proportions of two or more given metal halides, and by adjusting the processing conditions appropriately, including the amount and spatial profile of the heat applied to a given length of elongated core, the composition and properties of the deposited alloy may be controlled and a broad range of functional and/or structural alloys may be deposited.

Another advantage is that alloys that are not amenable to formation into free- standing wires or shaped components by conventional methods— e.g., superconducting alloys such as NbTi that are so brittle that they are embedded in a conductive matrix before forming wire by a sequence of extrusions, drawings and heat treatments— may be produced using the present method. The length of elongated core may be passed in a substantially longitudinal direction through a first region of fluid halide mixture, in which the length is exposed to the fluid halide mixture. At least a portion of the length of halide-exposed elongated core may also be passed in a substantially longitudinal direction through a second region, in which the sufficient heat is applied to the at least a portion of the halide- exposed length.

Passing in a substantially longitudinal direction includes movement by drawing, e.g., pulling or pushing or both, without necessarily changing the diameter of the elongated core, and may include intermittent and/or continuous movement at a substantially fixed or variable rate. Passing the elongated core in a substantially longitudinal direction through a first region means movement with a substantially longitudinal component through the first region. Similarly, passing at least a portion of the elongated core in a substantially longitudinal direction through a second region means movement with a substantially longitudinal component through the second region. Passing in a substantially longitudinal direction includes movement in which the length of elongated core does not necessarily move along a perfectly straight path or remain perfectly straight.

An advantage of passing the length of elongated core in a substantially longitudinal direction though the first region, where it is exposed to the fluid halide mixture, and passing at least a portion of the halide-exposed elongated core through the second region, where heat is applied to at least a portion of the elongated core, is that the alloy coating process can be made continuous. Advantages of a continuous process for producing alloy wire may include a lower cost than batch processing and the ability to produce alloy wire in practically unlimited lengths, to the extent that such lengths of continuous elongated core are available.

The first region may be a liquid and/or gaseous reservoir of the fluid halide mixture.

The first and second regions may be disposed such that the length of elongated core is passed through the first region, in which the length of elongated core is exposed to the halide fluid mixture, before the at least a portion of the length passes through the second region, in which heat is applied to the at least a portion of the length of halide-exposed core.

The first region, in which the length of elongated core is exposed to the halide fluid mixture, may enclose the second region, in which heat is applied to the at least a portion of the length of halide-exposed core.

In the second region, the heat may be applied to at least a portion of the elongated core using, inductive, radiation or plasma heating. Resistive heating may also be applied.

The length of elongated core may be wound to form a coil, which means that the elongated core may be formed into a series of loops or turns that describe a coil having a desired shape. The loops or turns need not be uniform in pitch or diameter, need not all be of the same polarity, e.g., left-handed or right-handed, and may overlap or be in contact at certain points. The resulting coil need not define a simple geometrical shape, such as a cylinder or cone, e.g., the desired shape may be comprised one or more planar surfaces. Formation of coiled alloy wires having a desired shape, by depositing the alloy on an elongated core that is coiled into the desired shape before the alloy is deposited, may be advantageous in certain applications in which, e.g., the alloy wire, despite the presence of the elongated core, is difficult or impossible to coil into the desired shape without compromising the mechanical integrity or properties of the alloy coating. Where the elongated core is formed into a coil, the spacing between adjacent turns may be sufficiently small, and the alloy coating deposited to a sufficient thickness, that the alloy coating formed on the at least a portion of the length of elongated core may fuse to form a shaped alloy component. A sufficiently small spacing between adjacent turns of the uncoated elongated core includes configurations in which at least parts of the adjacent turns of the uncoated elongated core are in contact with or overlap each other before the coating is applied. The elongated core may be coiled to form a helix, including a circular helix having a constant diameter along its length, in which case, by depositing a sufficient thickness of alloy coating onto a coil having a sufficiently small spacing between adjacent turns, the shaped alloy component may be formed as a hollow tube of constant diameter. The elongated core may also be coiled to form a conic helix having a changing diameter along the length of the coil that defines a conic surface, in which case, by depositing a sufficient thickness of alloy coating, the shaped alloy component may be formed as a hollow tube with a constantly varying diameter along its length. The longitudinal axis of the helix, circular or conic, need not be perfectly straight, allowing the formation of shaped components having the form of curved or bent tubes.

The coiled elongated core may be supported by an appropriately shaped mandrel around which the elongated core is coiled. The material from which the mandrel is formed may be chosen to be sufficiently heat resistant and chemically neutral to withstand the halide deposition process without substantially decomposing or reacting with the halide mixture or its reaction products, including with the elongated core and alloy coating. The mandrel may also be chosen to have sufficient mechanical resilience to not lose its initial overall shape as a result of the halide deposition process.

An advantage of using a mandrel is that a coil can be formed from the elongated core and constrained by the mandrel to faithfully maintain its shape during and after the deposition of the alloy coating, such that the shape of the alloy component is defined by the shape of the mandrel, allowing the formation of alloy components in a range of shapes by use of an appropriately shaped mandrel. Once the alloy coating has been applied, the mandrel may be removed from the shaped alloy component, leaving the alloy component comprising the deposited alloy coating and coiled elongated core. The removal of the mandrel may be achieved mechanically and/or by a chemical process that does not detrimentally affect the alloy coating or elongated core.

An advantage of removing the mandrel after the alloy coating has been deposited is that free-standing alloy components may be produced, including hollow tubes, which may have constant or varying diameters along their length, and which may be bent or curved, by use of an appropriately shaped mandrel. In some applications, it may be advantageous to remove the mandrel but retain the coiled elongated core, e.g., to provide additional mechanical support for the shaped alloy component. An advantage of producing a superconducting alloy component in the form of a hollow tube is that the superconducting material of the tube may be cooled by passing coolant through the center of the tube, thereby reducing the need for additional tubing to carry any required coolant, and thus reducing the complexity and cost of the system in which the superconducting component is incorporated.

The elongated core may also be at least partially removed from the shaped alloy component, together with the mandrel. As for the mandrel, the removal of the coiled elongated core may be achieved mechanically or chemically by a process that does not detrimentally affect the alloy coating.

An advantage of removing the mandrel and coiled elongated core is the ability to form free-standing shaped alloy components consisting of deposited alloys having a desired composition. In the method of coating a coiled elongated core, the heat may be applied to at least a portion of the length of coiled elongated core by resistively heating the elongated core.

Resistive heating has the advantage that certain materials have seen widespread use in diverse heating applications, such that the heat delivery to cores made from such materials is extremely well characterized, including in configurations in which the core is in the form of circular helical coil having a uniform diameter and pitch, as in embodiments of the present method. Resistive heating is not limited to passing current along the length of the core. For example, a core which is coiled to form a tube may be heated by passing electrical current along the length of the tube, before and during the formation of the alloy coating.

The length of elongated core may be coiled about the longitudinal axis of an elongated mandrel to surround at least a portion of the length of the elongated mandrel, which may have a uniform cross section along its entire length. At least a portion of the length of elongated mandrel comprising the length of coiled elongated core may be passed in a substantially longitudinal direction through a first region in which the length of coiled elongated core may be exposed to the fluid halide mixture. At least a fraction of the at least a portion of the length of elongated mandrel comprising at least a portion of the length of halide-exposed elongated core may also be passed in a substantially longitudinal direction through a second region in which sufficient heat is applied to the at least a portion of the length of halide-exposed elongated core. Passing the elongated mandrel through a first or second region substantially in the longitudinal direction is intended to mean passing a length of elongated mandrel through a first or second region in a direction substantially corresponding to the longitudinal axis of the elongated mandrel, which need not correspond to the continuously varying longitudinal axis of the coiled elongated core.

An advantage of passing, in a substantially longitudinal direction, at least a portion of a length of elongated mandrel comprising the length of coiled elongated core though a first region, in which the length of coiled elongated core may be exposed to the fluid halide mixture, and of passing, again in a substantially longitudinal direction, at least a fraction of the at least a portion of the length of elongated mandrel comprising at least a portion of the length of halide-exposed elongated core through a second region, in which sufficient heat is applied to the at least a portion of the length of halide-exposed elongated core, is that the process may rendered continuous. An advantage of using an elongated mandrel in a continuous process is that shaped alloy components in the form of lengths of tubing, having circular or other cross sections, as defined by an appropriately shaped mandrel, may be produced which are limited in length only by the availability of a suitable length of elongated mandrel, assuming a sufficient length of elongated core is also available to form a coil of the desired configuration. The length of shaped alloy component formed using a continuous process can thus be significantly greater than the length of the first region, in which the length of coiled elongated core is exposed to the halide fluid mixture, and greater in length than the second region, in which heat is applied to the length of halide-exposed coiled elongated coating and the alloy coating deposited.

The two or more metals may be selected from the group consisting of Ti, V, Al, B, Zr, Nb, Ta, Hf, Th, Zn, Sm, Nd, Cr, Co, Ni, Cu, Mg, Gd, or Dy.

The elongated core may be comprised of a material selected from the group consisting of W, a W alloy, an FeCrAI alloy, a NiCr alloy or a NiCrFe alloy.

The metal halides in the fluid mixture may be selected from the group consisting of iodides and bromides.

Advantages of using iodides or bromides include the relatively low temperatures required to dissociate many iodides and bromides, and the relative ease of handling and recycling iodides and bromides and their reaction products, including iodine and, to a lesser extent, bromine.

BRIEF DESCRIPTION OF THE FIGURES

The figures show different ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 and 2 show schematically features of systems for performing a method according to the present invention. Figures 3A to 3D show schematically stages in a method for forming an alloy tube according to the present invention .

DETAILED DESCRIPTION

FIGS. 1 and 2 are schematic side views of parts of systems suitable for performing continuous alloy coating according to the present invention. In FIG. 1, elongated core 11 is shown being passed long itudinally at speed V through a reaction vessel 19. The fluid mixture of two or more metal halides in a gaseous state is shown being introduced into the reaction vessel by the arrow at through inlet 17. Though not shown in FIG. 1, the gaseous halide mixture may be formed in a variety of ways, includ ing by mixing two or more metal halides in their solid state by, e.g . , feeding suitable proportions of the solid metal iod ides, in the form of a powder or granules, into a hopper, and then heating the solid mixture to a temperature in an evaporation chamber connected to inlet 17 that is high enough for the halides in the solid, or possibly liq uid, state to vaporize to form a mixture of two or more metal halides in the gaseous state. The proportions of the two or more metal halides in the solid state need not be the same as, but may be related to, their proportions in the gaseous halide mixture in the reaction vessel . An inert carrier gas, e.g . , argon, may also be used to aid in the transport of the gaseous halide mixture from the evaporation chamber into reaction vessel 19.

With halide mixture in a gaseous state in reaction vessel 19, the surface of a length of elongated core 11 is exposed to the fluid halide mixture as it passes through the first reg ion enclosed by reaction vessel 19. Heat is shown being applied to at least a portion of the length of halide-exposed elongated core as it passes through a second reg ion where heat is applied to it by induction heater 16. In the system shown in FIG. 1, a portion of the length of elongated core first enters a first region, in which its surface is exposed to the gaseous halide mixture, and then enters and exits a second reg ion in which heat is applied, and finally exits the first region, which encloses the second region . If passage of the elongated core 11 is stopped, only a portion of the halide-exposed length will have passed through the heat- affected region . Deposition of the al loy coating 12 is shown schematically as occurring as a portion of the length of elongated core 11 enters through the region in which heat is applied . Though not shown in FIG. 1, for a given portion of elongated core, the thickness of the alloy coating may increase with the amount of time spent in the second region affected by the induction heater 16, as the portion of elongated core passes through the heat-affected region, from left to right in FIG. 1.

The mechanism or mechanisms used for passing the length of elongated core 11 in a substantially longitudinal direction are not shown, but may involve pulling and/or pushing. The length of elongated core, if sufficiently ductile, may be stored on a first reel before the alloy coating is applied, and the at least a portion of the length of alloy coated elongated core, i.e., alloy wire, if sufficiently ductile, may be collected and stored on a second reel. The speed V at which the elongated core 11 passes through the reaction vessel 19 may be varied in order to regulate the deposition of the alloy coating, e.g., by regulating the exposure time of the elongated core to the halide mixture and the time during which heat is applied to the at least a portion of halide-coated elongated core. Though not shown in FIGS. 1 and 2, a length of elongated core may be passed multiple times through a reaction vessel, in order to apply multiple layers of alloy coating, which may have the same or different compositions, depending on the processing conditions, e.g., the composition of the halide fluid mixture and the amount and profile of the applied heat. The composition of the alloy coating deposited on a portion of the elongated core may also be varied by changing the processing conditions during passage of the portion through the reaction vessel.

The arrow at outlet 18 indicates unreacted metal halide, partially reacted metal halide and/or halogen, predominantly though not necessarily entirely in vapour form and possibly accompanied by an inert gas, leaving the reaction vessel 19.

Though not shown in FIG. 1, outlet 18 may lead to a series condensers held at successively lower temperatures, first to precipitate out the metal halides and, second, to precipitate out the halogen. Halogen and metal halide condensates can be recycled and reused in the deposition method, in the case of the halogen or partially reacted metal halides, after reaction with metal to form a suitable metal halide.

Reaction vessel 19 and the solid halide evaporation chamber, not shown in FIG. 1, can be enclosed in a suitable furnace in order to ensure that the metal halide mixture remains in a gaseous state. In order to prevent the introduction of unwanted moisture or other contaminants, the furnace surrounding the reaction vessel may be filled with an inert gas, typically argon, to shield the entry point of elongated core and the exit point of the alloy wire from moisture and other contaminants. As noted above, inert gas may also be introduced into the fluid halide mixture.

In FIG. 2, a length of elongated core 21 is shown being passed at speed V through a reaction vessel 29. The fluid mixture of two or more metal halides in a liquid state is introduced into the reaction vessel by use of liquid reservoir 25. The surface of a length of elongated core 21 is exposed to the liquid halide mixture in a first region as it passes in a substantially longitudinal direction through the liquid reservoir 25, with heat then applied to at least a portion of the halide-exposed surface of the length of elongated core as it passes through a second region in which heat is delivered by an induction heater 26. In the system shown in FIG. 2, a portion of the length of elongated core 21 passes through the first region, in which the liquid halide mixture is applied, before it passes through the second region in which heat is applied by induction heater 26. In this configuration, if passage of the elongated core 21 is stopped, only a portion of the halide-exposed length will pass through the heat-affected region. In general, the heat source may be applied to the liquid layer 23 as soon as, or before, it exits liquid reservoir 25.

In FIG. 2, a portion of halide-liquid-coated elongated core 23 is shown extending outside the liquid reservoir 25, and the deposited alloy coating 22 is shown schematically as being formed as the halide-liquid-coated elongated core enters the second region in which heat is applied by induction heater 26. Though the thickness of liquid coating on the elongated core 23, and of the deposited alloy coating on the elongated core 22, are shown equal and constant, both may vary along portions of the length of the elongated core 21. For example, some evaporation of the liquid layer 22 may occur, without dissociation and formation of the alloy coating. The entry of the elongated core 21 into the liquid reservoir is not shown in detail.

In FIG. 2, the placement of induction heater 26 relative to the point on the moving length of elongated core at which deposition of alloy coating 22 is initiated is not intended to indicate a preferable configuration. The actual point at which the deposition of the alloy begins, together with the composition of the alloy coating and its eventual thickness, will all depend on the process conditions used, including the composition of the fluid halide mixture and the amount and profile of the heat delivered to the at least a portion of the length of halide-coated elongated core. In general, the type and configuration of the heat source may also affect the location where alloy deposition is initiated, and the composition and thickness of the alloy coating.

In FIG. 2, unreacted or partially reacted metal halide and halogen, predominantly though not necessarily entirely in vapour form, and possibly accompanied by an inert gas, are shown leaving the reaction vessel by the arrow at outlet 28, which may be collected and recycled using suitable condensers, as described above in connection with FIG. 1. For the system shown in FIG. 2, reaction vessel 29 may also be enclosed in a suitable furnace which may be filled with an inert gas, and an inert gas may be introduced into reaction vessel 29, as described above in connection with FIG. 1.

A hybrid system, including a gaseous halide mixture inlet as shown by 17 in FIG. 1, and a liquid halide mixture reservoir, as shown by 25 in FIG. 2, may be used. As a reminder, features, including the diameter and length of the elongated core, the diameter and length of the alloy coated core, and the size and shape of the reaction vessel, are not intended to be shown to scale in FIGS. 1 and 2. In general, a relatively fine-diameter elongated core, of the order of 100 Mm, may be coated with an alloy layer thicker than the core diameter.

An advantage of a continuous method, as shown schematically in FIGS. 1 and 2, and discussed below in relation to FIGS. 3A to 3D, is that, once suitable processing conditions have been identified, any available length of suitable elongated core can be formed into an alloy wire of a given thickness and composition. For a given elongated core and coating system, the continuous process may be stabilized and controlled by regulating processing conditions that include the composition of the halide fluid mixture to which the elongated core is exposed, the speed of longitudinal passage of the elongated core through the reaction vessel, the size of the reaction vessel, including the size and characteristics of the liquid reservoir, if used, and the amount of heat and heat profile delivered to the halogen-exposed elongated core.

In general, the elongated core, 11 and 21, need not be confined to lie in a horizontal plane, as shown in FIGS. 1 and 2, as it passes long itud inally through the first and second regions, and may instead l ie in a vertical plane or a plane of any orientation . The elongated core, 11 and 21, also need not move along a straight path nor be confined to a single plane as it passes through the first and second regions. Thoug h this is not shown in FIGS. 1 and 2, in order to increase throughput, a system may be configured to allow more than one elongated core to pass at the same time throug h a sing le reaction vessel . FIGS. 1 and 2 show use of an induction heater. Other forms of heat application may be employed, includ ing rad iation or plasma heating, in a suitably adapted reaction vessel . Resistive heating is also an option, with the size of the heat affected reg ion determined by the placement of suitable electrical contacts to the moving uncoated/coated elongated core.

FIGS. 3A, B, C and D show schematically stages in a method for forming a hollow alloy tube according the present invention . Such a hollow tube can be formed using a length of elongated core coiled around a mandrel as part of a continuous or batch process.

In FIG. 3A, a length of elongated core 31 is shown coiled around an elongated cylind rical mandrel 34. The elongated mandrel is made from a heat resistant and sufficiently chemically neutral and mechanically resilient material, typically a ceramic, to withstand the coating process. The elongated core is shown as forming a circular helix, though other types of coil may be used, in which the polarity of the turns need not be constant, i.e. , need not all be left-handed or right-handed . The circular helical coil is shown having a regular pitch between adjacent turns, though a regular pitch need not be used . The coiled elongated core need not evenly cover the entire surface of the mandrel . For example, holes or openings of a desired geometry may be defined in the shaped component by not extend ing the coiled elongated core across the entire mandrel surface. For clarity, in FIG. 3A, elongated core 31 is shown spaced away from the surface of elongated mandrel 34, though may be wound tightly to abut the surface of the mandrel. In general, the mandrel need not be cylindrical, i.e., need not have a uniform circular cross section and need not be elongated. A cylindrical or other elongated mandrel may also curved or bent to adopt a desired form, e.g., for use in the formation of a curved or bent hollow tube. If the elongated core is sufficiently resilient to support a free-standing coil, the mandrel may be dispensed with. In general, the mandrel need not be placed horizontally, as shown in FIG. 3, may be placed at any orientation relative to the horizontal and may be moved to a adopt a different orientation or rotated about a suitable axis during the coating process. The mandrel need not be cylindrical, as shown, and may have a range of shapes.

In general, an alloy coating may be deposited using a continuous process on the portion of the length of elongated mandrel 34 around which the length of elongated core 31 is shown coiled in FIG. 3 using a system of the type shown in FIGS. 1 and 2, with elongated mandrel 34 taking the place of elongated core 11 and 12 shown in FIGS. 1 and 2. An elongated mandrel may be passed in a substantially longitudinal direction, e.g., longitudinal with respect to the longitudinal axis of cylindrical mandrel 34, in the manner of elongated cores 11 and 21, as shown in FIGS. 1 and 2. In this manner, at least the portion of the length of mandrel around which the length of elongated core is coiled, and thus the length of elongated core 31, may be exposed to a halide fluid mixture in a first region, and sufficient heat for sufficient time may be applied in a second region to at least a fraction of the halide-exposed portion of mandrel, and thus to at least a portion of the length of halide-exposed elongated core 31, thereby depositing an alloy coating on the at least a portion of the length of elongated core.

If the mandrel is not sufficiently elongated, it may not be feasible to pass it through a reaction vessel having a first region, in which it is exposed to halide fluid mixture, and a second region, where it and the coiled elongated core are exposed to sufficient heat, in the manner shown in FIGS. 1 and 2, without use of a modified supporting and transport mechanism. As an alternative to continuous processing, one or more mandrels and their associated lengths of coiled heat resistant elongated core may be introduced into the first region and second region of a reaction vessel of the type shown in, e.g., FIG. 1, if suitably supported mechanically, allowing exposure to halide vapour and the application of sufficient heat for sufficient time to deposit the desired thickness of alloy coating. A coil or coils not supported by a mandrel having sufficient mechanical resilience could also be subject to batch processing. FIG. 3B shows alloy coating 32 having been deposited on the surface of the entire length of coiled elongated core 31, leaving the exposed ends of mandrel 34 protruding beyond alloy coating 32. Because the spacing between adjacent turns of the helical coil was sufficiently small, and the alloy coating was deposited to a sufficient thickness, the alloy coating 32 applied to adjacent turns of the coiled elongated core has fused to form a shaped alloy component. Though the ends of mandrel 34 are shown extending beyond the alloy coating, some alloy coating may form directly onto the mandrel surface, particularly in regions adjacent to the coiled elongated core. After cooling and removal from the reaction vessel, mandrel 34 may be removed, leaving a free-standing alloy component, in this case a hollow tube, as shown in FIG 3C, consisting of the length of coiled elongated core 31 and alloy coating 34. Removal of the mandrel may be done mechanically and/or chemically, such as by leaching using a suitable alkali, in any manner that does not detrimentally affect the properties of the shaped alloy component.

As shown in FIG. 3D, the coiled elongated core 31 may also be removed, mechanically or chemically, or by a combination of the two, to form a free standing alloy coating 32. Mandrel and coiled elongated core may be removed as part of the same process. However, in some applications, it may be advantageous to retain the coiled elongated core, e.g., to provide additional mechanical support for the shaped alloy component.

The length of halide-exposed elongated core coiled around the mandrel may be heated inductively, by a suitable radiation source, by a plasma source or resistively, as discussed above with regard to the systems shown in FIGS. 1 and 2. Resistive heating has the advantage that many core materials are widely used in heating application, and their properties are extremely well characterized, including when configured to form circular helical coils having a uniform diameter and pitch surrounding ceramic cylinders of given sizes and compositions. Suitable materials for the elongated core include W alloys, and include any of a series of well-known FeCrAI, NiCr and NiCrFe alloys. For example, relatively fine, 100 Mm diameter, W wire may be suitable for use when coiled with, or without, a mandrel. These materials may also be used in a continuous wire coating process of the type shown in FIGS. 1 and/or 2. A range of compatible ceramic materials for use in the mandrel are well known.

Though not shown as such in FIGS. 3A to D, the mandrel 34 and hollow alloy tube 32 need not be straight or parallel sided, and may adopt a variety of forms, with a curved or bent shape, according to the shape desired for the finished alloy component. This has the advantage that shaped components may be formed in a variety of custom shapes. For example, hollow tubes of constant or variable cross sections and diameters, curved or bent, as desired, may be formed by coiling a sufficient length of elongated core around an appropriately shaped mandrel. The wall thickness of such hollow tubes may also be varied along length of the tube, e.g., by varying the spacing of the turns of the coils along the length of the mandrel. Where the mandrel is sufficiently elongated for use in a continuous process, the thickness of the tube walls may also be varied along the length of the tube by regulating the processing conditions, e.g., by regulating the time a given portion of mandrel and elongated core spends in the heat affected zone.

An advantage of forming a hollow tube of superconducting alloy is that the superconducting material may be used to contain cooling fluid, thereby dispensing with the need for a separate structure to deliver cooling fluid to the superconducting material. Hollow tube structures having different diameters, optionally after coating with metal, as discussed below, may also be nested one within each other to provide a greater amount of superconducting material per unit length than may be available in any single hollow tube. The alloy wire or shaped component may be cleaned using well known techniques to remove any residual halogens or halides, including using water or organic solvent. A variety of metal coatings, including alloys, may be applied to the alloy wire or shaped component using a number of different known coating techniques. For example, superconducting alloy wires may be coated with Cu and/or Ag using electroless plating. The above-described methods may be used to form structural and functional alloys comprised of two or more of a range of metals, including Ti, V, Al, B, Zr, Nb, Ta, Hf, Th, Zn, Sm, Nd, Cr, Co, Ni, Cu, Mg, Gd, or Dy.

In particular, the above-described methods may be used to form alloy wires and shaped components from structural alloys— such as Ti-6AI-4V and other difficult to process Ti-based and other alloys— and functional alloys— including superconductors, such as niobium-titanium, thermo-electrics, magnetic alloys, and shape memory alloys, such as nickel-titanium— for use in a range of fields, including space, aeronautics, maritime, off-shore, automotive, chemical, and energy production.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

A method for producing an alloy wire or shaped alloy component comprising : exposing a length of elongated core to a fluid mixture comprising two or more different metal halides;

applying to at least a portion of the length of halide-exposed elongated core sufficient heat to initiate dissociation of the two or more metal halides at the surface of the at least a portion of the length of elongated core; and, maintaining the sufficient heat for sufficient time to deposit on the surface of the at least a portion of the length of elongated core an alloy coating comprising the two or more metals,

thereby forming the alloy wire or shaped alloy component.

The method of claim 1 :

wherein the length of elongated core is passed in a substantially longitudinal direction through a first region in which the length is exposed to the fluid halide mixture; and,

wherein the at least a portion of the length of halide-exposed elongated core is passed in a substantially longitudinal direction through a second region in which the sufficient heat is applied to the at least a portion of the length.

The method of claim 2, wherein the first region comprises a liquid reservoir of the fluid halide mixture.

The method of any of claims 1 to 3, wherein the first region comprises a gaseous reservoir of fluid halide mixture.

The method of any of claims 1 to 4, wherein the first and second regions are disposed such that the length of elongated core is passed through the first region before at least a portion of the length passes through the second region.

6. The method of any ones of claims 1 to 5, wherein the first region encloses the second region.

7. The method of any of claims 2 to 6, wherein the heat is applied using resistive, inductive, radiation or plasma heating.

8. The method of any of claims 1 to 7, wherein the length of elongated core is coiled.

9. The method of claim 8, wherein the spacing between adjacent turns of the coil is sufficiently small, and the alloy coating is deposited to a sufficient thickness, that the alloy coating deposited on the at least a portion of the length of elongated core fuses to form the shaped alloy component.

10. The method of claim 9, wherein the elongated core is coiled to form a helix and wherein the shaped alloy component has the form of a hollow tube.

11. The method of any of claims 8 to 10, wherein the coiled elongated core is supported by a mandrel.

12. The method of claim 11, wherein, after application of the alloy coating, the mandrel is removed from the shaped alloy component, leaving the alloy coating and the coiled elongated core.

13. The method of claim 12, wherein the coiled elongated core is also removed from the shaped alloy component.

14. The method of any of claims 9 to 12, wherein the heat is applied by resistively heating the elongated core.

15. The method of any of claims 11 or 14:

wherein the mandrel is elongated and the elongated core is coiled about the longitudinal axis of the mandrel;

wherein at least a portion of the elongated mandrel comprising the length of coiled elongated core is passed in a substantially longitudinal direction through a first region in which the length of coiled elongated core is exposed to the fluid halide mixture; and,

wherein at least a fraction of the at least a portion of the elongated mandrel comprising at least a portion of the length of halide-exposed elongated core is passed in a substantially longitudinal direction through a second region in which the sufficient heat is applied to the at least a portion of the length of halide-exposed elongated core.

16. The method of any of claims 1 to 15, wherein the two or more metals are selected from the group consisting of Ti, V, Al, B, Zr, Nb, Ta, Hf, Th, Zn, Sm, Nd, Cr, Co, Fe, Ni, Cu, Mg, Gd, or Dy.

17. The method of any of claim 1 to 16, wherein the elongated core is comprised of a material selected from the group consisting of W, a W alloy, an FeCrAI alloy, a NiCr alloy or a NiCrFe alloy.

18. The method of any of claims 1 to 17 wherein the metal halides are iodides or bromides.